Research ArticleEffect of Buckling Restrained Braces Locations onSeismic Responses of High-Rise RC Core Wall Buildings
Munir Ahmed1 Shahzadi Tayyaba2 and Muhammad Waseem Ashraf3
1Mohammad Ali Jinnah University Islamabad 44000 Pakistan2The University of Lahore Lahore 54000 Pakistan3GC University Lahore 54000 Pakistan
Correspondence should be addressed to Munir Ahmed drmunirjinnahedupk
Received 4 June 2015 Revised 14 September 2015 Accepted 27 September 2015
Academic Editor Marcello Vanali
Copyright copy 2016 Munir Ahmed et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
Conventionally a flexural plastic hinge is designed and detailed at the core wall base and coupling beams ends to control theseismic responsesThis strategy is based on allowing the damage to be concentrated onmain structural components To avoid suchdamage an alternative strategy using energy dissipating devices (EDDs) such as buckling restrained braces (BRBs) is being studiedand implemented nowadays In this study effect of BRBs locations on forty- (40-) story high-rise RC core wall case study buildinghas been studied in detail using Nonlinear Response History Analysis (NLRHA) for seven spectrally matched ground motionsBRBs have been installed at critical locations identified with respect to the maximumDBE elastic modal racking shear deformationdemands and force (shear and moment) demands in three different options The force deformation and energy demands onstructural components are compared for conventional design and different options of BRBs The comparison with conventionaldesign shows that BRBs not only are effective for reducing shear force demand along wall height bending moment demand at midheight and deformation demands by 10 45 and 45 respectively but significantly reduce the rotation and energy demands inthe core wall by 90 and 250 respectively
1 Introduction
High-rise reinforced-concrete (RC) core wall buildings arebeing built in areas of high seismic hazardThe structural sys-tem of these buildings is classified as building frame system asper Uniform Building Code [1] For reasons of economy lessconstruction time and flexible architecture these systems arepreferred over other lateral-force-resisting systems for exam-ple dual structural systems [2 3] The core wall buildingsconsist of central corewall and peripheral columns connectedby the posttensioned slabs at each story Sometimes core wallis also connected to the outer columns through one- or two-story deep outriggers to control the lateral displacementsThestiffness of the core wall is much higher than the combinedstiffness of the peripheral columns Therefore lateral loadis mostly resisted by the core wall For both design basisearthquake (DBE) and the maximum considered earthquake(MCE) levels it is uneconomical to design these walls in
the elastic range Under such severe shakings flexural singleplastic hinge (SPH) is designed and detailed at the core wallbase and coupling beams ends to reduce the seismic demandsHowever the plastic rotation in the hinge zonemust bewithinan acceptable limit The wall above the hinge zone and theother portion of coupling beams is expected to remain elastic[4ndash8]
Recent studies on a 60-story and 40-story RC core wallbuildings with SPH at the base in high seismic areas showthat the base shear demand at MCE level is as high as 15ndash20of the total building weight Furthermore bending momentdemands at upper levels shall be almost double compared tothat at the base level [9ndash11] To address these large shear andmoment demands the design may not be economically justi-fied for rare event of an MCE earthquake level Furthermoreproblem of reinforcement placing may arise due to rein-forcement congestion Therefore these demands need to bereduced by different possible measures
Hindawi Publishing CorporationShock and VibrationVolume 2016 Article ID 6808137 15 pageshttpdxdoiorg10115520166808137
2 Shock and Vibration
X
Y
Plan of the building 3D view of the building87
m87
m72
m72
m
72m3
Figure 1 Plan and 3D model of the building
Several approaches were proposed to reduce thesedemands One approach is to allow the wall to yield at anylocation along its height This approach is referred to asDuctile Wall (DW) approach and was proposed by [12] Thisapproach is uneconomical due to stringent ductile detailingrequirements all along the wall height Furthermore thesebuildings may not be economically repairable due to spreadof damage in a seismic event The second approach is DualPlastic Hinge (DPH) approach in which one hinge is allowedat mid height in addition to the plastic hinge at the base [13]This approach is effective only for reduction of 2nd modebending moment demand at mid height of the wall Anotherapproach in which plastic hinges were allowed at severaleffective locations was proposed by [14ndash16]
However in all the above-mentioned approaches damageis allowed in main structural components such as shearwalls and coupling beams To avoid this another strategywhich incorporates energy dissipating devices (EDDs) in thestructural system to reduce the inelastic energy dissipationdemand on the framing system [17 18] has been introducedIn this strategy the structural components may remain elasticor suffer less damage during an earthquake the structural andnonstructural damage may be considerably reduced Thesedevices were incorporated in a number of new buildings andwere used to retrofit existing buildings to reduce the windand seismic induced responses [19 20] Buckling restrainedbraces (BRBs) are one of the proven choices as EDDs forreducing seismic response reduction In Japan BRBs havebeen used successfully for many projects in retrofitting ofthe existing buildings as well as design of new buildingsHowever in the United States (US) their use is reported in 30buildings including retrofitting of the existing buildings andnew construction [21 22] (Black et al 2004 Keten 2006)
Their recent use in high-rise buildings is reported in a 60-story One Rincon Hill Building in San Francisco [10] and 50-story tall ductile core wall building in Philippines [23]
In this study effect of BRBs locations on 40-story high-rise RC core wall case study building is studied in detailusing Nonlinear Response History Analysis (NLRHA) BRBshave been placed at critical locations in cut in shear wallsand between peripheral columns and shear wallsThe criticallocations are identified based on DBE elastic racking sheardeformation demands and force demands The comparisonbetween different options in terms of force (shear force andbendingmoment) deformation (displacement racking sheardeformation and plastic hinge rotation in wall) and energydemands has been shown
2 The Case Study Building andElastic Modal Demands
21 Description of the Case Study Building The building istaken fromprevious research studies [9ndash11 14ndash16]The typicalfloor plan of the building and 3Dmodel are shown in Figure 1This is a 40-story residential tower above the ground withthree levels of below-grade parking The typical story heightis 3m and a lobby-level height is 6m Thus the total heightof building above ground is 120mThe building is supportedby a thick foundation slab to transfer load on a firm groundThe soil condition beneath and surrounding the building isrepresented by stiff clay soil This is equivalent to the soiltype SD in the UBC-97 [1] The structural components of thebuilding are comprised of a central RC core wall thickness(750mmTH up to Level 20 and 600mm thick form Levels 21to 40) 14 peripheral columns (900mm times 900mmup to Level
Shock and Vibration 3
0
05
1
15
2
25
3
35
Response spectra of scaled ground motionsSH-PR-360 times 30HM-H-090 times 40LP-HSP-000 times 15CM-EUR-090 times 40Hon-MGH-EW times 40Chichi-Taipei-090 times 60Imp-Ch-012 times 40
DBE spectrum (UBC-97 zone 4 SD)MCE spectrum (DBE spectrum times 15)
0
05
1
15
2
0 1 2 3 4 5 6 7 8 9 10Natural period (s)
0 1 2 3 4 5 6 7 8 9 10Natural period (s)
Spec
tral
acc
(g)
Spec
tral
acc
(g)
Target spectra
Figure 2 Comparison of the matched spectra of the groundmotions with DBE and MCE spectra
20 and 600mm times 600mm from Level 21 to Level 40) and200mm-thick posttensioned concrete flat slabs resting on theperipheral columns and the central core wall There are dooropenings in the wallThese openings are covered by couplingbeams The size of coupling beams is 600mm times 1500mmabove lobby level and 750mmtimes 800mm fromLevel 3 to Level20 whereas it is 600mm times 700mm from Levels 21 to 40Thecompressive strength of concrete for columns and walls is setto 55MPa up to Level 20 and 42MPa from Level 20 to theroof The reinforcing bars are Grade-60 steel with specifiedyield strength of 420MPa The central core wall forms thelateral load resisting system whereas posttensioned slabsand peripheral columns shall mainly form the gravity loadresisting system The gravity load includes self-weight of thestructure dead loads of 192 kNm2 and live loads of 24 kNm2
22 DBEElasticModal Demands byModal Response SpectrumAnalysis The modal response spectrum analysis (MRSA) ofthe building is performed using UBC-97 [1] design basisresponse spectrum for seismic zone-4 and soil type SD for5 damping in the single mode of vibration The responsespectrum is shown in Figure 2 The building is analysed in
the119883-direction only for brevity and considered sufficient forthe purpose of this study The commercial software ETABS[24] is used for MRSA procedure First six modes are foundto be sufficient for 90 mass participation in the MRSAHowever results show that both shear and moment demandsare mainly dominated by first four modes The combineddemands are obtained by combining individual modaldemands using CQC method
DBE elastic demands in the core wall in first four domi-nantmodes as well as their combination are shown in Figures3(a) 3(b) 3(c) and 3(d) respectively Both shear andmomentdemands are dominated by 1st 2nd and 3rd mode whereasdeformation demands are dominated by the 1st mode onlyThese demands shall be used for preparation of model forNonlinear Response History Analysis and to find the criticallocations of the BRBsThe story racking deformation angle isthe shear deformation of the panel between wall and periph-eral columnsThis is equal to the conventional story drift ratiosubtracted by the floor inclination angle measured clockwisefrom a horizontal plane
3 Description of Model forNonlinear Response History Analysis andSelection of Ground Motions
The nonlinear model is implemented in Commercial Soft-ware Perform-3D [25] The core wall is modelled using 22one-story high (3m) inelastic shear wall elements at theplastic hinge location at the base Each shear wall element wascomprised of 8 concrete and 8 steel fibres at the plastic hingelocations whereas the wall at other locations is modelled asthe 22 linear elastic shear wall elements The previous studies[26 27] show that plastic hinge length of the high-rise wallmay be taken as 12 to 23 times wall length (Lw) The lengthof the wall in this case is 10m Therefore plastic hinges wereallowed over two-story height (6m) which is approximately23 Lw However one-story high inelastic shear wall elementswere used over the plastic hinge length based on section68222 of FEMA-356 [28] which mentions that plastichinge length should be smaller than one-story height or Lw2
The flexural strength at the plastic hinge location shouldbe as low as possible to allow early yielding of the wall but atthe same time plastic hinge rotation as well as related defor-mation demands such as story drift and racking shear defor-mation should bewithin permissible limits In this study flex-ural strength is based on the DBE design moment demandsdetermined by code based procedure of UBC-97 [1] Theseare larger than the values obtained either (a) by dividing thecombined elastic demands by appropriate response modifi-cation factor ldquo119877rdquo of 55 or (b) by dividing ldquo119877rdquo factor requiredto satisfy the requirement of 90 of the base shear obtainedfrom static analysis procedure There are mainly two reasonsfor setting flexural strength in this way (1) this is based on thestandard code based design such as UBC-97 [1] (2) moderncode such as LATBDC-2008 [29] recommend capacity designas a first step of the performance based design and designersare using the code based design as the initial step and later
4 Shock and Vibration
minus5
0
5
10
15
20
25
30
35
40
0 3 6
Leve
l num
ber
CombinedMode-1Mode-2
Mode-3Mode-4
Moment (kNmiddotm times 106)
(a)
minus5
0
5
10
15
20
25
30
35
40
Leve
l num
ber
0 50 100
CombinedMode-1Mode-2
Mode-3Mode-4
Shear (kN times 103)
(b)
minus5
0
5
10
15
20
25
30
35
40
0 025 05 075 1
Leve
l
Displacement (m)
CombinedMode-1Mode-2
Mode-3Mode-4
(c)
minus5
0
5
10
15
20
25
30
35
40
Leve
l
0 001Racking shear deformation ratio
002
CombinedMode-1Mode-2
Mode-3Mode-4
(d)
Figure 3 DBE elasticmodal and total seismic demands (a)Moment demands (b) shear demands (c) displacement demands and (d) rackingshear deformation demands
confirm the performance at MCE level by the NLRHAprocedure
Plastic hinges are also induced at both ends of cou-pling beams The characteristics of the plastic hinges aredetermined by beam cross section properties and flexural
reinforcement worked out based on the design demands andassumed plastic hinge length of 05 times the depth of thebeam The remaining portion of the coupling beam is mod-elled as elastic beam element A trilinear moment-curvaturerelationship without stiffness and strength degradation is
Shock and Vibration 5
Stre
ss
Strain
Stre
ss
Strain
Unloading and reloading arethe same in case of tension
Steel material Concrete material
Mander envelopePerform-3D UnloadingReloading
f998400cc
Eo
EoEo
dcEo
120585998400cc120585998400c120585cu
ft
fu
fy
Park envelopePerform-3D Cyclic
120585y 120585sh 120585u
fy rebar yield stressfu rebar ultimate stress capacity120585y rebar yield strain120585sh strain in rebar at the onset of strain hardening120585y rebar ultimate strain capacityEo modulus of elasticiy
f998400c compressive strength of unconfined concrete
f998400cc compressive strength of confined concrete
120585998400c concrete strain atf998400c
120585998400cc concrete strain atf998400cc
120585cu ultimate strain capacity for confined concreteEo tangent modulus of elasticitydc energy dissipation factor for the reloading stiffnessft tensile strength of concrete = 75radicf998400
c (f998400c is in psi)
Figure 4 Nonlinear Park Steel and Manderrsquos concrete model
used for modelling plastic hinges at the ends of couplingbeams All slabs and columns aremodelled by elastic slab andcolumn elements of the Perform-3D respectively
Seven set of ground motions are selected from PEER[30] and COSMOS [31] data bases The ground motionsinclude both short distance moderate and long distancelarge magnitude earthquake The selected ground motionsare first roughly scaled up or down by a constant factor toapproximately match the target MCE spectrum The roughlyscaled ground motions are then matched to the MCE targetspectrum by using time domain spectral matching techniqueof [32] The software RSP match [33] is used for this purposeThe target spectrum and spectra of seven spectrally matchedtime history used in this study are shown in Figure 2 Non-linearmaterial models similar to those proposed by [34] wereassigned for rebarrsquos and concrete material respectively asshown in Figure 4 The modal damping is set as per recom-mendations of [35] CTBUH (2008) and [36]
4 Analysis of Structure without BRBs
The controlled structure described in Section 3 is analysedfor seven sets of ground motions The shear and momentdemands obtained are shown in Figure 5 These results showthat base shear demand is about 15 of the total building
weight Similarly moment demand is also very high at midheight However at the base the moment demand is clippedto the flexural strength of plastic hinge If the wall is designedfor mid height moment to remain elastic and hence nodamage there shall be reinforcement congestion On theother hand if plastic hinge is allowed at mid height the corewall shall be subjected to high rotational demands and hencedamage near themid height of thewall in addition to the baseTo reduce damage at the base of the wall as well as reducemid height moment to avoid reinforcement congestion analternative strategy using different arrangements of buck-ling restrained braces (energy dissipating devices) has beenevolved in the next section (Options-2ndash4) and results arecompared with the controlled structure (Option-1)
5 Buckling Restrained Braces Evolvement ofStrategies for Efficient Locations Their Sizeand Modelling
51 Buckling Restrained Brace An ordinary brace exhibitsunstable hysteretic behaviour due to buckling in compres-sion hence it cannot dissipate much energy To avoid com-pression buckling and to achieve more energy dissipationanother brace known as buckling restrained brace (BRB) hasbeen introduced This type of brace exhibits stable hysteric
6 Shock and Vibration
0 40 80 120
Mean MCE demands Mean MCE demands
0 1 2 3minus5
0
5
10
15
20
25
30
35
40
Leve
l num
ber
minus5
0
5
10
15
20
25
30
35
40
Leve
l num
ber
Shear (kN times 103) Moment (kNmiddotm times 106)
Figure 5 Inelastic MCE shear and moment demands in the controlled structure
Encasing mortar
Yielding steel core
Steel tube
Unbonding materialbetween steel core
and mortar
Figure 6 Typical BRB
behaviour because its compression buckling is avoided due toencasing by an outer steel tubeThemain brace and outer tubeare separated by bonding material in order to accommodatethe lateral expansion due to its compression yielding [37] Atypical BRB is shown in Figure 6 [38]
52 Location of Buckling Restrained Braces BRBs have beeninstalled at several critical locations based on the results ofelastic modal decomposition analysis in dominant modessuch as 1st 2nd and 3rd modes and results are comparedwith controlled structure described in Section 4 (Option-1)In second option (Option-2) the BRBs have been installed
at bays 2 3 and 4 between peripheral columns and centralcore wall based on the maximum racking shear deformationdemands in 2nd and 3rd modes This arrangement is shownin Figure 7 In third option small size BRBs have also beeninstalled at bays 2 and 4 in cut in central core wall at the max-imum moment demands in 2nd and 3rd modes These BRBsare in addition to the BRBs in Option-2 This arrangementis shown in Figure 8 In final and fourth option (Option-4)BRBs have been installed in cut in central core wall at bays 2and 4 at the location of maximum shear force in 2nd and 3rdmodes in addition to the BRBs in Option-2 This is shownin Figure 9 It may be noted that the locations of BRBs in
Shock and Vibration 7
0
5
10
15
20
25
30
35
40
0
000
1
000
2
000
3
000
4
000
5
Leve
l
Racking shear deformation ratioMode-2Mode-3
Mode-4
Figure 7 Arrangement of the BRBs at locations of maximum racking shear deformation in exterior panels (Option-2)
0
5
10
15
20
25
30
35
40
0 1 2 3
Leve
l
0
5
10
15
20
25
30
35
40
Leve
l
Mode-2Mode-3
Mode-4 Mode-2Mode-3
Mode-4
Moment (kNmiddotm times 106)
0
000
1
000
2
000
3
000
4
000
5
Racking shear deformation ratio
Figure 8 Arrangement of the exterior BRBs at locations of maximum DBE elastic racking shear deformation in 2nd and 3rd mode andinterior BRBs at locations of maximum DBE elastic moment demands in 2nd and 3rd mode (Option-3)
8 Shock and Vibration
0
5
10
15
20
25
30
35
40Le
vel
0
5
10
15
20
25
30
35
40
0 50 100
Leve
l num
ber
Shear (kN times 103)
Mode-2Mode-3
Mode-4 Mode-2Mode-3
Mode-4
0
000
1
000
2
000
3
000
4
000
5
Racking shear deformation ratio
Figure 9 Arrangement of the exterior BRBs at locations of maximum DBE elastic racking shear deformation in 2nd and 3rd mode andinterior BRBs at locations of maximum DBE elastic shear demands in 2nd and 3rd mode (Option-3)
Option-1 Option-2 andOption-3 are also suitable for mode-1
The BRBs dissipate energy through axial tension andcompression To achieve maximum energy dissipation theBRBs should be placed at the proper locations and anglesEach BRB has been placed at an angle of approximately1205874 covering almost three stories for exterior brace and twostories for brace in cut in core wall These V-shaped BRBsconfigurations resemble the BRBs configuration used inmegabraced frames steel buildings reported in the previous studies[39ndash41] BRBs shall cross the slabs through purposely builtopenings provided in the slabs A horizontal drag elementis used from point where BRB connects to the column tothe central core wall to take care of the horizontal forcecomponent of the BRB axial force at column connection
53 Size of Buckling Restrained Braces Sizes of the BRBs havebeen selected by hit and trial using more rigorous nonlineartime history analyses (NLTHAs) using displacement-baseddesign approach Their size should neither be too large tobe uneconomical nor be too small to be ineffective The 119883-section of the braces between peripheral columns and centralcore wall is selected as 7500mm2 whereas it is 3750mm2for braces in cuts in core wall The buckling restrained bracesmanufactured by star seismic with normal yield strength of280MPa are used for braces between peripheral columnsand central core wall [42] However the low yield point-100(LYP100) steel core manufactured by Nippon Steel Corpora-tion Japan with specified yield strength of 100MPa is used
f
0DXDU
FY
FUO
FUH
KF
KO
Figure 10 Trilinear curve for BRBs
for braces in cut elements [22]The lowyield point steel bracesare used in cut in core wall to mainly achieve more energydissipation through the early yielding of the brace [43]
54 Modelling of Buckling Restrained Braces A BRB consistsof three components that is central yielding core brace endsmember connecting the central brace with the pin connec-tion and pin connection between brace and main structuralmembers The length of the exterior core brace is 45mwhereas length of the core brace in cut of core wall is 18mThese lengths are in the optimum range of 02ndash04 times thetotal length of the brace Several advantages such as simple
Shock and Vibration 9
minus4000
minus3000
minus2000
minus1000
0
1000
2000
3000
4000A
xial
forc
e ( k
N)
Axial def (m)
10E minus 0150E minus 0200E + 00minus50E minus 02
(a)
minus500
minus400
minus300
minus200
minus100
0
100
200
300
400
500
Axi
al fo
rce (
kN
)
Axial def (m)
20E
minus03
10E
minus03
00E
+00
minus30E
minus03
minus20E
minus03
minus10E
minus03
(b)
Figure 11 Typical cyclic response of BRBs obtained from the analysis (a) Exterior brace (b) interior brace
replacement lesser weight concrete elimination economyand easy erection process are associated with reduced lengthof the core brace [44ndash50] BRB has been modelled using theBRB compound component of the Perform-3D Such mem-ber is composed of three components that is (1) a BRB basiccomponent for main yielding brace (2) an elastic bar basiccomponent for member connecting brace with gusset plateand (3) a stiff end zone which accounts for the gusset platesand so forth at both ends of the member
The positive side (tension) of the trilinear curve to definethe force-deformation of the BRBs is shown in Figure 10 Itcan be seen that after yielding there are two lines such asbottom and top line The bottom line is used to simulate firstcyclic load and the top line is used to simulate full strainhardening The same behavior has been observed in testslike the hysteresis loop which can progressively grow in sizeThis is sometimes referred to as ldquoisotropic hardeningrdquo Thisleads to the component increase in strength under cyclic loadThe negative side of the curve shows a little variation due todifference in the values of compression and tensions FY FUO(FUO (T) = 105 FY FUO (C) = 104 FY) and FUH (FUO(T) = 134 FY FUO (C) = 151 FY) are yield strength strengthat first loading cycle and strength of the core brace afterfull hardening respectively DU (DU (T) = 07 DU (C) =07) is the deformation at FUO and DX (DX (T) = 004 LYCDX (C) = 004 LYC) is the maximum deformation of thebrace LYC is the length of the yielding core KO is theInitial stiffness of the core brace and KF (= 002KO) is theslope of third line [42] The strain hardening properties suchas deformation at FUO-FUH average are taken equal to 2times (LYC180) and deformation at FUH is taken as 35times (LYC180) The typical force-deformation relationshipfor exterior (between peripheral columns and core wall) andinterior BRB (in cut in core wall) obtained from NLRHAanalysis for a particular ground motion is shown in Figures11(a) and 11(b) respectivelyThese figures show that hysteresisloop is similar to the reported Clark et al 1999 [38] provingthat performing BRB element can capture the behaviour
appropriately The size of the elastic bar element is selectedsuch that it can safely carry maximum axial force in brace inelastic range to conform to the capacity design approach Stiffend zone is few times stiffer than the elastic bar element
6 Comparison of the Responses in DifferentOptions and Discussion on the Results
NLRHA is performed using seven spectrally matched timehistories Different response quantities such as displacementplastic hinge rotations in coupling beams and core wall sheardeformation angle (story racking shear deformation) bend-ing moment shear force and energy demands are obtainedfrom this analysisThe plastic rotations are calculated bymul-tiplying the average curvature of the wall at mid height withthe plastic hinge length The mean value of different quan-tities obtained from seven ground motions are shown anddiscussed in following paragraphs
Shear demands obtained from four options are shownin Figure 12(a) Shear demand pattern and magnitude aresimilar in all options Moment demands obtained from fouroptions are shown in Figure 12(b) The moment demand atthe base is similar in all four options because this is clippedto the flexural strength of the plastic hinge at the base of thewall However it is reduced along the wall height by 30 35and 40 in Option-2 Option-3 and Option-4 respectivelyin comparison to that in 1st optionThe reduction inmomentdemand is significant in all options This will help to avoidreinforcement congestion in the wall near mid height
Displacement demands obtained from four options areshown in Figure 13(a) Displacement demand pattern is simi-lar for all options However displacement demand is reducedalong thewall height by 40 40 and 60 inOption-2 Option-3 and Option-4 respectively in comparison to that in 1stoption Racking shear deformation demands obtained fromfour options are shown in Figure 13(b) The racking sheardeformation demand patterns are similar for all four optionsHowever racking shear deformation demands are reduced
10 Shock and Vibration
minus5
0
5
10
15
20
25
30
35
40
0 50000 100000 150000
Leve
l
Shear force (kN)
Option-1Option-2
Option-3Option-4
(a)
minus5
0
5
10
15
20
25
30
35
40
Leve
l
0 1 2 3
Option-1Option-2
Option-3Option-4
Bending moment (kNmiddotm times 106)
(b)
Figure 12 MCE inelastic shear and moment demands in different options (a) Shear (b) moment
0 05 1 15 2 25Displacement (m)minus5
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(a)
0 001 002 003 004Racking shear deformation ratio
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(b)
Figure 13 MCE inelastic displacement and racking deformation demands in different options (a) Displacement (b) racking sheardeformation angle
along the wall height by 40 40 and 65 in Option-2Option-3 and Option-4 respectively in comparison to thatin 1st option This is significant reduction Racking sheardeformations of 0036 in the controlled structures are reducedto 0023 which is well within the limit of 003 set by [29]LATBSDC 2008 for the MCE level earthquake
Rotational demands in the core wall at the base level aswell as in coupling beams along the height are shown in Fig-ures 14(a) and 14(b) respectivelyThe rotation demand in thewall is calculated by multiplying the average curvature at themid height of the inelastic wall element by height of the wallThe comparison shows that themaximum rotational demand
at the base of the wall is reduced by 99 57 and 93 inOption-2Option-3 andOption-4 respectively in comparison to thatin 1st option This is strong indication that damage at thebase of the wall shall be reduced to half and consequentlyextent of repair shall be small and hence cheap in case ofsevere MCE events such as DBE and MCE level earthquakeThe rotational demands in coupling beams are reduced by52 40 and 35 respectively above the half height level forOption-2 Option-3 and Option-4 respectively in compar-ison to 1st option However rotation demand remained thesame in the lower half portion of the building for all options
Energy dissipated by core wall coupling beams andbuckling restrained braces have been compared in Figures15(a)ndash15(d) respectively for Option-1 Option-2 Option-3 and Option-4 respectively This is energy dissipated inpercentage of the total energy demand in the structure Thetotal energy demand is sum of the kinetic energy elasticstrain energy energy dissipated by elastic modal dampingand energy dissipation by damage in structural elements suchas core wall coupling beams and BRBs About 83 9292 and 90 energy have been dissipated by elastic modaland inelastic damping in Option-1 to Option-4 respectivelyThe energy dissipation by modal elastic damping to the totalenergy demands is 50 37 35 and 33 respectively inOption-1 to Option-4 respectivelyThe energy dissipation bycore wall at the base to the total energy demands is 22 66 and 6 inOption-1 to Option-4 respectivelyThe energydissipation by coupling beams to the total energy demands isapproximately 10 4 5 and 6 in Option-1 to Option-4 respectively The energy dissipation by BRBs to the total
energy demands is 0 45 45 and 45 respectively inOption-1 to Option-4
7 Effects of BRBs on Axial Loads Shearand Moment of Columns and PermanentDeformation due to BRBs Plastification
Effects of BRBs on axial loads of columns and permanentdeformation due to BRBs plastification have been discussedin this section The axial load envelope in a typical columnfor Options-1ndash4 is shown in the Figure 16 The magnitude ofaxial load is same for Options-2ndash4 (with BRBs) and is twicethan that in Option-1 (controlled structure) This is due tothe outrigger effect created by the connection of columnsand core wall through BRBs Some core wall moment hasbeen resisted by the development of axial push-pull in thecolumns Furthermore the shape of the axial load envelopeis smooth in case of Option-1 whereas it is jagged at thelocations of the BRBs forOptions-2ndash4Themoment envelopeand shear envelope for one typical column are shown inFigures 17(a) and 17(b) respectively It shows that momentand shear have been reduced at the ground level in Options-2ndash4 in comparison to Option-1 whereas these remain almostthe same at upper portions The extra moment and shearat the ground level in Options-1ndash4 is due to the transfer ofmoment and shear to the columns when core wall yields
To better understand the permanent deformation in thestructure due to BRBs plastification cyclic pushover analysisin firstmode is performedusing target displacement obtainedfrom NLTHA for all cases The cyclic base shear versus top
12 Shock and Vibration
Option-1
0
20
40
60
80
100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 53478kNmiddotm
(a)
Option-2
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 73328kNmiddotm
(b)
Option-3
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80 90
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 71449kNmiddotm
(c)
Option-4
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 69558kNmiddotm
(d)
Figure 15 Inelastic energy demands in structural components (a) to (d) For Option-1 to Option-4 respectively
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus20000 minus10000 0
Leve
l
Axial load (kN)
Option-1Option-2
Option-3Option-4
Figure 16 Axial load envelope in one typical column
Shock and Vibration 13
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus15000 0 15000 30000
Leve
l
minus5
0
5
10
15
20
25
30
35
40
Leve
l
Moment (kNmiddotm)
minus1200 minus800 minus400 0 400 800 1200
Shear (kN)
Option-1Option-2
Option-3Option-4
Option-1Option-2
Option-3Option-4
Figure 17 Moment and shear envelope in one typical column
minus20 minus10 00 10 20
Base
shea
r (kN
)
Top displacement (m)
Option-1Option-2
Option-3Option-4
300E + 04
200E + 04
100E + 04
000E + 00
minus100E + 04
minus200E + 04
minus300E + 04
Figure 18 Base shear versus top displacement relationship in firstmode load pattern
displacement is compared in Figure 18 It can be seen that thiscurve is flag shaped for Option-1 whereas it is bilinear pinch-ing type in Options-2ndash4There is no permanent deformationin controlled structure and flag shaped hysteresis behaviouris observed The same behaviour was observed during testconducted on a large-scale model of a concrete shear wallfrom the core of a high-rise building in the study of Adebar etal [27] The combination of low percentage of vertical rein-forcement and large axial compression force due to gravity
loads (axial force(concrete 28 days cylinder strength times grossarea ofwall)gt 01) caused the flexural cracks to closewhen thelateral load was removed In Options-2ndash4 small permanentdeformation (residual displacement) is observed This isbecause of the plastification of BRBs as well as transfer of themoment demand from shear wall to columns in the form ofaxial push-pull
8 Conclusions
(i) In this study different options of location of BRBsare investigated for a 40-story case study buildingThe locations of BRBs are identified based on theDBE elastic racking shear deformation and shear andbending moment demands in dominant 2nd and 3rdmodes NLRHA is then performed for seven sets ofspectrally matched target time histories and resultsare compared for different options
(ii) In all options shear force demands bending momentat mid height displacement demand racking sheardeformation demand and rotation demand in cou-pling beams are reduced by 10 45 45 45 and40 respectively in comparison to the controlledstructure
(iii) Rotational demand in the core wall at base level isreduced by 99 57 and 93 in Option-2 Option-3 and Option-4 respectively in comparison toOption-1Whereas energy dissipated by the core wallis reduced by around 250 in the corewall in compar-ison to the controlled structure Rotational demandand energy dissipation are measure of damage in thecore wall Thus damage can be significantly reducedby installation of BRBs
14 Shock and Vibration
(iv) All BRBs options are effective for bending momentreduction at mid height displacement and rackingshear deformation demands along the wall heightand rotation demand at the base of the wall and incoupling beams above the mid height of the build-ing However Option-4 in which BRBs are installedbetween peripheral columns and central corewall andcut in shear walls based on the maximum shear forceand bending moment leads to the highest reductionThis is because of the early yielding of the interiorbraces
(v) Thiswork is equally important for academia and prac-tising engineers especially those working in the fieldof performance based design of the high-rise build-ings in the commercial consultancy This will helpthem to locate BRBs at appropriate locations whiledesigning their buildings in an optimal way
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] International Conference of Building Officials Uniform Build-ing Code vol 2 International Conference of Building OfficialsWhittier Calif USA 1997
[2] J Maffei and N Yuen ldquoSeismic performance and designrequirements for high rise buildingsrdquo Structural Magazine pp28ndash32 2007
[3] J P Moehle ldquoPerformance-based seismic design of tall build-ings in the USrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[4] CEN EC8 Design of Structures for Earthquake ResistanceEuropean Committee for Standardization Brussels Belgium2004
[5] NZS 3101 Part 12006 Concrete Structures Standards NewZealand Standards New Zealand Wellington New Zealand2006
[6] T Paulay and M J N Priestley Seismic Design of ReinforcedConcrete and Masonry Buildings Wiley Hoboken NJ USA1992
[7] M Panagiotou J I Restrepo and J P Conte ldquoShake table test ofa 7-story full scale reinforced concrete structural wall buildingslice phase I rectangular wallrdquo Report SSRP 07-07 Departmentof Structural Engineering University of California San DiegoSan Diego Calif USA 2007
[8] Canadian Standard Association CSA Standard A233-04Design of Concrete Structures Canadian Standard AssociationRexdale Canada 2005
[9] R Klemencic J A Fry J D Hooper and B G MorgenldquoPerformance-based design of ductile concrete core wall build-ingsmdashissues to consider before detailed analysisrdquoTheStructuralDesign of Tall and Special Buildings vol 16 no 5 pp 599ndash6142007
[10] R Klemencic ldquoPerformance based seismic designmdashrisingrdquoStructural Magazine 2008 httpwwwstructuremagorgwp-contentuploads201408C-StructuralPractices-Klemencic-June081pdf
[11] A Zekioglu M Willford L Jin and M Melek ldquoCase studyusing the Los Angeles tall buildings structural design councilguidelines 40-storey concrete core wall buildingrdquo StructuralDesign of Tall and Special Buildings vol 16 no 5 pp 583ndash5972007
[12] B R Rad and P Adebar ldquoDynamic shear amplification inhigh-rise concrete walls effect of multiple flexural hinges andshear crackingrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[13] M Panagiotou and J I Restrepo ldquoDual-plastic hinge designconcept for reducing higher-mode effects on high-rise can-tilever wall buildingsrdquo Earthquake Engineering and StructuralDynamics vol 38 no 12 pp 1359ndash1380 2009
[14] M Ahmed and P Warnitchai ldquoReduction of inelastic seismicdemands by inducing plastic hinges at effective locationsrdquoin Proceedings of the 3rd Asian Conference on EarthquakeEngineering (ACEE rsquo10) Bangkok Thailand December 2010
[15] A Munir and P Warnitchai ldquoThe cause of unproportion-ately large higher mode contributions in the inelastic seismicresponses of high-rise core-wall buildingsrdquo Earthquake Engi-neering amp Structural Dynamics vol 41 no 15 pp 2195ndash22142012
[16] A Munir and P Warnitchai ldquoOptimal reduction of inelasticseismic demands in high-rise reinforced concrete core wallbuildings using energy-dissipating devicesrdquo Structural Design ofTall and Special Buildings vol 22 no 7 pp 543ndash568 2013
[17] M C Constantinou and M D Symans ldquoExperimental andanalytical investigation of seismic response of structures withsupplemental fluid viscous dampersrdquo NCEER Reports 92-0032State University of New York at Buffalo Buffalo NY USA 1992
[18] A SWhittaker V V Bertero C LThompson and L J AlonsoldquoSeismic testing of steel plate energy dissipation devicesrdquoEarthquake Spectra vol 7 no 4 pp 563ndash604 1991
[19] G W Housner L A Bergman T K Caughey et al ldquoStruc-tural control past present and futurerdquo Journal of EngineeringMechanics vol 123 no 9 pp 897ndash971 1997
[20] M D Symans F A Charney A S Whittaker et al ldquoEnergydissipation systems for seismic applications current practiceand recent developmentsrdquo Journal of Structural Engineering vol134 no 1 pp 3ndash21 2008
[21] C J Black N Makris and I D Aiken ldquoComponent testingseismic evaluation and characterization of buckling-restrainedbracesrdquo Journal of Structural Engineering vol 130 no 6 pp880ndash894 2004
[22] S Keten A performance based approach for seismic designwith hysteretic dampers [MS thesis] Massachusetts Institute ofTechnology (MIT) 2006 httpdspacemitedubitstreamhan-dle172113459571252112-MITpdfsequence=2
[23] N Anwar J A Sy T H Aung and D Rayamajhi ldquoFirstapplication of buckling restraint brace system in Philippines ina 50-story building with ductile core wall and PT slab systemrdquoin Proceedings of the 9th International Conference on UrbanEarthquake Engineering and the 4th Asia Conference on Earth-quake Engineering Tokyo Institute of Technology Tokyo JapanMarch 2012
[24] Computers and Structures Inc ETABS Extended 3D Analysis ofBuilding Systems Software Nonlinear Version 900 Computersand Structures Inc Berkeley Calif USA 2005
[25] Computers and Structures Perform 3D Nonlinear Analysis andPerformance Assessment for 3D Structures User Guide Version 4Computers and Structures Berkeley Calif USA 2006
Shock and Vibration 15
[26] J W Wallace and J P Moehle ldquoDuctility and detailing require-ments of bearing wall buildingsrdquo Journal of Structural Engineer-ing vol 118 no 6 pp 1625ndash1644 1992
[27] P Adebar A M M Ibrahim and M Bryson ldquoTest of high-risecore wall effective stiffness for seismic analysisrdquo ACI StructuralJournal vol 104 no 5 pp 549ndash559 2007
[28] FEMA ldquoPrestandard and commentary for the seismic rehabil-itation of buildingsrdquo FEMA 356 Federal Emergency Manage-ment Agency Washington DC USA 2000
[29] LATBDSC An Alternative Procedure for Seismic Analysis andDesign of Tall Buildings Located in Los Angeles Region A Con-sensus Document Los Angeles Tall Buildings and StructuralDesign Council 2008
[30] PEERNGAData Base Pacific Earthquake Engineering Research(PEER) University of California Berkeley Calif USA 2005httppeerberkeleyedunga
[31] COSMOS Data Base ldquoConsortium of organization for strong-motion observation systemsrdquo Tech Rep University of Cali-fornia Berkeley Calif USA 1999ndash2007 httpwwwcosmos-eqorgscriptsdefaultplx
[32] K Lilhanand and W S Tseng ldquoDevelopment and applicationof realistic earthquake time histories compatible with multipledamping design spectrardquo in Proceedings of the 9th World Con-ference on Earthquake Engineering Tokyo Japan August 1988
[33] J Hancock J Watson-Lamprey N A Abrahamson et al ldquoAnimproved method of matching response spectra of recordedearthquake ground motion using waveletsrdquo Journal of Earth-quake Engineering vol 10 no 1 pp 67ndash89 2006
[34] J B Mander M J N Priestley and R Park ldquoTheoreticalstress-strain model for confined concreterdquo Journal of StructuralEngineering New York vol 114 no 8 pp 1804ndash1826 1988
[35] CTBUH Seismic Working Group CTBUH Recommendationsfor the Seismic Design of High-Rise Buildings A ConsensusDocument 2008
[36] N Satake K-I Suda T Arakawa A Sasaki and Y TamuraldquoDamping evaluation using full-scale data of buildings inJapanrdquo Journal of Structural Engineering vol 129 no 4 pp 470ndash477 2003
[37] Q Xie ldquoState of the art of buckling-restrained braces in AsiardquoJournal of Constructional Steel Research vol 61 no 6 pp 727ndash748 2005
[38] P Clark K Kasai I Aiken E Ko and I Kimura ldquoDesign proce-dures for buildings incorporating hysteretic energy dissipatingdevicesrdquo in Proceedings of the 68th Annual Convention Struc-tural Engineers Association of California Santa Barbara CalifUSA October 1999
[39] D Vafaei and R Eskandari ldquoSeismic response of mega buck-ling-restrained braces subjected to fling-step and forward-directivity near-fault ground motionsrdquo Structural Design of Talland Special Buildings vol 24 no 9 pp 672ndash686 2015
[40] L Di Sarno and A S Elnashai ldquoBracing systems for seismicretrofitting of steel framesrdquo Journal of Constructional SteelResearch vol 65 no 2 pp 452ndash465 2009
[41] A Dutta and R O Hamburger ldquoCase study of A 40-Storeybuckling-restrained braced frame building located in LosAnge-lesrdquo The Structural Design of Tall and Special Buildings vol 19no 1-2 pp 77ndash93 2010
[42] Rutherford amp Chekene ldquoPerform nonlinear component mod-elling of star seismic powercat BRBsrdquo Report to Star SeismicLLC Star Seismic LLC 2011
[43] P Dusicka A M Itani and I G Buckle ldquoCyclic response ofplate steels under large inelastic strainsrdquo Journal of Construc-tional Steel Research vol 63 no 2 pp 156ndash164 2007
[44] S A Razavi M E Shemshadian S R Mirghaderi and SAhlehagh ldquoSeismic design of buckling restrained braced frameswith reduced core lengthrdquo in Proceedings of the The StructuralEngineers World Congress Cernobbio Italy 2011
[45] S A Razavi S R Mirghaderi A Hosseini and M EShemshadian ldquoReduced length buckling restrained brace usingsteel plates as restraining segmentrdquo in Proceedings of the 15thWorld Conference on Earthquake Engineering Lisboa PurtagalSeptember 2012
[46] M E Shemshadian S A Razavi S R Mirghaderi A Hosseiniand M K Mohammadi ldquoThe advantages of reducing thelength of yielding segment in seismic performance of bucklingrestrained braced framesrdquo inProceedings of the 6th InternationalConference of Seismology and Earthquake Engineering TehranIran 2011
[47] N Ma B Wu J Zhao H Li J Ou andW Yang ldquoFull scale testof all-steel buckling restrained bracesrdquo in Proceedings of the 14thWorld Conference on Earthquake Engineering Beijing ChinaOctober 2008
[48] L Di Sarno and G Manfredi ldquoSeismic retrofitting of existingRC frames with buckling restrained bracesrdquo in Proceedings ofthe Improving the Seismic Performance of Existing Buildingsand Other Structures pp 741ndash752 San Francisco Calif USADecember 2009
[49] S Ahlehagh Improvement of the special concentrically bracedsteel frames behaviour by employing balanced braces [MSthesis] University of Tehran Tehran Iran 2008
[50] R Tremblay P Bolduc R Neville and R DeVall ldquoSeismic test-ing and performance of buckling-restrained bracing systemsrdquoCanadian Journal of Civil Engineering vol 33 no 2 pp 183ndash1982006
Several approaches were proposed to reduce thesedemands One approach is to allow the wall to yield at anylocation along its height This approach is referred to asDuctile Wall (DW) approach and was proposed by [12] Thisapproach is uneconomical due to stringent ductile detailingrequirements all along the wall height Furthermore thesebuildings may not be economically repairable due to spreadof damage in a seismic event The second approach is DualPlastic Hinge (DPH) approach in which one hinge is allowedat mid height in addition to the plastic hinge at the base [13]This approach is effective only for reduction of 2nd modebending moment demand at mid height of the wall Anotherapproach in which plastic hinges were allowed at severaleffective locations was proposed by [14ndash16]
However in all the above-mentioned approaches damageis allowed in main structural components such as shearwalls and coupling beams To avoid this another strategywhich incorporates energy dissipating devices (EDDs) in thestructural system to reduce the inelastic energy dissipationdemand on the framing system [17 18] has been introducedIn this strategy the structural components may remain elasticor suffer less damage during an earthquake the structural andnonstructural damage may be considerably reduced Thesedevices were incorporated in a number of new buildings andwere used to retrofit existing buildings to reduce the windand seismic induced responses [19 20] Buckling restrainedbraces (BRBs) are one of the proven choices as EDDs forreducing seismic response reduction In Japan BRBs havebeen used successfully for many projects in retrofitting ofthe existing buildings as well as design of new buildingsHowever in the United States (US) their use is reported in 30buildings including retrofitting of the existing buildings andnew construction [21 22] (Black et al 2004 Keten 2006)
Their recent use in high-rise buildings is reported in a 60-story One Rincon Hill Building in San Francisco [10] and 50-story tall ductile core wall building in Philippines [23]
In this study effect of BRBs locations on 40-story high-rise RC core wall case study building is studied in detailusing Nonlinear Response History Analysis (NLRHA) BRBshave been placed at critical locations in cut in shear wallsand between peripheral columns and shear wallsThe criticallocations are identified based on DBE elastic racking sheardeformation demands and force demands The comparisonbetween different options in terms of force (shear force andbendingmoment) deformation (displacement racking sheardeformation and plastic hinge rotation in wall) and energydemands has been shown
2 The Case Study Building andElastic Modal Demands
21 Description of the Case Study Building The building istaken fromprevious research studies [9ndash11 14ndash16]The typicalfloor plan of the building and 3Dmodel are shown in Figure 1This is a 40-story residential tower above the ground withthree levels of below-grade parking The typical story heightis 3m and a lobby-level height is 6m Thus the total heightof building above ground is 120mThe building is supportedby a thick foundation slab to transfer load on a firm groundThe soil condition beneath and surrounding the building isrepresented by stiff clay soil This is equivalent to the soiltype SD in the UBC-97 [1] The structural components of thebuilding are comprised of a central RC core wall thickness(750mmTH up to Level 20 and 600mm thick form Levels 21to 40) 14 peripheral columns (900mm times 900mmup to Level
Shock and Vibration 3
0
05
1
15
2
25
3
35
Response spectra of scaled ground motionsSH-PR-360 times 30HM-H-090 times 40LP-HSP-000 times 15CM-EUR-090 times 40Hon-MGH-EW times 40Chichi-Taipei-090 times 60Imp-Ch-012 times 40
DBE spectrum (UBC-97 zone 4 SD)MCE spectrum (DBE spectrum times 15)
0
05
1
15
2
0 1 2 3 4 5 6 7 8 9 10Natural period (s)
0 1 2 3 4 5 6 7 8 9 10Natural period (s)
Spec
tral
acc
(g)
Spec
tral
acc
(g)
Target spectra
Figure 2 Comparison of the matched spectra of the groundmotions with DBE and MCE spectra
20 and 600mm times 600mm from Level 21 to Level 40) and200mm-thick posttensioned concrete flat slabs resting on theperipheral columns and the central core wall There are dooropenings in the wallThese openings are covered by couplingbeams The size of coupling beams is 600mm times 1500mmabove lobby level and 750mmtimes 800mm fromLevel 3 to Level20 whereas it is 600mm times 700mm from Levels 21 to 40Thecompressive strength of concrete for columns and walls is setto 55MPa up to Level 20 and 42MPa from Level 20 to theroof The reinforcing bars are Grade-60 steel with specifiedyield strength of 420MPa The central core wall forms thelateral load resisting system whereas posttensioned slabsand peripheral columns shall mainly form the gravity loadresisting system The gravity load includes self-weight of thestructure dead loads of 192 kNm2 and live loads of 24 kNm2
22 DBEElasticModal Demands byModal Response SpectrumAnalysis The modal response spectrum analysis (MRSA) ofthe building is performed using UBC-97 [1] design basisresponse spectrum for seismic zone-4 and soil type SD for5 damping in the single mode of vibration The responsespectrum is shown in Figure 2 The building is analysed in
the119883-direction only for brevity and considered sufficient forthe purpose of this study The commercial software ETABS[24] is used for MRSA procedure First six modes are foundto be sufficient for 90 mass participation in the MRSAHowever results show that both shear and moment demandsare mainly dominated by first four modes The combineddemands are obtained by combining individual modaldemands using CQC method
DBE elastic demands in the core wall in first four domi-nantmodes as well as their combination are shown in Figures3(a) 3(b) 3(c) and 3(d) respectively Both shear andmomentdemands are dominated by 1st 2nd and 3rd mode whereasdeformation demands are dominated by the 1st mode onlyThese demands shall be used for preparation of model forNonlinear Response History Analysis and to find the criticallocations of the BRBsThe story racking deformation angle isthe shear deformation of the panel between wall and periph-eral columnsThis is equal to the conventional story drift ratiosubtracted by the floor inclination angle measured clockwisefrom a horizontal plane
3 Description of Model forNonlinear Response History Analysis andSelection of Ground Motions
The nonlinear model is implemented in Commercial Soft-ware Perform-3D [25] The core wall is modelled using 22one-story high (3m) inelastic shear wall elements at theplastic hinge location at the base Each shear wall element wascomprised of 8 concrete and 8 steel fibres at the plastic hingelocations whereas the wall at other locations is modelled asthe 22 linear elastic shear wall elements The previous studies[26 27] show that plastic hinge length of the high-rise wallmay be taken as 12 to 23 times wall length (Lw) The lengthof the wall in this case is 10m Therefore plastic hinges wereallowed over two-story height (6m) which is approximately23 Lw However one-story high inelastic shear wall elementswere used over the plastic hinge length based on section68222 of FEMA-356 [28] which mentions that plastichinge length should be smaller than one-story height or Lw2
The flexural strength at the plastic hinge location shouldbe as low as possible to allow early yielding of the wall but atthe same time plastic hinge rotation as well as related defor-mation demands such as story drift and racking shear defor-mation should bewithin permissible limits In this study flex-ural strength is based on the DBE design moment demandsdetermined by code based procedure of UBC-97 [1] Theseare larger than the values obtained either (a) by dividing thecombined elastic demands by appropriate response modifi-cation factor ldquo119877rdquo of 55 or (b) by dividing ldquo119877rdquo factor requiredto satisfy the requirement of 90 of the base shear obtainedfrom static analysis procedure There are mainly two reasonsfor setting flexural strength in this way (1) this is based on thestandard code based design such as UBC-97 [1] (2) moderncode such as LATBDC-2008 [29] recommend capacity designas a first step of the performance based design and designersare using the code based design as the initial step and later
4 Shock and Vibration
minus5
0
5
10
15
20
25
30
35
40
0 3 6
Leve
l num
ber
CombinedMode-1Mode-2
Mode-3Mode-4
Moment (kNmiddotm times 106)
(a)
minus5
0
5
10
15
20
25
30
35
40
Leve
l num
ber
0 50 100
CombinedMode-1Mode-2
Mode-3Mode-4
Shear (kN times 103)
(b)
minus5
0
5
10
15
20
25
30
35
40
0 025 05 075 1
Leve
l
Displacement (m)
CombinedMode-1Mode-2
Mode-3Mode-4
(c)
minus5
0
5
10
15
20
25
30
35
40
Leve
l
0 001Racking shear deformation ratio
002
CombinedMode-1Mode-2
Mode-3Mode-4
(d)
Figure 3 DBE elasticmodal and total seismic demands (a)Moment demands (b) shear demands (c) displacement demands and (d) rackingshear deformation demands
confirm the performance at MCE level by the NLRHAprocedure
Plastic hinges are also induced at both ends of cou-pling beams The characteristics of the plastic hinges aredetermined by beam cross section properties and flexural
reinforcement worked out based on the design demands andassumed plastic hinge length of 05 times the depth of thebeam The remaining portion of the coupling beam is mod-elled as elastic beam element A trilinear moment-curvaturerelationship without stiffness and strength degradation is
Shock and Vibration 5
Stre
ss
Strain
Stre
ss
Strain
Unloading and reloading arethe same in case of tension
Steel material Concrete material
Mander envelopePerform-3D UnloadingReloading
f998400cc
Eo
EoEo
dcEo
120585998400cc120585998400c120585cu
ft
fu
fy
Park envelopePerform-3D Cyclic
120585y 120585sh 120585u
fy rebar yield stressfu rebar ultimate stress capacity120585y rebar yield strain120585sh strain in rebar at the onset of strain hardening120585y rebar ultimate strain capacityEo modulus of elasticiy
f998400c compressive strength of unconfined concrete
f998400cc compressive strength of confined concrete
120585998400c concrete strain atf998400c
120585998400cc concrete strain atf998400cc
120585cu ultimate strain capacity for confined concreteEo tangent modulus of elasticitydc energy dissipation factor for the reloading stiffnessft tensile strength of concrete = 75radicf998400
c (f998400c is in psi)
Figure 4 Nonlinear Park Steel and Manderrsquos concrete model
used for modelling plastic hinges at the ends of couplingbeams All slabs and columns aremodelled by elastic slab andcolumn elements of the Perform-3D respectively
Seven set of ground motions are selected from PEER[30] and COSMOS [31] data bases The ground motionsinclude both short distance moderate and long distancelarge magnitude earthquake The selected ground motionsare first roughly scaled up or down by a constant factor toapproximately match the target MCE spectrum The roughlyscaled ground motions are then matched to the MCE targetspectrum by using time domain spectral matching techniqueof [32] The software RSP match [33] is used for this purposeThe target spectrum and spectra of seven spectrally matchedtime history used in this study are shown in Figure 2 Non-linearmaterial models similar to those proposed by [34] wereassigned for rebarrsquos and concrete material respectively asshown in Figure 4 The modal damping is set as per recom-mendations of [35] CTBUH (2008) and [36]
4 Analysis of Structure without BRBs
The controlled structure described in Section 3 is analysedfor seven sets of ground motions The shear and momentdemands obtained are shown in Figure 5 These results showthat base shear demand is about 15 of the total building
weight Similarly moment demand is also very high at midheight However at the base the moment demand is clippedto the flexural strength of plastic hinge If the wall is designedfor mid height moment to remain elastic and hence nodamage there shall be reinforcement congestion On theother hand if plastic hinge is allowed at mid height the corewall shall be subjected to high rotational demands and hencedamage near themid height of thewall in addition to the baseTo reduce damage at the base of the wall as well as reducemid height moment to avoid reinforcement congestion analternative strategy using different arrangements of buck-ling restrained braces (energy dissipating devices) has beenevolved in the next section (Options-2ndash4) and results arecompared with the controlled structure (Option-1)
5 Buckling Restrained Braces Evolvement ofStrategies for Efficient Locations Their Sizeand Modelling
51 Buckling Restrained Brace An ordinary brace exhibitsunstable hysteretic behaviour due to buckling in compres-sion hence it cannot dissipate much energy To avoid com-pression buckling and to achieve more energy dissipationanother brace known as buckling restrained brace (BRB) hasbeen introduced This type of brace exhibits stable hysteric
6 Shock and Vibration
0 40 80 120
Mean MCE demands Mean MCE demands
0 1 2 3minus5
0
5
10
15
20
25
30
35
40
Leve
l num
ber
minus5
0
5
10
15
20
25
30
35
40
Leve
l num
ber
Shear (kN times 103) Moment (kNmiddotm times 106)
Figure 5 Inelastic MCE shear and moment demands in the controlled structure
Encasing mortar
Yielding steel core
Steel tube
Unbonding materialbetween steel core
and mortar
Figure 6 Typical BRB
behaviour because its compression buckling is avoided due toencasing by an outer steel tubeThemain brace and outer tubeare separated by bonding material in order to accommodatethe lateral expansion due to its compression yielding [37] Atypical BRB is shown in Figure 6 [38]
52 Location of Buckling Restrained Braces BRBs have beeninstalled at several critical locations based on the results ofelastic modal decomposition analysis in dominant modessuch as 1st 2nd and 3rd modes and results are comparedwith controlled structure described in Section 4 (Option-1)In second option (Option-2) the BRBs have been installed
at bays 2 3 and 4 between peripheral columns and centralcore wall based on the maximum racking shear deformationdemands in 2nd and 3rd modes This arrangement is shownin Figure 7 In third option small size BRBs have also beeninstalled at bays 2 and 4 in cut in central core wall at the max-imum moment demands in 2nd and 3rd modes These BRBsare in addition to the BRBs in Option-2 This arrangementis shown in Figure 8 In final and fourth option (Option-4)BRBs have been installed in cut in central core wall at bays 2and 4 at the location of maximum shear force in 2nd and 3rdmodes in addition to the BRBs in Option-2 This is shownin Figure 9 It may be noted that the locations of BRBs in
Shock and Vibration 7
0
5
10
15
20
25
30
35
40
0
000
1
000
2
000
3
000
4
000
5
Leve
l
Racking shear deformation ratioMode-2Mode-3
Mode-4
Figure 7 Arrangement of the BRBs at locations of maximum racking shear deformation in exterior panels (Option-2)
0
5
10
15
20
25
30
35
40
0 1 2 3
Leve
l
0
5
10
15
20
25
30
35
40
Leve
l
Mode-2Mode-3
Mode-4 Mode-2Mode-3
Mode-4
Moment (kNmiddotm times 106)
0
000
1
000
2
000
3
000
4
000
5
Racking shear deformation ratio
Figure 8 Arrangement of the exterior BRBs at locations of maximum DBE elastic racking shear deformation in 2nd and 3rd mode andinterior BRBs at locations of maximum DBE elastic moment demands in 2nd and 3rd mode (Option-3)
8 Shock and Vibration
0
5
10
15
20
25
30
35
40Le
vel
0
5
10
15
20
25
30
35
40
0 50 100
Leve
l num
ber
Shear (kN times 103)
Mode-2Mode-3
Mode-4 Mode-2Mode-3
Mode-4
0
000
1
000
2
000
3
000
4
000
5
Racking shear deformation ratio
Figure 9 Arrangement of the exterior BRBs at locations of maximum DBE elastic racking shear deformation in 2nd and 3rd mode andinterior BRBs at locations of maximum DBE elastic shear demands in 2nd and 3rd mode (Option-3)
Option-1 Option-2 andOption-3 are also suitable for mode-1
The BRBs dissipate energy through axial tension andcompression To achieve maximum energy dissipation theBRBs should be placed at the proper locations and anglesEach BRB has been placed at an angle of approximately1205874 covering almost three stories for exterior brace and twostories for brace in cut in core wall These V-shaped BRBsconfigurations resemble the BRBs configuration used inmegabraced frames steel buildings reported in the previous studies[39ndash41] BRBs shall cross the slabs through purposely builtopenings provided in the slabs A horizontal drag elementis used from point where BRB connects to the column tothe central core wall to take care of the horizontal forcecomponent of the BRB axial force at column connection
53 Size of Buckling Restrained Braces Sizes of the BRBs havebeen selected by hit and trial using more rigorous nonlineartime history analyses (NLTHAs) using displacement-baseddesign approach Their size should neither be too large tobe uneconomical nor be too small to be ineffective The 119883-section of the braces between peripheral columns and centralcore wall is selected as 7500mm2 whereas it is 3750mm2for braces in cuts in core wall The buckling restrained bracesmanufactured by star seismic with normal yield strength of280MPa are used for braces between peripheral columnsand central core wall [42] However the low yield point-100(LYP100) steel core manufactured by Nippon Steel Corpora-tion Japan with specified yield strength of 100MPa is used
f
0DXDU
FY
FUO
FUH
KF
KO
Figure 10 Trilinear curve for BRBs
for braces in cut elements [22]The lowyield point steel bracesare used in cut in core wall to mainly achieve more energydissipation through the early yielding of the brace [43]
54 Modelling of Buckling Restrained Braces A BRB consistsof three components that is central yielding core brace endsmember connecting the central brace with the pin connec-tion and pin connection between brace and main structuralmembers The length of the exterior core brace is 45mwhereas length of the core brace in cut of core wall is 18mThese lengths are in the optimum range of 02ndash04 times thetotal length of the brace Several advantages such as simple
Shock and Vibration 9
minus4000
minus3000
minus2000
minus1000
0
1000
2000
3000
4000A
xial
forc
e ( k
N)
Axial def (m)
10E minus 0150E minus 0200E + 00minus50E minus 02
(a)
minus500
minus400
minus300
minus200
minus100
0
100
200
300
400
500
Axi
al fo
rce (
kN
)
Axial def (m)
20E
minus03
10E
minus03
00E
+00
minus30E
minus03
minus20E
minus03
minus10E
minus03
(b)
Figure 11 Typical cyclic response of BRBs obtained from the analysis (a) Exterior brace (b) interior brace
replacement lesser weight concrete elimination economyand easy erection process are associated with reduced lengthof the core brace [44ndash50] BRB has been modelled using theBRB compound component of the Perform-3D Such mem-ber is composed of three components that is (1) a BRB basiccomponent for main yielding brace (2) an elastic bar basiccomponent for member connecting brace with gusset plateand (3) a stiff end zone which accounts for the gusset platesand so forth at both ends of the member
The positive side (tension) of the trilinear curve to definethe force-deformation of the BRBs is shown in Figure 10 Itcan be seen that after yielding there are two lines such asbottom and top line The bottom line is used to simulate firstcyclic load and the top line is used to simulate full strainhardening The same behavior has been observed in testslike the hysteresis loop which can progressively grow in sizeThis is sometimes referred to as ldquoisotropic hardeningrdquo Thisleads to the component increase in strength under cyclic loadThe negative side of the curve shows a little variation due todifference in the values of compression and tensions FY FUO(FUO (T) = 105 FY FUO (C) = 104 FY) and FUH (FUO(T) = 134 FY FUO (C) = 151 FY) are yield strength strengthat first loading cycle and strength of the core brace afterfull hardening respectively DU (DU (T) = 07 DU (C) =07) is the deformation at FUO and DX (DX (T) = 004 LYCDX (C) = 004 LYC) is the maximum deformation of thebrace LYC is the length of the yielding core KO is theInitial stiffness of the core brace and KF (= 002KO) is theslope of third line [42] The strain hardening properties suchas deformation at FUO-FUH average are taken equal to 2times (LYC180) and deformation at FUH is taken as 35times (LYC180) The typical force-deformation relationshipfor exterior (between peripheral columns and core wall) andinterior BRB (in cut in core wall) obtained from NLRHAanalysis for a particular ground motion is shown in Figures11(a) and 11(b) respectivelyThese figures show that hysteresisloop is similar to the reported Clark et al 1999 [38] provingthat performing BRB element can capture the behaviour
appropriately The size of the elastic bar element is selectedsuch that it can safely carry maximum axial force in brace inelastic range to conform to the capacity design approach Stiffend zone is few times stiffer than the elastic bar element
6 Comparison of the Responses in DifferentOptions and Discussion on the Results
NLRHA is performed using seven spectrally matched timehistories Different response quantities such as displacementplastic hinge rotations in coupling beams and core wall sheardeformation angle (story racking shear deformation) bend-ing moment shear force and energy demands are obtainedfrom this analysisThe plastic rotations are calculated bymul-tiplying the average curvature of the wall at mid height withthe plastic hinge length The mean value of different quan-tities obtained from seven ground motions are shown anddiscussed in following paragraphs
Shear demands obtained from four options are shownin Figure 12(a) Shear demand pattern and magnitude aresimilar in all options Moment demands obtained from fouroptions are shown in Figure 12(b) The moment demand atthe base is similar in all four options because this is clippedto the flexural strength of the plastic hinge at the base of thewall However it is reduced along the wall height by 30 35and 40 in Option-2 Option-3 and Option-4 respectivelyin comparison to that in 1st optionThe reduction inmomentdemand is significant in all options This will help to avoidreinforcement congestion in the wall near mid height
Displacement demands obtained from four options areshown in Figure 13(a) Displacement demand pattern is simi-lar for all options However displacement demand is reducedalong thewall height by 40 40 and 60 inOption-2 Option-3 and Option-4 respectively in comparison to that in 1stoption Racking shear deformation demands obtained fromfour options are shown in Figure 13(b) The racking sheardeformation demand patterns are similar for all four optionsHowever racking shear deformation demands are reduced
10 Shock and Vibration
minus5
0
5
10
15
20
25
30
35
40
0 50000 100000 150000
Leve
l
Shear force (kN)
Option-1Option-2
Option-3Option-4
(a)
minus5
0
5
10
15
20
25
30
35
40
Leve
l
0 1 2 3
Option-1Option-2
Option-3Option-4
Bending moment (kNmiddotm times 106)
(b)
Figure 12 MCE inelastic shear and moment demands in different options (a) Shear (b) moment
0 05 1 15 2 25Displacement (m)minus5
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(a)
0 001 002 003 004Racking shear deformation ratio
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(b)
Figure 13 MCE inelastic displacement and racking deformation demands in different options (a) Displacement (b) racking sheardeformation angle
along the wall height by 40 40 and 65 in Option-2Option-3 and Option-4 respectively in comparison to thatin 1st option This is significant reduction Racking sheardeformations of 0036 in the controlled structures are reducedto 0023 which is well within the limit of 003 set by [29]LATBSDC 2008 for the MCE level earthquake
Rotational demands in the core wall at the base level aswell as in coupling beams along the height are shown in Fig-ures 14(a) and 14(b) respectivelyThe rotation demand in thewall is calculated by multiplying the average curvature at themid height of the inelastic wall element by height of the wallThe comparison shows that themaximum rotational demand
at the base of the wall is reduced by 99 57 and 93 inOption-2Option-3 andOption-4 respectively in comparison to thatin 1st option This is strong indication that damage at thebase of the wall shall be reduced to half and consequentlyextent of repair shall be small and hence cheap in case ofsevere MCE events such as DBE and MCE level earthquakeThe rotational demands in coupling beams are reduced by52 40 and 35 respectively above the half height level forOption-2 Option-3 and Option-4 respectively in compar-ison to 1st option However rotation demand remained thesame in the lower half portion of the building for all options
Energy dissipated by core wall coupling beams andbuckling restrained braces have been compared in Figures15(a)ndash15(d) respectively for Option-1 Option-2 Option-3 and Option-4 respectively This is energy dissipated inpercentage of the total energy demand in the structure Thetotal energy demand is sum of the kinetic energy elasticstrain energy energy dissipated by elastic modal dampingand energy dissipation by damage in structural elements suchas core wall coupling beams and BRBs About 83 9292 and 90 energy have been dissipated by elastic modaland inelastic damping in Option-1 to Option-4 respectivelyThe energy dissipation by modal elastic damping to the totalenergy demands is 50 37 35 and 33 respectively inOption-1 to Option-4 respectivelyThe energy dissipation bycore wall at the base to the total energy demands is 22 66 and 6 inOption-1 to Option-4 respectivelyThe energydissipation by coupling beams to the total energy demands isapproximately 10 4 5 and 6 in Option-1 to Option-4 respectively The energy dissipation by BRBs to the total
energy demands is 0 45 45 and 45 respectively inOption-1 to Option-4
7 Effects of BRBs on Axial Loads Shearand Moment of Columns and PermanentDeformation due to BRBs Plastification
Effects of BRBs on axial loads of columns and permanentdeformation due to BRBs plastification have been discussedin this section The axial load envelope in a typical columnfor Options-1ndash4 is shown in the Figure 16 The magnitude ofaxial load is same for Options-2ndash4 (with BRBs) and is twicethan that in Option-1 (controlled structure) This is due tothe outrigger effect created by the connection of columnsand core wall through BRBs Some core wall moment hasbeen resisted by the development of axial push-pull in thecolumns Furthermore the shape of the axial load envelopeis smooth in case of Option-1 whereas it is jagged at thelocations of the BRBs forOptions-2ndash4Themoment envelopeand shear envelope for one typical column are shown inFigures 17(a) and 17(b) respectively It shows that momentand shear have been reduced at the ground level in Options-2ndash4 in comparison to Option-1 whereas these remain almostthe same at upper portions The extra moment and shearat the ground level in Options-1ndash4 is due to the transfer ofmoment and shear to the columns when core wall yields
To better understand the permanent deformation in thestructure due to BRBs plastification cyclic pushover analysisin firstmode is performedusing target displacement obtainedfrom NLTHA for all cases The cyclic base shear versus top
12 Shock and Vibration
Option-1
0
20
40
60
80
100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 53478kNmiddotm
(a)
Option-2
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 73328kNmiddotm
(b)
Option-3
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80 90
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 71449kNmiddotm
(c)
Option-4
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 69558kNmiddotm
(d)
Figure 15 Inelastic energy demands in structural components (a) to (d) For Option-1 to Option-4 respectively
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus20000 minus10000 0
Leve
l
Axial load (kN)
Option-1Option-2
Option-3Option-4
Figure 16 Axial load envelope in one typical column
Shock and Vibration 13
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus15000 0 15000 30000
Leve
l
minus5
0
5
10
15
20
25
30
35
40
Leve
l
Moment (kNmiddotm)
minus1200 minus800 minus400 0 400 800 1200
Shear (kN)
Option-1Option-2
Option-3Option-4
Option-1Option-2
Option-3Option-4
Figure 17 Moment and shear envelope in one typical column
minus20 minus10 00 10 20
Base
shea
r (kN
)
Top displacement (m)
Option-1Option-2
Option-3Option-4
300E + 04
200E + 04
100E + 04
000E + 00
minus100E + 04
minus200E + 04
minus300E + 04
Figure 18 Base shear versus top displacement relationship in firstmode load pattern
displacement is compared in Figure 18 It can be seen that thiscurve is flag shaped for Option-1 whereas it is bilinear pinch-ing type in Options-2ndash4There is no permanent deformationin controlled structure and flag shaped hysteresis behaviouris observed The same behaviour was observed during testconducted on a large-scale model of a concrete shear wallfrom the core of a high-rise building in the study of Adebar etal [27] The combination of low percentage of vertical rein-forcement and large axial compression force due to gravity
loads (axial force(concrete 28 days cylinder strength times grossarea ofwall)gt 01) caused the flexural cracks to closewhen thelateral load was removed In Options-2ndash4 small permanentdeformation (residual displacement) is observed This isbecause of the plastification of BRBs as well as transfer of themoment demand from shear wall to columns in the form ofaxial push-pull
8 Conclusions
(i) In this study different options of location of BRBsare investigated for a 40-story case study buildingThe locations of BRBs are identified based on theDBE elastic racking shear deformation and shear andbending moment demands in dominant 2nd and 3rdmodes NLRHA is then performed for seven sets ofspectrally matched target time histories and resultsare compared for different options
(ii) In all options shear force demands bending momentat mid height displacement demand racking sheardeformation demand and rotation demand in cou-pling beams are reduced by 10 45 45 45 and40 respectively in comparison to the controlledstructure
(iii) Rotational demand in the core wall at base level isreduced by 99 57 and 93 in Option-2 Option-3 and Option-4 respectively in comparison toOption-1Whereas energy dissipated by the core wallis reduced by around 250 in the corewall in compar-ison to the controlled structure Rotational demandand energy dissipation are measure of damage in thecore wall Thus damage can be significantly reducedby installation of BRBs
14 Shock and Vibration
(iv) All BRBs options are effective for bending momentreduction at mid height displacement and rackingshear deformation demands along the wall heightand rotation demand at the base of the wall and incoupling beams above the mid height of the build-ing However Option-4 in which BRBs are installedbetween peripheral columns and central corewall andcut in shear walls based on the maximum shear forceand bending moment leads to the highest reductionThis is because of the early yielding of the interiorbraces
(v) Thiswork is equally important for academia and prac-tising engineers especially those working in the fieldof performance based design of the high-rise build-ings in the commercial consultancy This will helpthem to locate BRBs at appropriate locations whiledesigning their buildings in an optimal way
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] International Conference of Building Officials Uniform Build-ing Code vol 2 International Conference of Building OfficialsWhittier Calif USA 1997
[2] J Maffei and N Yuen ldquoSeismic performance and designrequirements for high rise buildingsrdquo Structural Magazine pp28ndash32 2007
[3] J P Moehle ldquoPerformance-based seismic design of tall build-ings in the USrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[4] CEN EC8 Design of Structures for Earthquake ResistanceEuropean Committee for Standardization Brussels Belgium2004
[5] NZS 3101 Part 12006 Concrete Structures Standards NewZealand Standards New Zealand Wellington New Zealand2006
[6] T Paulay and M J N Priestley Seismic Design of ReinforcedConcrete and Masonry Buildings Wiley Hoboken NJ USA1992
[7] M Panagiotou J I Restrepo and J P Conte ldquoShake table test ofa 7-story full scale reinforced concrete structural wall buildingslice phase I rectangular wallrdquo Report SSRP 07-07 Departmentof Structural Engineering University of California San DiegoSan Diego Calif USA 2007
[8] Canadian Standard Association CSA Standard A233-04Design of Concrete Structures Canadian Standard AssociationRexdale Canada 2005
[9] R Klemencic J A Fry J D Hooper and B G MorgenldquoPerformance-based design of ductile concrete core wall build-ingsmdashissues to consider before detailed analysisrdquoTheStructuralDesign of Tall and Special Buildings vol 16 no 5 pp 599ndash6142007
[10] R Klemencic ldquoPerformance based seismic designmdashrisingrdquoStructural Magazine 2008 httpwwwstructuremagorgwp-contentuploads201408C-StructuralPractices-Klemencic-June081pdf
[11] A Zekioglu M Willford L Jin and M Melek ldquoCase studyusing the Los Angeles tall buildings structural design councilguidelines 40-storey concrete core wall buildingrdquo StructuralDesign of Tall and Special Buildings vol 16 no 5 pp 583ndash5972007
[12] B R Rad and P Adebar ldquoDynamic shear amplification inhigh-rise concrete walls effect of multiple flexural hinges andshear crackingrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[13] M Panagiotou and J I Restrepo ldquoDual-plastic hinge designconcept for reducing higher-mode effects on high-rise can-tilever wall buildingsrdquo Earthquake Engineering and StructuralDynamics vol 38 no 12 pp 1359ndash1380 2009
[14] M Ahmed and P Warnitchai ldquoReduction of inelastic seismicdemands by inducing plastic hinges at effective locationsrdquoin Proceedings of the 3rd Asian Conference on EarthquakeEngineering (ACEE rsquo10) Bangkok Thailand December 2010
[15] A Munir and P Warnitchai ldquoThe cause of unproportion-ately large higher mode contributions in the inelastic seismicresponses of high-rise core-wall buildingsrdquo Earthquake Engi-neering amp Structural Dynamics vol 41 no 15 pp 2195ndash22142012
[16] A Munir and P Warnitchai ldquoOptimal reduction of inelasticseismic demands in high-rise reinforced concrete core wallbuildings using energy-dissipating devicesrdquo Structural Design ofTall and Special Buildings vol 22 no 7 pp 543ndash568 2013
[17] M C Constantinou and M D Symans ldquoExperimental andanalytical investigation of seismic response of structures withsupplemental fluid viscous dampersrdquo NCEER Reports 92-0032State University of New York at Buffalo Buffalo NY USA 1992
[18] A SWhittaker V V Bertero C LThompson and L J AlonsoldquoSeismic testing of steel plate energy dissipation devicesrdquoEarthquake Spectra vol 7 no 4 pp 563ndash604 1991
[19] G W Housner L A Bergman T K Caughey et al ldquoStruc-tural control past present and futurerdquo Journal of EngineeringMechanics vol 123 no 9 pp 897ndash971 1997
[20] M D Symans F A Charney A S Whittaker et al ldquoEnergydissipation systems for seismic applications current practiceand recent developmentsrdquo Journal of Structural Engineering vol134 no 1 pp 3ndash21 2008
[21] C J Black N Makris and I D Aiken ldquoComponent testingseismic evaluation and characterization of buckling-restrainedbracesrdquo Journal of Structural Engineering vol 130 no 6 pp880ndash894 2004
[22] S Keten A performance based approach for seismic designwith hysteretic dampers [MS thesis] Massachusetts Institute ofTechnology (MIT) 2006 httpdspacemitedubitstreamhan-dle172113459571252112-MITpdfsequence=2
[23] N Anwar J A Sy T H Aung and D Rayamajhi ldquoFirstapplication of buckling restraint brace system in Philippines ina 50-story building with ductile core wall and PT slab systemrdquoin Proceedings of the 9th International Conference on UrbanEarthquake Engineering and the 4th Asia Conference on Earth-quake Engineering Tokyo Institute of Technology Tokyo JapanMarch 2012
[24] Computers and Structures Inc ETABS Extended 3D Analysis ofBuilding Systems Software Nonlinear Version 900 Computersand Structures Inc Berkeley Calif USA 2005
[25] Computers and Structures Perform 3D Nonlinear Analysis andPerformance Assessment for 3D Structures User Guide Version 4Computers and Structures Berkeley Calif USA 2006
Shock and Vibration 15
[26] J W Wallace and J P Moehle ldquoDuctility and detailing require-ments of bearing wall buildingsrdquo Journal of Structural Engineer-ing vol 118 no 6 pp 1625ndash1644 1992
[27] P Adebar A M M Ibrahim and M Bryson ldquoTest of high-risecore wall effective stiffness for seismic analysisrdquo ACI StructuralJournal vol 104 no 5 pp 549ndash559 2007
[28] FEMA ldquoPrestandard and commentary for the seismic rehabil-itation of buildingsrdquo FEMA 356 Federal Emergency Manage-ment Agency Washington DC USA 2000
[29] LATBDSC An Alternative Procedure for Seismic Analysis andDesign of Tall Buildings Located in Los Angeles Region A Con-sensus Document Los Angeles Tall Buildings and StructuralDesign Council 2008
[30] PEERNGAData Base Pacific Earthquake Engineering Research(PEER) University of California Berkeley Calif USA 2005httppeerberkeleyedunga
[31] COSMOS Data Base ldquoConsortium of organization for strong-motion observation systemsrdquo Tech Rep University of Cali-fornia Berkeley Calif USA 1999ndash2007 httpwwwcosmos-eqorgscriptsdefaultplx
[32] K Lilhanand and W S Tseng ldquoDevelopment and applicationof realistic earthquake time histories compatible with multipledamping design spectrardquo in Proceedings of the 9th World Con-ference on Earthquake Engineering Tokyo Japan August 1988
[33] J Hancock J Watson-Lamprey N A Abrahamson et al ldquoAnimproved method of matching response spectra of recordedearthquake ground motion using waveletsrdquo Journal of Earth-quake Engineering vol 10 no 1 pp 67ndash89 2006
[34] J B Mander M J N Priestley and R Park ldquoTheoreticalstress-strain model for confined concreterdquo Journal of StructuralEngineering New York vol 114 no 8 pp 1804ndash1826 1988
[35] CTBUH Seismic Working Group CTBUH Recommendationsfor the Seismic Design of High-Rise Buildings A ConsensusDocument 2008
[36] N Satake K-I Suda T Arakawa A Sasaki and Y TamuraldquoDamping evaluation using full-scale data of buildings inJapanrdquo Journal of Structural Engineering vol 129 no 4 pp 470ndash477 2003
[37] Q Xie ldquoState of the art of buckling-restrained braces in AsiardquoJournal of Constructional Steel Research vol 61 no 6 pp 727ndash748 2005
[38] P Clark K Kasai I Aiken E Ko and I Kimura ldquoDesign proce-dures for buildings incorporating hysteretic energy dissipatingdevicesrdquo in Proceedings of the 68th Annual Convention Struc-tural Engineers Association of California Santa Barbara CalifUSA October 1999
[39] D Vafaei and R Eskandari ldquoSeismic response of mega buck-ling-restrained braces subjected to fling-step and forward-directivity near-fault ground motionsrdquo Structural Design of Talland Special Buildings vol 24 no 9 pp 672ndash686 2015
[40] L Di Sarno and A S Elnashai ldquoBracing systems for seismicretrofitting of steel framesrdquo Journal of Constructional SteelResearch vol 65 no 2 pp 452ndash465 2009
[41] A Dutta and R O Hamburger ldquoCase study of A 40-Storeybuckling-restrained braced frame building located in LosAnge-lesrdquo The Structural Design of Tall and Special Buildings vol 19no 1-2 pp 77ndash93 2010
[42] Rutherford amp Chekene ldquoPerform nonlinear component mod-elling of star seismic powercat BRBsrdquo Report to Star SeismicLLC Star Seismic LLC 2011
[43] P Dusicka A M Itani and I G Buckle ldquoCyclic response ofplate steels under large inelastic strainsrdquo Journal of Construc-tional Steel Research vol 63 no 2 pp 156ndash164 2007
[44] S A Razavi M E Shemshadian S R Mirghaderi and SAhlehagh ldquoSeismic design of buckling restrained braced frameswith reduced core lengthrdquo in Proceedings of the The StructuralEngineers World Congress Cernobbio Italy 2011
[45] S A Razavi S R Mirghaderi A Hosseini and M EShemshadian ldquoReduced length buckling restrained brace usingsteel plates as restraining segmentrdquo in Proceedings of the 15thWorld Conference on Earthquake Engineering Lisboa PurtagalSeptember 2012
[46] M E Shemshadian S A Razavi S R Mirghaderi A Hosseiniand M K Mohammadi ldquoThe advantages of reducing thelength of yielding segment in seismic performance of bucklingrestrained braced framesrdquo inProceedings of the 6th InternationalConference of Seismology and Earthquake Engineering TehranIran 2011
[47] N Ma B Wu J Zhao H Li J Ou andW Yang ldquoFull scale testof all-steel buckling restrained bracesrdquo in Proceedings of the 14thWorld Conference on Earthquake Engineering Beijing ChinaOctober 2008
[48] L Di Sarno and G Manfredi ldquoSeismic retrofitting of existingRC frames with buckling restrained bracesrdquo in Proceedings ofthe Improving the Seismic Performance of Existing Buildingsand Other Structures pp 741ndash752 San Francisco Calif USADecember 2009
[49] S Ahlehagh Improvement of the special concentrically bracedsteel frames behaviour by employing balanced braces [MSthesis] University of Tehran Tehran Iran 2008
[50] R Tremblay P Bolduc R Neville and R DeVall ldquoSeismic test-ing and performance of buckling-restrained bracing systemsrdquoCanadian Journal of Civil Engineering vol 33 no 2 pp 183ndash1982006
Response spectra of scaled ground motionsSH-PR-360 times 30HM-H-090 times 40LP-HSP-000 times 15CM-EUR-090 times 40Hon-MGH-EW times 40Chichi-Taipei-090 times 60Imp-Ch-012 times 40
DBE spectrum (UBC-97 zone 4 SD)MCE spectrum (DBE spectrum times 15)
0
05
1
15
2
0 1 2 3 4 5 6 7 8 9 10Natural period (s)
0 1 2 3 4 5 6 7 8 9 10Natural period (s)
Spec
tral
acc
(g)
Spec
tral
acc
(g)
Target spectra
Figure 2 Comparison of the matched spectra of the groundmotions with DBE and MCE spectra
20 and 600mm times 600mm from Level 21 to Level 40) and200mm-thick posttensioned concrete flat slabs resting on theperipheral columns and the central core wall There are dooropenings in the wallThese openings are covered by couplingbeams The size of coupling beams is 600mm times 1500mmabove lobby level and 750mmtimes 800mm fromLevel 3 to Level20 whereas it is 600mm times 700mm from Levels 21 to 40Thecompressive strength of concrete for columns and walls is setto 55MPa up to Level 20 and 42MPa from Level 20 to theroof The reinforcing bars are Grade-60 steel with specifiedyield strength of 420MPa The central core wall forms thelateral load resisting system whereas posttensioned slabsand peripheral columns shall mainly form the gravity loadresisting system The gravity load includes self-weight of thestructure dead loads of 192 kNm2 and live loads of 24 kNm2
22 DBEElasticModal Demands byModal Response SpectrumAnalysis The modal response spectrum analysis (MRSA) ofthe building is performed using UBC-97 [1] design basisresponse spectrum for seismic zone-4 and soil type SD for5 damping in the single mode of vibration The responsespectrum is shown in Figure 2 The building is analysed in
the119883-direction only for brevity and considered sufficient forthe purpose of this study The commercial software ETABS[24] is used for MRSA procedure First six modes are foundto be sufficient for 90 mass participation in the MRSAHowever results show that both shear and moment demandsare mainly dominated by first four modes The combineddemands are obtained by combining individual modaldemands using CQC method
DBE elastic demands in the core wall in first four domi-nantmodes as well as their combination are shown in Figures3(a) 3(b) 3(c) and 3(d) respectively Both shear andmomentdemands are dominated by 1st 2nd and 3rd mode whereasdeformation demands are dominated by the 1st mode onlyThese demands shall be used for preparation of model forNonlinear Response History Analysis and to find the criticallocations of the BRBsThe story racking deformation angle isthe shear deformation of the panel between wall and periph-eral columnsThis is equal to the conventional story drift ratiosubtracted by the floor inclination angle measured clockwisefrom a horizontal plane
3 Description of Model forNonlinear Response History Analysis andSelection of Ground Motions
The nonlinear model is implemented in Commercial Soft-ware Perform-3D [25] The core wall is modelled using 22one-story high (3m) inelastic shear wall elements at theplastic hinge location at the base Each shear wall element wascomprised of 8 concrete and 8 steel fibres at the plastic hingelocations whereas the wall at other locations is modelled asthe 22 linear elastic shear wall elements The previous studies[26 27] show that plastic hinge length of the high-rise wallmay be taken as 12 to 23 times wall length (Lw) The lengthof the wall in this case is 10m Therefore plastic hinges wereallowed over two-story height (6m) which is approximately23 Lw However one-story high inelastic shear wall elementswere used over the plastic hinge length based on section68222 of FEMA-356 [28] which mentions that plastichinge length should be smaller than one-story height or Lw2
The flexural strength at the plastic hinge location shouldbe as low as possible to allow early yielding of the wall but atthe same time plastic hinge rotation as well as related defor-mation demands such as story drift and racking shear defor-mation should bewithin permissible limits In this study flex-ural strength is based on the DBE design moment demandsdetermined by code based procedure of UBC-97 [1] Theseare larger than the values obtained either (a) by dividing thecombined elastic demands by appropriate response modifi-cation factor ldquo119877rdquo of 55 or (b) by dividing ldquo119877rdquo factor requiredto satisfy the requirement of 90 of the base shear obtainedfrom static analysis procedure There are mainly two reasonsfor setting flexural strength in this way (1) this is based on thestandard code based design such as UBC-97 [1] (2) moderncode such as LATBDC-2008 [29] recommend capacity designas a first step of the performance based design and designersare using the code based design as the initial step and later
4 Shock and Vibration
minus5
0
5
10
15
20
25
30
35
40
0 3 6
Leve
l num
ber
CombinedMode-1Mode-2
Mode-3Mode-4
Moment (kNmiddotm times 106)
(a)
minus5
0
5
10
15
20
25
30
35
40
Leve
l num
ber
0 50 100
CombinedMode-1Mode-2
Mode-3Mode-4
Shear (kN times 103)
(b)
minus5
0
5
10
15
20
25
30
35
40
0 025 05 075 1
Leve
l
Displacement (m)
CombinedMode-1Mode-2
Mode-3Mode-4
(c)
minus5
0
5
10
15
20
25
30
35
40
Leve
l
0 001Racking shear deformation ratio
002
CombinedMode-1Mode-2
Mode-3Mode-4
(d)
Figure 3 DBE elasticmodal and total seismic demands (a)Moment demands (b) shear demands (c) displacement demands and (d) rackingshear deformation demands
confirm the performance at MCE level by the NLRHAprocedure
Plastic hinges are also induced at both ends of cou-pling beams The characteristics of the plastic hinges aredetermined by beam cross section properties and flexural
reinforcement worked out based on the design demands andassumed plastic hinge length of 05 times the depth of thebeam The remaining portion of the coupling beam is mod-elled as elastic beam element A trilinear moment-curvaturerelationship without stiffness and strength degradation is
Shock and Vibration 5
Stre
ss
Strain
Stre
ss
Strain
Unloading and reloading arethe same in case of tension
Steel material Concrete material
Mander envelopePerform-3D UnloadingReloading
f998400cc
Eo
EoEo
dcEo
120585998400cc120585998400c120585cu
ft
fu
fy
Park envelopePerform-3D Cyclic
120585y 120585sh 120585u
fy rebar yield stressfu rebar ultimate stress capacity120585y rebar yield strain120585sh strain in rebar at the onset of strain hardening120585y rebar ultimate strain capacityEo modulus of elasticiy
f998400c compressive strength of unconfined concrete
f998400cc compressive strength of confined concrete
120585998400c concrete strain atf998400c
120585998400cc concrete strain atf998400cc
120585cu ultimate strain capacity for confined concreteEo tangent modulus of elasticitydc energy dissipation factor for the reloading stiffnessft tensile strength of concrete = 75radicf998400
c (f998400c is in psi)
Figure 4 Nonlinear Park Steel and Manderrsquos concrete model
used for modelling plastic hinges at the ends of couplingbeams All slabs and columns aremodelled by elastic slab andcolumn elements of the Perform-3D respectively
Seven set of ground motions are selected from PEER[30] and COSMOS [31] data bases The ground motionsinclude both short distance moderate and long distancelarge magnitude earthquake The selected ground motionsare first roughly scaled up or down by a constant factor toapproximately match the target MCE spectrum The roughlyscaled ground motions are then matched to the MCE targetspectrum by using time domain spectral matching techniqueof [32] The software RSP match [33] is used for this purposeThe target spectrum and spectra of seven spectrally matchedtime history used in this study are shown in Figure 2 Non-linearmaterial models similar to those proposed by [34] wereassigned for rebarrsquos and concrete material respectively asshown in Figure 4 The modal damping is set as per recom-mendations of [35] CTBUH (2008) and [36]
4 Analysis of Structure without BRBs
The controlled structure described in Section 3 is analysedfor seven sets of ground motions The shear and momentdemands obtained are shown in Figure 5 These results showthat base shear demand is about 15 of the total building
weight Similarly moment demand is also very high at midheight However at the base the moment demand is clippedto the flexural strength of plastic hinge If the wall is designedfor mid height moment to remain elastic and hence nodamage there shall be reinforcement congestion On theother hand if plastic hinge is allowed at mid height the corewall shall be subjected to high rotational demands and hencedamage near themid height of thewall in addition to the baseTo reduce damage at the base of the wall as well as reducemid height moment to avoid reinforcement congestion analternative strategy using different arrangements of buck-ling restrained braces (energy dissipating devices) has beenevolved in the next section (Options-2ndash4) and results arecompared with the controlled structure (Option-1)
5 Buckling Restrained Braces Evolvement ofStrategies for Efficient Locations Their Sizeand Modelling
51 Buckling Restrained Brace An ordinary brace exhibitsunstable hysteretic behaviour due to buckling in compres-sion hence it cannot dissipate much energy To avoid com-pression buckling and to achieve more energy dissipationanother brace known as buckling restrained brace (BRB) hasbeen introduced This type of brace exhibits stable hysteric
6 Shock and Vibration
0 40 80 120
Mean MCE demands Mean MCE demands
0 1 2 3minus5
0
5
10
15
20
25
30
35
40
Leve
l num
ber
minus5
0
5
10
15
20
25
30
35
40
Leve
l num
ber
Shear (kN times 103) Moment (kNmiddotm times 106)
Figure 5 Inelastic MCE shear and moment demands in the controlled structure
Encasing mortar
Yielding steel core
Steel tube
Unbonding materialbetween steel core
and mortar
Figure 6 Typical BRB
behaviour because its compression buckling is avoided due toencasing by an outer steel tubeThemain brace and outer tubeare separated by bonding material in order to accommodatethe lateral expansion due to its compression yielding [37] Atypical BRB is shown in Figure 6 [38]
52 Location of Buckling Restrained Braces BRBs have beeninstalled at several critical locations based on the results ofelastic modal decomposition analysis in dominant modessuch as 1st 2nd and 3rd modes and results are comparedwith controlled structure described in Section 4 (Option-1)In second option (Option-2) the BRBs have been installed
at bays 2 3 and 4 between peripheral columns and centralcore wall based on the maximum racking shear deformationdemands in 2nd and 3rd modes This arrangement is shownin Figure 7 In third option small size BRBs have also beeninstalled at bays 2 and 4 in cut in central core wall at the max-imum moment demands in 2nd and 3rd modes These BRBsare in addition to the BRBs in Option-2 This arrangementis shown in Figure 8 In final and fourth option (Option-4)BRBs have been installed in cut in central core wall at bays 2and 4 at the location of maximum shear force in 2nd and 3rdmodes in addition to the BRBs in Option-2 This is shownin Figure 9 It may be noted that the locations of BRBs in
Shock and Vibration 7
0
5
10
15
20
25
30
35
40
0
000
1
000
2
000
3
000
4
000
5
Leve
l
Racking shear deformation ratioMode-2Mode-3
Mode-4
Figure 7 Arrangement of the BRBs at locations of maximum racking shear deformation in exterior panels (Option-2)
0
5
10
15
20
25
30
35
40
0 1 2 3
Leve
l
0
5
10
15
20
25
30
35
40
Leve
l
Mode-2Mode-3
Mode-4 Mode-2Mode-3
Mode-4
Moment (kNmiddotm times 106)
0
000
1
000
2
000
3
000
4
000
5
Racking shear deformation ratio
Figure 8 Arrangement of the exterior BRBs at locations of maximum DBE elastic racking shear deformation in 2nd and 3rd mode andinterior BRBs at locations of maximum DBE elastic moment demands in 2nd and 3rd mode (Option-3)
8 Shock and Vibration
0
5
10
15
20
25
30
35
40Le
vel
0
5
10
15
20
25
30
35
40
0 50 100
Leve
l num
ber
Shear (kN times 103)
Mode-2Mode-3
Mode-4 Mode-2Mode-3
Mode-4
0
000
1
000
2
000
3
000
4
000
5
Racking shear deformation ratio
Figure 9 Arrangement of the exterior BRBs at locations of maximum DBE elastic racking shear deformation in 2nd and 3rd mode andinterior BRBs at locations of maximum DBE elastic shear demands in 2nd and 3rd mode (Option-3)
Option-1 Option-2 andOption-3 are also suitable for mode-1
The BRBs dissipate energy through axial tension andcompression To achieve maximum energy dissipation theBRBs should be placed at the proper locations and anglesEach BRB has been placed at an angle of approximately1205874 covering almost three stories for exterior brace and twostories for brace in cut in core wall These V-shaped BRBsconfigurations resemble the BRBs configuration used inmegabraced frames steel buildings reported in the previous studies[39ndash41] BRBs shall cross the slabs through purposely builtopenings provided in the slabs A horizontal drag elementis used from point where BRB connects to the column tothe central core wall to take care of the horizontal forcecomponent of the BRB axial force at column connection
53 Size of Buckling Restrained Braces Sizes of the BRBs havebeen selected by hit and trial using more rigorous nonlineartime history analyses (NLTHAs) using displacement-baseddesign approach Their size should neither be too large tobe uneconomical nor be too small to be ineffective The 119883-section of the braces between peripheral columns and centralcore wall is selected as 7500mm2 whereas it is 3750mm2for braces in cuts in core wall The buckling restrained bracesmanufactured by star seismic with normal yield strength of280MPa are used for braces between peripheral columnsand central core wall [42] However the low yield point-100(LYP100) steel core manufactured by Nippon Steel Corpora-tion Japan with specified yield strength of 100MPa is used
f
0DXDU
FY
FUO
FUH
KF
KO
Figure 10 Trilinear curve for BRBs
for braces in cut elements [22]The lowyield point steel bracesare used in cut in core wall to mainly achieve more energydissipation through the early yielding of the brace [43]
54 Modelling of Buckling Restrained Braces A BRB consistsof three components that is central yielding core brace endsmember connecting the central brace with the pin connec-tion and pin connection between brace and main structuralmembers The length of the exterior core brace is 45mwhereas length of the core brace in cut of core wall is 18mThese lengths are in the optimum range of 02ndash04 times thetotal length of the brace Several advantages such as simple
Shock and Vibration 9
minus4000
minus3000
minus2000
minus1000
0
1000
2000
3000
4000A
xial
forc
e ( k
N)
Axial def (m)
10E minus 0150E minus 0200E + 00minus50E minus 02
(a)
minus500
minus400
minus300
minus200
minus100
0
100
200
300
400
500
Axi
al fo
rce (
kN
)
Axial def (m)
20E
minus03
10E
minus03
00E
+00
minus30E
minus03
minus20E
minus03
minus10E
minus03
(b)
Figure 11 Typical cyclic response of BRBs obtained from the analysis (a) Exterior brace (b) interior brace
replacement lesser weight concrete elimination economyand easy erection process are associated with reduced lengthof the core brace [44ndash50] BRB has been modelled using theBRB compound component of the Perform-3D Such mem-ber is composed of three components that is (1) a BRB basiccomponent for main yielding brace (2) an elastic bar basiccomponent for member connecting brace with gusset plateand (3) a stiff end zone which accounts for the gusset platesand so forth at both ends of the member
The positive side (tension) of the trilinear curve to definethe force-deformation of the BRBs is shown in Figure 10 Itcan be seen that after yielding there are two lines such asbottom and top line The bottom line is used to simulate firstcyclic load and the top line is used to simulate full strainhardening The same behavior has been observed in testslike the hysteresis loop which can progressively grow in sizeThis is sometimes referred to as ldquoisotropic hardeningrdquo Thisleads to the component increase in strength under cyclic loadThe negative side of the curve shows a little variation due todifference in the values of compression and tensions FY FUO(FUO (T) = 105 FY FUO (C) = 104 FY) and FUH (FUO(T) = 134 FY FUO (C) = 151 FY) are yield strength strengthat first loading cycle and strength of the core brace afterfull hardening respectively DU (DU (T) = 07 DU (C) =07) is the deformation at FUO and DX (DX (T) = 004 LYCDX (C) = 004 LYC) is the maximum deformation of thebrace LYC is the length of the yielding core KO is theInitial stiffness of the core brace and KF (= 002KO) is theslope of third line [42] The strain hardening properties suchas deformation at FUO-FUH average are taken equal to 2times (LYC180) and deformation at FUH is taken as 35times (LYC180) The typical force-deformation relationshipfor exterior (between peripheral columns and core wall) andinterior BRB (in cut in core wall) obtained from NLRHAanalysis for a particular ground motion is shown in Figures11(a) and 11(b) respectivelyThese figures show that hysteresisloop is similar to the reported Clark et al 1999 [38] provingthat performing BRB element can capture the behaviour
appropriately The size of the elastic bar element is selectedsuch that it can safely carry maximum axial force in brace inelastic range to conform to the capacity design approach Stiffend zone is few times stiffer than the elastic bar element
6 Comparison of the Responses in DifferentOptions and Discussion on the Results
NLRHA is performed using seven spectrally matched timehistories Different response quantities such as displacementplastic hinge rotations in coupling beams and core wall sheardeformation angle (story racking shear deformation) bend-ing moment shear force and energy demands are obtainedfrom this analysisThe plastic rotations are calculated bymul-tiplying the average curvature of the wall at mid height withthe plastic hinge length The mean value of different quan-tities obtained from seven ground motions are shown anddiscussed in following paragraphs
Shear demands obtained from four options are shownin Figure 12(a) Shear demand pattern and magnitude aresimilar in all options Moment demands obtained from fouroptions are shown in Figure 12(b) The moment demand atthe base is similar in all four options because this is clippedto the flexural strength of the plastic hinge at the base of thewall However it is reduced along the wall height by 30 35and 40 in Option-2 Option-3 and Option-4 respectivelyin comparison to that in 1st optionThe reduction inmomentdemand is significant in all options This will help to avoidreinforcement congestion in the wall near mid height
Displacement demands obtained from four options areshown in Figure 13(a) Displacement demand pattern is simi-lar for all options However displacement demand is reducedalong thewall height by 40 40 and 60 inOption-2 Option-3 and Option-4 respectively in comparison to that in 1stoption Racking shear deformation demands obtained fromfour options are shown in Figure 13(b) The racking sheardeformation demand patterns are similar for all four optionsHowever racking shear deformation demands are reduced
10 Shock and Vibration
minus5
0
5
10
15
20
25
30
35
40
0 50000 100000 150000
Leve
l
Shear force (kN)
Option-1Option-2
Option-3Option-4
(a)
minus5
0
5
10
15
20
25
30
35
40
Leve
l
0 1 2 3
Option-1Option-2
Option-3Option-4
Bending moment (kNmiddotm times 106)
(b)
Figure 12 MCE inelastic shear and moment demands in different options (a) Shear (b) moment
0 05 1 15 2 25Displacement (m)minus5
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(a)
0 001 002 003 004Racking shear deformation ratio
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(b)
Figure 13 MCE inelastic displacement and racking deformation demands in different options (a) Displacement (b) racking sheardeformation angle
along the wall height by 40 40 and 65 in Option-2Option-3 and Option-4 respectively in comparison to thatin 1st option This is significant reduction Racking sheardeformations of 0036 in the controlled structures are reducedto 0023 which is well within the limit of 003 set by [29]LATBSDC 2008 for the MCE level earthquake
Rotational demands in the core wall at the base level aswell as in coupling beams along the height are shown in Fig-ures 14(a) and 14(b) respectivelyThe rotation demand in thewall is calculated by multiplying the average curvature at themid height of the inelastic wall element by height of the wallThe comparison shows that themaximum rotational demand
at the base of the wall is reduced by 99 57 and 93 inOption-2Option-3 andOption-4 respectively in comparison to thatin 1st option This is strong indication that damage at thebase of the wall shall be reduced to half and consequentlyextent of repair shall be small and hence cheap in case ofsevere MCE events such as DBE and MCE level earthquakeThe rotational demands in coupling beams are reduced by52 40 and 35 respectively above the half height level forOption-2 Option-3 and Option-4 respectively in compar-ison to 1st option However rotation demand remained thesame in the lower half portion of the building for all options
Energy dissipated by core wall coupling beams andbuckling restrained braces have been compared in Figures15(a)ndash15(d) respectively for Option-1 Option-2 Option-3 and Option-4 respectively This is energy dissipated inpercentage of the total energy demand in the structure Thetotal energy demand is sum of the kinetic energy elasticstrain energy energy dissipated by elastic modal dampingand energy dissipation by damage in structural elements suchas core wall coupling beams and BRBs About 83 9292 and 90 energy have been dissipated by elastic modaland inelastic damping in Option-1 to Option-4 respectivelyThe energy dissipation by modal elastic damping to the totalenergy demands is 50 37 35 and 33 respectively inOption-1 to Option-4 respectivelyThe energy dissipation bycore wall at the base to the total energy demands is 22 66 and 6 inOption-1 to Option-4 respectivelyThe energydissipation by coupling beams to the total energy demands isapproximately 10 4 5 and 6 in Option-1 to Option-4 respectively The energy dissipation by BRBs to the total
energy demands is 0 45 45 and 45 respectively inOption-1 to Option-4
7 Effects of BRBs on Axial Loads Shearand Moment of Columns and PermanentDeformation due to BRBs Plastification
Effects of BRBs on axial loads of columns and permanentdeformation due to BRBs plastification have been discussedin this section The axial load envelope in a typical columnfor Options-1ndash4 is shown in the Figure 16 The magnitude ofaxial load is same for Options-2ndash4 (with BRBs) and is twicethan that in Option-1 (controlled structure) This is due tothe outrigger effect created by the connection of columnsand core wall through BRBs Some core wall moment hasbeen resisted by the development of axial push-pull in thecolumns Furthermore the shape of the axial load envelopeis smooth in case of Option-1 whereas it is jagged at thelocations of the BRBs forOptions-2ndash4Themoment envelopeand shear envelope for one typical column are shown inFigures 17(a) and 17(b) respectively It shows that momentand shear have been reduced at the ground level in Options-2ndash4 in comparison to Option-1 whereas these remain almostthe same at upper portions The extra moment and shearat the ground level in Options-1ndash4 is due to the transfer ofmoment and shear to the columns when core wall yields
To better understand the permanent deformation in thestructure due to BRBs plastification cyclic pushover analysisin firstmode is performedusing target displacement obtainedfrom NLTHA for all cases The cyclic base shear versus top
12 Shock and Vibration
Option-1
0
20
40
60
80
100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 53478kNmiddotm
(a)
Option-2
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 73328kNmiddotm
(b)
Option-3
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80 90
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 71449kNmiddotm
(c)
Option-4
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 69558kNmiddotm
(d)
Figure 15 Inelastic energy demands in structural components (a) to (d) For Option-1 to Option-4 respectively
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus20000 minus10000 0
Leve
l
Axial load (kN)
Option-1Option-2
Option-3Option-4
Figure 16 Axial load envelope in one typical column
Shock and Vibration 13
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus15000 0 15000 30000
Leve
l
minus5
0
5
10
15
20
25
30
35
40
Leve
l
Moment (kNmiddotm)
minus1200 minus800 minus400 0 400 800 1200
Shear (kN)
Option-1Option-2
Option-3Option-4
Option-1Option-2
Option-3Option-4
Figure 17 Moment and shear envelope in one typical column
minus20 minus10 00 10 20
Base
shea
r (kN
)
Top displacement (m)
Option-1Option-2
Option-3Option-4
300E + 04
200E + 04
100E + 04
000E + 00
minus100E + 04
minus200E + 04
minus300E + 04
Figure 18 Base shear versus top displacement relationship in firstmode load pattern
displacement is compared in Figure 18 It can be seen that thiscurve is flag shaped for Option-1 whereas it is bilinear pinch-ing type in Options-2ndash4There is no permanent deformationin controlled structure and flag shaped hysteresis behaviouris observed The same behaviour was observed during testconducted on a large-scale model of a concrete shear wallfrom the core of a high-rise building in the study of Adebar etal [27] The combination of low percentage of vertical rein-forcement and large axial compression force due to gravity
loads (axial force(concrete 28 days cylinder strength times grossarea ofwall)gt 01) caused the flexural cracks to closewhen thelateral load was removed In Options-2ndash4 small permanentdeformation (residual displacement) is observed This isbecause of the plastification of BRBs as well as transfer of themoment demand from shear wall to columns in the form ofaxial push-pull
8 Conclusions
(i) In this study different options of location of BRBsare investigated for a 40-story case study buildingThe locations of BRBs are identified based on theDBE elastic racking shear deformation and shear andbending moment demands in dominant 2nd and 3rdmodes NLRHA is then performed for seven sets ofspectrally matched target time histories and resultsare compared for different options
(ii) In all options shear force demands bending momentat mid height displacement demand racking sheardeformation demand and rotation demand in cou-pling beams are reduced by 10 45 45 45 and40 respectively in comparison to the controlledstructure
(iii) Rotational demand in the core wall at base level isreduced by 99 57 and 93 in Option-2 Option-3 and Option-4 respectively in comparison toOption-1Whereas energy dissipated by the core wallis reduced by around 250 in the corewall in compar-ison to the controlled structure Rotational demandand energy dissipation are measure of damage in thecore wall Thus damage can be significantly reducedby installation of BRBs
14 Shock and Vibration
(iv) All BRBs options are effective for bending momentreduction at mid height displacement and rackingshear deformation demands along the wall heightand rotation demand at the base of the wall and incoupling beams above the mid height of the build-ing However Option-4 in which BRBs are installedbetween peripheral columns and central corewall andcut in shear walls based on the maximum shear forceand bending moment leads to the highest reductionThis is because of the early yielding of the interiorbraces
(v) Thiswork is equally important for academia and prac-tising engineers especially those working in the fieldof performance based design of the high-rise build-ings in the commercial consultancy This will helpthem to locate BRBs at appropriate locations whiledesigning their buildings in an optimal way
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] International Conference of Building Officials Uniform Build-ing Code vol 2 International Conference of Building OfficialsWhittier Calif USA 1997
[2] J Maffei and N Yuen ldquoSeismic performance and designrequirements for high rise buildingsrdquo Structural Magazine pp28ndash32 2007
[3] J P Moehle ldquoPerformance-based seismic design of tall build-ings in the USrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[4] CEN EC8 Design of Structures for Earthquake ResistanceEuropean Committee for Standardization Brussels Belgium2004
[5] NZS 3101 Part 12006 Concrete Structures Standards NewZealand Standards New Zealand Wellington New Zealand2006
[6] T Paulay and M J N Priestley Seismic Design of ReinforcedConcrete and Masonry Buildings Wiley Hoboken NJ USA1992
[7] M Panagiotou J I Restrepo and J P Conte ldquoShake table test ofa 7-story full scale reinforced concrete structural wall buildingslice phase I rectangular wallrdquo Report SSRP 07-07 Departmentof Structural Engineering University of California San DiegoSan Diego Calif USA 2007
[8] Canadian Standard Association CSA Standard A233-04Design of Concrete Structures Canadian Standard AssociationRexdale Canada 2005
[9] R Klemencic J A Fry J D Hooper and B G MorgenldquoPerformance-based design of ductile concrete core wall build-ingsmdashissues to consider before detailed analysisrdquoTheStructuralDesign of Tall and Special Buildings vol 16 no 5 pp 599ndash6142007
[10] R Klemencic ldquoPerformance based seismic designmdashrisingrdquoStructural Magazine 2008 httpwwwstructuremagorgwp-contentuploads201408C-StructuralPractices-Klemencic-June081pdf
[11] A Zekioglu M Willford L Jin and M Melek ldquoCase studyusing the Los Angeles tall buildings structural design councilguidelines 40-storey concrete core wall buildingrdquo StructuralDesign of Tall and Special Buildings vol 16 no 5 pp 583ndash5972007
[12] B R Rad and P Adebar ldquoDynamic shear amplification inhigh-rise concrete walls effect of multiple flexural hinges andshear crackingrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[13] M Panagiotou and J I Restrepo ldquoDual-plastic hinge designconcept for reducing higher-mode effects on high-rise can-tilever wall buildingsrdquo Earthquake Engineering and StructuralDynamics vol 38 no 12 pp 1359ndash1380 2009
[14] M Ahmed and P Warnitchai ldquoReduction of inelastic seismicdemands by inducing plastic hinges at effective locationsrdquoin Proceedings of the 3rd Asian Conference on EarthquakeEngineering (ACEE rsquo10) Bangkok Thailand December 2010
[15] A Munir and P Warnitchai ldquoThe cause of unproportion-ately large higher mode contributions in the inelastic seismicresponses of high-rise core-wall buildingsrdquo Earthquake Engi-neering amp Structural Dynamics vol 41 no 15 pp 2195ndash22142012
[16] A Munir and P Warnitchai ldquoOptimal reduction of inelasticseismic demands in high-rise reinforced concrete core wallbuildings using energy-dissipating devicesrdquo Structural Design ofTall and Special Buildings vol 22 no 7 pp 543ndash568 2013
[17] M C Constantinou and M D Symans ldquoExperimental andanalytical investigation of seismic response of structures withsupplemental fluid viscous dampersrdquo NCEER Reports 92-0032State University of New York at Buffalo Buffalo NY USA 1992
[18] A SWhittaker V V Bertero C LThompson and L J AlonsoldquoSeismic testing of steel plate energy dissipation devicesrdquoEarthquake Spectra vol 7 no 4 pp 563ndash604 1991
[19] G W Housner L A Bergman T K Caughey et al ldquoStruc-tural control past present and futurerdquo Journal of EngineeringMechanics vol 123 no 9 pp 897ndash971 1997
[20] M D Symans F A Charney A S Whittaker et al ldquoEnergydissipation systems for seismic applications current practiceand recent developmentsrdquo Journal of Structural Engineering vol134 no 1 pp 3ndash21 2008
[21] C J Black N Makris and I D Aiken ldquoComponent testingseismic evaluation and characterization of buckling-restrainedbracesrdquo Journal of Structural Engineering vol 130 no 6 pp880ndash894 2004
[22] S Keten A performance based approach for seismic designwith hysteretic dampers [MS thesis] Massachusetts Institute ofTechnology (MIT) 2006 httpdspacemitedubitstreamhan-dle172113459571252112-MITpdfsequence=2
[23] N Anwar J A Sy T H Aung and D Rayamajhi ldquoFirstapplication of buckling restraint brace system in Philippines ina 50-story building with ductile core wall and PT slab systemrdquoin Proceedings of the 9th International Conference on UrbanEarthquake Engineering and the 4th Asia Conference on Earth-quake Engineering Tokyo Institute of Technology Tokyo JapanMarch 2012
[24] Computers and Structures Inc ETABS Extended 3D Analysis ofBuilding Systems Software Nonlinear Version 900 Computersand Structures Inc Berkeley Calif USA 2005
[25] Computers and Structures Perform 3D Nonlinear Analysis andPerformance Assessment for 3D Structures User Guide Version 4Computers and Structures Berkeley Calif USA 2006
Shock and Vibration 15
[26] J W Wallace and J P Moehle ldquoDuctility and detailing require-ments of bearing wall buildingsrdquo Journal of Structural Engineer-ing vol 118 no 6 pp 1625ndash1644 1992
[27] P Adebar A M M Ibrahim and M Bryson ldquoTest of high-risecore wall effective stiffness for seismic analysisrdquo ACI StructuralJournal vol 104 no 5 pp 549ndash559 2007
[28] FEMA ldquoPrestandard and commentary for the seismic rehabil-itation of buildingsrdquo FEMA 356 Federal Emergency Manage-ment Agency Washington DC USA 2000
[29] LATBDSC An Alternative Procedure for Seismic Analysis andDesign of Tall Buildings Located in Los Angeles Region A Con-sensus Document Los Angeles Tall Buildings and StructuralDesign Council 2008
[30] PEERNGAData Base Pacific Earthquake Engineering Research(PEER) University of California Berkeley Calif USA 2005httppeerberkeleyedunga
[31] COSMOS Data Base ldquoConsortium of organization for strong-motion observation systemsrdquo Tech Rep University of Cali-fornia Berkeley Calif USA 1999ndash2007 httpwwwcosmos-eqorgscriptsdefaultplx
[32] K Lilhanand and W S Tseng ldquoDevelopment and applicationof realistic earthquake time histories compatible with multipledamping design spectrardquo in Proceedings of the 9th World Con-ference on Earthquake Engineering Tokyo Japan August 1988
[33] J Hancock J Watson-Lamprey N A Abrahamson et al ldquoAnimproved method of matching response spectra of recordedearthquake ground motion using waveletsrdquo Journal of Earth-quake Engineering vol 10 no 1 pp 67ndash89 2006
[34] J B Mander M J N Priestley and R Park ldquoTheoreticalstress-strain model for confined concreterdquo Journal of StructuralEngineering New York vol 114 no 8 pp 1804ndash1826 1988
[35] CTBUH Seismic Working Group CTBUH Recommendationsfor the Seismic Design of High-Rise Buildings A ConsensusDocument 2008
[36] N Satake K-I Suda T Arakawa A Sasaki and Y TamuraldquoDamping evaluation using full-scale data of buildings inJapanrdquo Journal of Structural Engineering vol 129 no 4 pp 470ndash477 2003
[37] Q Xie ldquoState of the art of buckling-restrained braces in AsiardquoJournal of Constructional Steel Research vol 61 no 6 pp 727ndash748 2005
[38] P Clark K Kasai I Aiken E Ko and I Kimura ldquoDesign proce-dures for buildings incorporating hysteretic energy dissipatingdevicesrdquo in Proceedings of the 68th Annual Convention Struc-tural Engineers Association of California Santa Barbara CalifUSA October 1999
[39] D Vafaei and R Eskandari ldquoSeismic response of mega buck-ling-restrained braces subjected to fling-step and forward-directivity near-fault ground motionsrdquo Structural Design of Talland Special Buildings vol 24 no 9 pp 672ndash686 2015
[40] L Di Sarno and A S Elnashai ldquoBracing systems for seismicretrofitting of steel framesrdquo Journal of Constructional SteelResearch vol 65 no 2 pp 452ndash465 2009
[41] A Dutta and R O Hamburger ldquoCase study of A 40-Storeybuckling-restrained braced frame building located in LosAnge-lesrdquo The Structural Design of Tall and Special Buildings vol 19no 1-2 pp 77ndash93 2010
[42] Rutherford amp Chekene ldquoPerform nonlinear component mod-elling of star seismic powercat BRBsrdquo Report to Star SeismicLLC Star Seismic LLC 2011
[43] P Dusicka A M Itani and I G Buckle ldquoCyclic response ofplate steels under large inelastic strainsrdquo Journal of Construc-tional Steel Research vol 63 no 2 pp 156ndash164 2007
[44] S A Razavi M E Shemshadian S R Mirghaderi and SAhlehagh ldquoSeismic design of buckling restrained braced frameswith reduced core lengthrdquo in Proceedings of the The StructuralEngineers World Congress Cernobbio Italy 2011
[45] S A Razavi S R Mirghaderi A Hosseini and M EShemshadian ldquoReduced length buckling restrained brace usingsteel plates as restraining segmentrdquo in Proceedings of the 15thWorld Conference on Earthquake Engineering Lisboa PurtagalSeptember 2012
[46] M E Shemshadian S A Razavi S R Mirghaderi A Hosseiniand M K Mohammadi ldquoThe advantages of reducing thelength of yielding segment in seismic performance of bucklingrestrained braced framesrdquo inProceedings of the 6th InternationalConference of Seismology and Earthquake Engineering TehranIran 2011
[47] N Ma B Wu J Zhao H Li J Ou andW Yang ldquoFull scale testof all-steel buckling restrained bracesrdquo in Proceedings of the 14thWorld Conference on Earthquake Engineering Beijing ChinaOctober 2008
[48] L Di Sarno and G Manfredi ldquoSeismic retrofitting of existingRC frames with buckling restrained bracesrdquo in Proceedings ofthe Improving the Seismic Performance of Existing Buildingsand Other Structures pp 741ndash752 San Francisco Calif USADecember 2009
[49] S Ahlehagh Improvement of the special concentrically bracedsteel frames behaviour by employing balanced braces [MSthesis] University of Tehran Tehran Iran 2008
[50] R Tremblay P Bolduc R Neville and R DeVall ldquoSeismic test-ing and performance of buckling-restrained bracing systemsrdquoCanadian Journal of Civil Engineering vol 33 no 2 pp 183ndash1982006
Figure 3 DBE elasticmodal and total seismic demands (a)Moment demands (b) shear demands (c) displacement demands and (d) rackingshear deformation demands
confirm the performance at MCE level by the NLRHAprocedure
Plastic hinges are also induced at both ends of cou-pling beams The characteristics of the plastic hinges aredetermined by beam cross section properties and flexural
reinforcement worked out based on the design demands andassumed plastic hinge length of 05 times the depth of thebeam The remaining portion of the coupling beam is mod-elled as elastic beam element A trilinear moment-curvaturerelationship without stiffness and strength degradation is
Shock and Vibration 5
Stre
ss
Strain
Stre
ss
Strain
Unloading and reloading arethe same in case of tension
Steel material Concrete material
Mander envelopePerform-3D UnloadingReloading
f998400cc
Eo
EoEo
dcEo
120585998400cc120585998400c120585cu
ft
fu
fy
Park envelopePerform-3D Cyclic
120585y 120585sh 120585u
fy rebar yield stressfu rebar ultimate stress capacity120585y rebar yield strain120585sh strain in rebar at the onset of strain hardening120585y rebar ultimate strain capacityEo modulus of elasticiy
f998400c compressive strength of unconfined concrete
f998400cc compressive strength of confined concrete
120585998400c concrete strain atf998400c
120585998400cc concrete strain atf998400cc
120585cu ultimate strain capacity for confined concreteEo tangent modulus of elasticitydc energy dissipation factor for the reloading stiffnessft tensile strength of concrete = 75radicf998400
c (f998400c is in psi)
Figure 4 Nonlinear Park Steel and Manderrsquos concrete model
used for modelling plastic hinges at the ends of couplingbeams All slabs and columns aremodelled by elastic slab andcolumn elements of the Perform-3D respectively
Seven set of ground motions are selected from PEER[30] and COSMOS [31] data bases The ground motionsinclude both short distance moderate and long distancelarge magnitude earthquake The selected ground motionsare first roughly scaled up or down by a constant factor toapproximately match the target MCE spectrum The roughlyscaled ground motions are then matched to the MCE targetspectrum by using time domain spectral matching techniqueof [32] The software RSP match [33] is used for this purposeThe target spectrum and spectra of seven spectrally matchedtime history used in this study are shown in Figure 2 Non-linearmaterial models similar to those proposed by [34] wereassigned for rebarrsquos and concrete material respectively asshown in Figure 4 The modal damping is set as per recom-mendations of [35] CTBUH (2008) and [36]
4 Analysis of Structure without BRBs
The controlled structure described in Section 3 is analysedfor seven sets of ground motions The shear and momentdemands obtained are shown in Figure 5 These results showthat base shear demand is about 15 of the total building
weight Similarly moment demand is also very high at midheight However at the base the moment demand is clippedto the flexural strength of plastic hinge If the wall is designedfor mid height moment to remain elastic and hence nodamage there shall be reinforcement congestion On theother hand if plastic hinge is allowed at mid height the corewall shall be subjected to high rotational demands and hencedamage near themid height of thewall in addition to the baseTo reduce damage at the base of the wall as well as reducemid height moment to avoid reinforcement congestion analternative strategy using different arrangements of buck-ling restrained braces (energy dissipating devices) has beenevolved in the next section (Options-2ndash4) and results arecompared with the controlled structure (Option-1)
5 Buckling Restrained Braces Evolvement ofStrategies for Efficient Locations Their Sizeand Modelling
51 Buckling Restrained Brace An ordinary brace exhibitsunstable hysteretic behaviour due to buckling in compres-sion hence it cannot dissipate much energy To avoid com-pression buckling and to achieve more energy dissipationanother brace known as buckling restrained brace (BRB) hasbeen introduced This type of brace exhibits stable hysteric
6 Shock and Vibration
0 40 80 120
Mean MCE demands Mean MCE demands
0 1 2 3minus5
0
5
10
15
20
25
30
35
40
Leve
l num
ber
minus5
0
5
10
15
20
25
30
35
40
Leve
l num
ber
Shear (kN times 103) Moment (kNmiddotm times 106)
Figure 5 Inelastic MCE shear and moment demands in the controlled structure
Encasing mortar
Yielding steel core
Steel tube
Unbonding materialbetween steel core
and mortar
Figure 6 Typical BRB
behaviour because its compression buckling is avoided due toencasing by an outer steel tubeThemain brace and outer tubeare separated by bonding material in order to accommodatethe lateral expansion due to its compression yielding [37] Atypical BRB is shown in Figure 6 [38]
52 Location of Buckling Restrained Braces BRBs have beeninstalled at several critical locations based on the results ofelastic modal decomposition analysis in dominant modessuch as 1st 2nd and 3rd modes and results are comparedwith controlled structure described in Section 4 (Option-1)In second option (Option-2) the BRBs have been installed
at bays 2 3 and 4 between peripheral columns and centralcore wall based on the maximum racking shear deformationdemands in 2nd and 3rd modes This arrangement is shownin Figure 7 In third option small size BRBs have also beeninstalled at bays 2 and 4 in cut in central core wall at the max-imum moment demands in 2nd and 3rd modes These BRBsare in addition to the BRBs in Option-2 This arrangementis shown in Figure 8 In final and fourth option (Option-4)BRBs have been installed in cut in central core wall at bays 2and 4 at the location of maximum shear force in 2nd and 3rdmodes in addition to the BRBs in Option-2 This is shownin Figure 9 It may be noted that the locations of BRBs in
Shock and Vibration 7
0
5
10
15
20
25
30
35
40
0
000
1
000
2
000
3
000
4
000
5
Leve
l
Racking shear deformation ratioMode-2Mode-3
Mode-4
Figure 7 Arrangement of the BRBs at locations of maximum racking shear deformation in exterior panels (Option-2)
0
5
10
15
20
25
30
35
40
0 1 2 3
Leve
l
0
5
10
15
20
25
30
35
40
Leve
l
Mode-2Mode-3
Mode-4 Mode-2Mode-3
Mode-4
Moment (kNmiddotm times 106)
0
000
1
000
2
000
3
000
4
000
5
Racking shear deformation ratio
Figure 8 Arrangement of the exterior BRBs at locations of maximum DBE elastic racking shear deformation in 2nd and 3rd mode andinterior BRBs at locations of maximum DBE elastic moment demands in 2nd and 3rd mode (Option-3)
8 Shock and Vibration
0
5
10
15
20
25
30
35
40Le
vel
0
5
10
15
20
25
30
35
40
0 50 100
Leve
l num
ber
Shear (kN times 103)
Mode-2Mode-3
Mode-4 Mode-2Mode-3
Mode-4
0
000
1
000
2
000
3
000
4
000
5
Racking shear deformation ratio
Figure 9 Arrangement of the exterior BRBs at locations of maximum DBE elastic racking shear deformation in 2nd and 3rd mode andinterior BRBs at locations of maximum DBE elastic shear demands in 2nd and 3rd mode (Option-3)
Option-1 Option-2 andOption-3 are also suitable for mode-1
The BRBs dissipate energy through axial tension andcompression To achieve maximum energy dissipation theBRBs should be placed at the proper locations and anglesEach BRB has been placed at an angle of approximately1205874 covering almost three stories for exterior brace and twostories for brace in cut in core wall These V-shaped BRBsconfigurations resemble the BRBs configuration used inmegabraced frames steel buildings reported in the previous studies[39ndash41] BRBs shall cross the slabs through purposely builtopenings provided in the slabs A horizontal drag elementis used from point where BRB connects to the column tothe central core wall to take care of the horizontal forcecomponent of the BRB axial force at column connection
53 Size of Buckling Restrained Braces Sizes of the BRBs havebeen selected by hit and trial using more rigorous nonlineartime history analyses (NLTHAs) using displacement-baseddesign approach Their size should neither be too large tobe uneconomical nor be too small to be ineffective The 119883-section of the braces between peripheral columns and centralcore wall is selected as 7500mm2 whereas it is 3750mm2for braces in cuts in core wall The buckling restrained bracesmanufactured by star seismic with normal yield strength of280MPa are used for braces between peripheral columnsand central core wall [42] However the low yield point-100(LYP100) steel core manufactured by Nippon Steel Corpora-tion Japan with specified yield strength of 100MPa is used
f
0DXDU
FY
FUO
FUH
KF
KO
Figure 10 Trilinear curve for BRBs
for braces in cut elements [22]The lowyield point steel bracesare used in cut in core wall to mainly achieve more energydissipation through the early yielding of the brace [43]
54 Modelling of Buckling Restrained Braces A BRB consistsof three components that is central yielding core brace endsmember connecting the central brace with the pin connec-tion and pin connection between brace and main structuralmembers The length of the exterior core brace is 45mwhereas length of the core brace in cut of core wall is 18mThese lengths are in the optimum range of 02ndash04 times thetotal length of the brace Several advantages such as simple
Shock and Vibration 9
minus4000
minus3000
minus2000
minus1000
0
1000
2000
3000
4000A
xial
forc
e ( k
N)
Axial def (m)
10E minus 0150E minus 0200E + 00minus50E minus 02
(a)
minus500
minus400
minus300
minus200
minus100
0
100
200
300
400
500
Axi
al fo
rce (
kN
)
Axial def (m)
20E
minus03
10E
minus03
00E
+00
minus30E
minus03
minus20E
minus03
minus10E
minus03
(b)
Figure 11 Typical cyclic response of BRBs obtained from the analysis (a) Exterior brace (b) interior brace
replacement lesser weight concrete elimination economyand easy erection process are associated with reduced lengthof the core brace [44ndash50] BRB has been modelled using theBRB compound component of the Perform-3D Such mem-ber is composed of three components that is (1) a BRB basiccomponent for main yielding brace (2) an elastic bar basiccomponent for member connecting brace with gusset plateand (3) a stiff end zone which accounts for the gusset platesand so forth at both ends of the member
The positive side (tension) of the trilinear curve to definethe force-deformation of the BRBs is shown in Figure 10 Itcan be seen that after yielding there are two lines such asbottom and top line The bottom line is used to simulate firstcyclic load and the top line is used to simulate full strainhardening The same behavior has been observed in testslike the hysteresis loop which can progressively grow in sizeThis is sometimes referred to as ldquoisotropic hardeningrdquo Thisleads to the component increase in strength under cyclic loadThe negative side of the curve shows a little variation due todifference in the values of compression and tensions FY FUO(FUO (T) = 105 FY FUO (C) = 104 FY) and FUH (FUO(T) = 134 FY FUO (C) = 151 FY) are yield strength strengthat first loading cycle and strength of the core brace afterfull hardening respectively DU (DU (T) = 07 DU (C) =07) is the deformation at FUO and DX (DX (T) = 004 LYCDX (C) = 004 LYC) is the maximum deformation of thebrace LYC is the length of the yielding core KO is theInitial stiffness of the core brace and KF (= 002KO) is theslope of third line [42] The strain hardening properties suchas deformation at FUO-FUH average are taken equal to 2times (LYC180) and deformation at FUH is taken as 35times (LYC180) The typical force-deformation relationshipfor exterior (between peripheral columns and core wall) andinterior BRB (in cut in core wall) obtained from NLRHAanalysis for a particular ground motion is shown in Figures11(a) and 11(b) respectivelyThese figures show that hysteresisloop is similar to the reported Clark et al 1999 [38] provingthat performing BRB element can capture the behaviour
appropriately The size of the elastic bar element is selectedsuch that it can safely carry maximum axial force in brace inelastic range to conform to the capacity design approach Stiffend zone is few times stiffer than the elastic bar element
6 Comparison of the Responses in DifferentOptions and Discussion on the Results
NLRHA is performed using seven spectrally matched timehistories Different response quantities such as displacementplastic hinge rotations in coupling beams and core wall sheardeformation angle (story racking shear deformation) bend-ing moment shear force and energy demands are obtainedfrom this analysisThe plastic rotations are calculated bymul-tiplying the average curvature of the wall at mid height withthe plastic hinge length The mean value of different quan-tities obtained from seven ground motions are shown anddiscussed in following paragraphs
Shear demands obtained from four options are shownin Figure 12(a) Shear demand pattern and magnitude aresimilar in all options Moment demands obtained from fouroptions are shown in Figure 12(b) The moment demand atthe base is similar in all four options because this is clippedto the flexural strength of the plastic hinge at the base of thewall However it is reduced along the wall height by 30 35and 40 in Option-2 Option-3 and Option-4 respectivelyin comparison to that in 1st optionThe reduction inmomentdemand is significant in all options This will help to avoidreinforcement congestion in the wall near mid height
Displacement demands obtained from four options areshown in Figure 13(a) Displacement demand pattern is simi-lar for all options However displacement demand is reducedalong thewall height by 40 40 and 60 inOption-2 Option-3 and Option-4 respectively in comparison to that in 1stoption Racking shear deformation demands obtained fromfour options are shown in Figure 13(b) The racking sheardeformation demand patterns are similar for all four optionsHowever racking shear deformation demands are reduced
10 Shock and Vibration
minus5
0
5
10
15
20
25
30
35
40
0 50000 100000 150000
Leve
l
Shear force (kN)
Option-1Option-2
Option-3Option-4
(a)
minus5
0
5
10
15
20
25
30
35
40
Leve
l
0 1 2 3
Option-1Option-2
Option-3Option-4
Bending moment (kNmiddotm times 106)
(b)
Figure 12 MCE inelastic shear and moment demands in different options (a) Shear (b) moment
0 05 1 15 2 25Displacement (m)minus5
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(a)
0 001 002 003 004Racking shear deformation ratio
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(b)
Figure 13 MCE inelastic displacement and racking deformation demands in different options (a) Displacement (b) racking sheardeformation angle
along the wall height by 40 40 and 65 in Option-2Option-3 and Option-4 respectively in comparison to thatin 1st option This is significant reduction Racking sheardeformations of 0036 in the controlled structures are reducedto 0023 which is well within the limit of 003 set by [29]LATBSDC 2008 for the MCE level earthquake
Rotational demands in the core wall at the base level aswell as in coupling beams along the height are shown in Fig-ures 14(a) and 14(b) respectivelyThe rotation demand in thewall is calculated by multiplying the average curvature at themid height of the inelastic wall element by height of the wallThe comparison shows that themaximum rotational demand
at the base of the wall is reduced by 99 57 and 93 inOption-2Option-3 andOption-4 respectively in comparison to thatin 1st option This is strong indication that damage at thebase of the wall shall be reduced to half and consequentlyextent of repair shall be small and hence cheap in case ofsevere MCE events such as DBE and MCE level earthquakeThe rotational demands in coupling beams are reduced by52 40 and 35 respectively above the half height level forOption-2 Option-3 and Option-4 respectively in compar-ison to 1st option However rotation demand remained thesame in the lower half portion of the building for all options
Energy dissipated by core wall coupling beams andbuckling restrained braces have been compared in Figures15(a)ndash15(d) respectively for Option-1 Option-2 Option-3 and Option-4 respectively This is energy dissipated inpercentage of the total energy demand in the structure Thetotal energy demand is sum of the kinetic energy elasticstrain energy energy dissipated by elastic modal dampingand energy dissipation by damage in structural elements suchas core wall coupling beams and BRBs About 83 9292 and 90 energy have been dissipated by elastic modaland inelastic damping in Option-1 to Option-4 respectivelyThe energy dissipation by modal elastic damping to the totalenergy demands is 50 37 35 and 33 respectively inOption-1 to Option-4 respectivelyThe energy dissipation bycore wall at the base to the total energy demands is 22 66 and 6 inOption-1 to Option-4 respectivelyThe energydissipation by coupling beams to the total energy demands isapproximately 10 4 5 and 6 in Option-1 to Option-4 respectively The energy dissipation by BRBs to the total
energy demands is 0 45 45 and 45 respectively inOption-1 to Option-4
7 Effects of BRBs on Axial Loads Shearand Moment of Columns and PermanentDeformation due to BRBs Plastification
Effects of BRBs on axial loads of columns and permanentdeformation due to BRBs plastification have been discussedin this section The axial load envelope in a typical columnfor Options-1ndash4 is shown in the Figure 16 The magnitude ofaxial load is same for Options-2ndash4 (with BRBs) and is twicethan that in Option-1 (controlled structure) This is due tothe outrigger effect created by the connection of columnsand core wall through BRBs Some core wall moment hasbeen resisted by the development of axial push-pull in thecolumns Furthermore the shape of the axial load envelopeis smooth in case of Option-1 whereas it is jagged at thelocations of the BRBs forOptions-2ndash4Themoment envelopeand shear envelope for one typical column are shown inFigures 17(a) and 17(b) respectively It shows that momentand shear have been reduced at the ground level in Options-2ndash4 in comparison to Option-1 whereas these remain almostthe same at upper portions The extra moment and shearat the ground level in Options-1ndash4 is due to the transfer ofmoment and shear to the columns when core wall yields
To better understand the permanent deformation in thestructure due to BRBs plastification cyclic pushover analysisin firstmode is performedusing target displacement obtainedfrom NLTHA for all cases The cyclic base shear versus top
12 Shock and Vibration
Option-1
0
20
40
60
80
100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 53478kNmiddotm
(a)
Option-2
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 73328kNmiddotm
(b)
Option-3
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80 90
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 71449kNmiddotm
(c)
Option-4
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 69558kNmiddotm
(d)
Figure 15 Inelastic energy demands in structural components (a) to (d) For Option-1 to Option-4 respectively
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus20000 minus10000 0
Leve
l
Axial load (kN)
Option-1Option-2
Option-3Option-4
Figure 16 Axial load envelope in one typical column
Shock and Vibration 13
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus15000 0 15000 30000
Leve
l
minus5
0
5
10
15
20
25
30
35
40
Leve
l
Moment (kNmiddotm)
minus1200 minus800 minus400 0 400 800 1200
Shear (kN)
Option-1Option-2
Option-3Option-4
Option-1Option-2
Option-3Option-4
Figure 17 Moment and shear envelope in one typical column
minus20 minus10 00 10 20
Base
shea
r (kN
)
Top displacement (m)
Option-1Option-2
Option-3Option-4
300E + 04
200E + 04
100E + 04
000E + 00
minus100E + 04
minus200E + 04
minus300E + 04
Figure 18 Base shear versus top displacement relationship in firstmode load pattern
displacement is compared in Figure 18 It can be seen that thiscurve is flag shaped for Option-1 whereas it is bilinear pinch-ing type in Options-2ndash4There is no permanent deformationin controlled structure and flag shaped hysteresis behaviouris observed The same behaviour was observed during testconducted on a large-scale model of a concrete shear wallfrom the core of a high-rise building in the study of Adebar etal [27] The combination of low percentage of vertical rein-forcement and large axial compression force due to gravity
loads (axial force(concrete 28 days cylinder strength times grossarea ofwall)gt 01) caused the flexural cracks to closewhen thelateral load was removed In Options-2ndash4 small permanentdeformation (residual displacement) is observed This isbecause of the plastification of BRBs as well as transfer of themoment demand from shear wall to columns in the form ofaxial push-pull
8 Conclusions
(i) In this study different options of location of BRBsare investigated for a 40-story case study buildingThe locations of BRBs are identified based on theDBE elastic racking shear deformation and shear andbending moment demands in dominant 2nd and 3rdmodes NLRHA is then performed for seven sets ofspectrally matched target time histories and resultsare compared for different options
(ii) In all options shear force demands bending momentat mid height displacement demand racking sheardeformation demand and rotation demand in cou-pling beams are reduced by 10 45 45 45 and40 respectively in comparison to the controlledstructure
(iii) Rotational demand in the core wall at base level isreduced by 99 57 and 93 in Option-2 Option-3 and Option-4 respectively in comparison toOption-1Whereas energy dissipated by the core wallis reduced by around 250 in the corewall in compar-ison to the controlled structure Rotational demandand energy dissipation are measure of damage in thecore wall Thus damage can be significantly reducedby installation of BRBs
14 Shock and Vibration
(iv) All BRBs options are effective for bending momentreduction at mid height displacement and rackingshear deformation demands along the wall heightand rotation demand at the base of the wall and incoupling beams above the mid height of the build-ing However Option-4 in which BRBs are installedbetween peripheral columns and central corewall andcut in shear walls based on the maximum shear forceand bending moment leads to the highest reductionThis is because of the early yielding of the interiorbraces
(v) Thiswork is equally important for academia and prac-tising engineers especially those working in the fieldof performance based design of the high-rise build-ings in the commercial consultancy This will helpthem to locate BRBs at appropriate locations whiledesigning their buildings in an optimal way
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] International Conference of Building Officials Uniform Build-ing Code vol 2 International Conference of Building OfficialsWhittier Calif USA 1997
[2] J Maffei and N Yuen ldquoSeismic performance and designrequirements for high rise buildingsrdquo Structural Magazine pp28ndash32 2007
[3] J P Moehle ldquoPerformance-based seismic design of tall build-ings in the USrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[4] CEN EC8 Design of Structures for Earthquake ResistanceEuropean Committee for Standardization Brussels Belgium2004
[5] NZS 3101 Part 12006 Concrete Structures Standards NewZealand Standards New Zealand Wellington New Zealand2006
[6] T Paulay and M J N Priestley Seismic Design of ReinforcedConcrete and Masonry Buildings Wiley Hoboken NJ USA1992
[7] M Panagiotou J I Restrepo and J P Conte ldquoShake table test ofa 7-story full scale reinforced concrete structural wall buildingslice phase I rectangular wallrdquo Report SSRP 07-07 Departmentof Structural Engineering University of California San DiegoSan Diego Calif USA 2007
[8] Canadian Standard Association CSA Standard A233-04Design of Concrete Structures Canadian Standard AssociationRexdale Canada 2005
[9] R Klemencic J A Fry J D Hooper and B G MorgenldquoPerformance-based design of ductile concrete core wall build-ingsmdashissues to consider before detailed analysisrdquoTheStructuralDesign of Tall and Special Buildings vol 16 no 5 pp 599ndash6142007
[10] R Klemencic ldquoPerformance based seismic designmdashrisingrdquoStructural Magazine 2008 httpwwwstructuremagorgwp-contentuploads201408C-StructuralPractices-Klemencic-June081pdf
[11] A Zekioglu M Willford L Jin and M Melek ldquoCase studyusing the Los Angeles tall buildings structural design councilguidelines 40-storey concrete core wall buildingrdquo StructuralDesign of Tall and Special Buildings vol 16 no 5 pp 583ndash5972007
[12] B R Rad and P Adebar ldquoDynamic shear amplification inhigh-rise concrete walls effect of multiple flexural hinges andshear crackingrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[13] M Panagiotou and J I Restrepo ldquoDual-plastic hinge designconcept for reducing higher-mode effects on high-rise can-tilever wall buildingsrdquo Earthquake Engineering and StructuralDynamics vol 38 no 12 pp 1359ndash1380 2009
[14] M Ahmed and P Warnitchai ldquoReduction of inelastic seismicdemands by inducing plastic hinges at effective locationsrdquoin Proceedings of the 3rd Asian Conference on EarthquakeEngineering (ACEE rsquo10) Bangkok Thailand December 2010
[15] A Munir and P Warnitchai ldquoThe cause of unproportion-ately large higher mode contributions in the inelastic seismicresponses of high-rise core-wall buildingsrdquo Earthquake Engi-neering amp Structural Dynamics vol 41 no 15 pp 2195ndash22142012
[16] A Munir and P Warnitchai ldquoOptimal reduction of inelasticseismic demands in high-rise reinforced concrete core wallbuildings using energy-dissipating devicesrdquo Structural Design ofTall and Special Buildings vol 22 no 7 pp 543ndash568 2013
[17] M C Constantinou and M D Symans ldquoExperimental andanalytical investigation of seismic response of structures withsupplemental fluid viscous dampersrdquo NCEER Reports 92-0032State University of New York at Buffalo Buffalo NY USA 1992
[18] A SWhittaker V V Bertero C LThompson and L J AlonsoldquoSeismic testing of steel plate energy dissipation devicesrdquoEarthquake Spectra vol 7 no 4 pp 563ndash604 1991
[19] G W Housner L A Bergman T K Caughey et al ldquoStruc-tural control past present and futurerdquo Journal of EngineeringMechanics vol 123 no 9 pp 897ndash971 1997
[20] M D Symans F A Charney A S Whittaker et al ldquoEnergydissipation systems for seismic applications current practiceand recent developmentsrdquo Journal of Structural Engineering vol134 no 1 pp 3ndash21 2008
[21] C J Black N Makris and I D Aiken ldquoComponent testingseismic evaluation and characterization of buckling-restrainedbracesrdquo Journal of Structural Engineering vol 130 no 6 pp880ndash894 2004
[22] S Keten A performance based approach for seismic designwith hysteretic dampers [MS thesis] Massachusetts Institute ofTechnology (MIT) 2006 httpdspacemitedubitstreamhan-dle172113459571252112-MITpdfsequence=2
[23] N Anwar J A Sy T H Aung and D Rayamajhi ldquoFirstapplication of buckling restraint brace system in Philippines ina 50-story building with ductile core wall and PT slab systemrdquoin Proceedings of the 9th International Conference on UrbanEarthquake Engineering and the 4th Asia Conference on Earth-quake Engineering Tokyo Institute of Technology Tokyo JapanMarch 2012
[24] Computers and Structures Inc ETABS Extended 3D Analysis ofBuilding Systems Software Nonlinear Version 900 Computersand Structures Inc Berkeley Calif USA 2005
[25] Computers and Structures Perform 3D Nonlinear Analysis andPerformance Assessment for 3D Structures User Guide Version 4Computers and Structures Berkeley Calif USA 2006
Shock and Vibration 15
[26] J W Wallace and J P Moehle ldquoDuctility and detailing require-ments of bearing wall buildingsrdquo Journal of Structural Engineer-ing vol 118 no 6 pp 1625ndash1644 1992
[27] P Adebar A M M Ibrahim and M Bryson ldquoTest of high-risecore wall effective stiffness for seismic analysisrdquo ACI StructuralJournal vol 104 no 5 pp 549ndash559 2007
[28] FEMA ldquoPrestandard and commentary for the seismic rehabil-itation of buildingsrdquo FEMA 356 Federal Emergency Manage-ment Agency Washington DC USA 2000
[29] LATBDSC An Alternative Procedure for Seismic Analysis andDesign of Tall Buildings Located in Los Angeles Region A Con-sensus Document Los Angeles Tall Buildings and StructuralDesign Council 2008
[30] PEERNGAData Base Pacific Earthquake Engineering Research(PEER) University of California Berkeley Calif USA 2005httppeerberkeleyedunga
[31] COSMOS Data Base ldquoConsortium of organization for strong-motion observation systemsrdquo Tech Rep University of Cali-fornia Berkeley Calif USA 1999ndash2007 httpwwwcosmos-eqorgscriptsdefaultplx
[32] K Lilhanand and W S Tseng ldquoDevelopment and applicationof realistic earthquake time histories compatible with multipledamping design spectrardquo in Proceedings of the 9th World Con-ference on Earthquake Engineering Tokyo Japan August 1988
[33] J Hancock J Watson-Lamprey N A Abrahamson et al ldquoAnimproved method of matching response spectra of recordedearthquake ground motion using waveletsrdquo Journal of Earth-quake Engineering vol 10 no 1 pp 67ndash89 2006
[34] J B Mander M J N Priestley and R Park ldquoTheoreticalstress-strain model for confined concreterdquo Journal of StructuralEngineering New York vol 114 no 8 pp 1804ndash1826 1988
[35] CTBUH Seismic Working Group CTBUH Recommendationsfor the Seismic Design of High-Rise Buildings A ConsensusDocument 2008
[36] N Satake K-I Suda T Arakawa A Sasaki and Y TamuraldquoDamping evaluation using full-scale data of buildings inJapanrdquo Journal of Structural Engineering vol 129 no 4 pp 470ndash477 2003
[37] Q Xie ldquoState of the art of buckling-restrained braces in AsiardquoJournal of Constructional Steel Research vol 61 no 6 pp 727ndash748 2005
[38] P Clark K Kasai I Aiken E Ko and I Kimura ldquoDesign proce-dures for buildings incorporating hysteretic energy dissipatingdevicesrdquo in Proceedings of the 68th Annual Convention Struc-tural Engineers Association of California Santa Barbara CalifUSA October 1999
[39] D Vafaei and R Eskandari ldquoSeismic response of mega buck-ling-restrained braces subjected to fling-step and forward-directivity near-fault ground motionsrdquo Structural Design of Talland Special Buildings vol 24 no 9 pp 672ndash686 2015
[40] L Di Sarno and A S Elnashai ldquoBracing systems for seismicretrofitting of steel framesrdquo Journal of Constructional SteelResearch vol 65 no 2 pp 452ndash465 2009
[41] A Dutta and R O Hamburger ldquoCase study of A 40-Storeybuckling-restrained braced frame building located in LosAnge-lesrdquo The Structural Design of Tall and Special Buildings vol 19no 1-2 pp 77ndash93 2010
[42] Rutherford amp Chekene ldquoPerform nonlinear component mod-elling of star seismic powercat BRBsrdquo Report to Star SeismicLLC Star Seismic LLC 2011
[43] P Dusicka A M Itani and I G Buckle ldquoCyclic response ofplate steels under large inelastic strainsrdquo Journal of Construc-tional Steel Research vol 63 no 2 pp 156ndash164 2007
[44] S A Razavi M E Shemshadian S R Mirghaderi and SAhlehagh ldquoSeismic design of buckling restrained braced frameswith reduced core lengthrdquo in Proceedings of the The StructuralEngineers World Congress Cernobbio Italy 2011
[45] S A Razavi S R Mirghaderi A Hosseini and M EShemshadian ldquoReduced length buckling restrained brace usingsteel plates as restraining segmentrdquo in Proceedings of the 15thWorld Conference on Earthquake Engineering Lisboa PurtagalSeptember 2012
[46] M E Shemshadian S A Razavi S R Mirghaderi A Hosseiniand M K Mohammadi ldquoThe advantages of reducing thelength of yielding segment in seismic performance of bucklingrestrained braced framesrdquo inProceedings of the 6th InternationalConference of Seismology and Earthquake Engineering TehranIran 2011
[47] N Ma B Wu J Zhao H Li J Ou andW Yang ldquoFull scale testof all-steel buckling restrained bracesrdquo in Proceedings of the 14thWorld Conference on Earthquake Engineering Beijing ChinaOctober 2008
[48] L Di Sarno and G Manfredi ldquoSeismic retrofitting of existingRC frames with buckling restrained bracesrdquo in Proceedings ofthe Improving the Seismic Performance of Existing Buildingsand Other Structures pp 741ndash752 San Francisco Calif USADecember 2009
[49] S Ahlehagh Improvement of the special concentrically bracedsteel frames behaviour by employing balanced braces [MSthesis] University of Tehran Tehran Iran 2008
[50] R Tremblay P Bolduc R Neville and R DeVall ldquoSeismic test-ing and performance of buckling-restrained bracing systemsrdquoCanadian Journal of Civil Engineering vol 33 no 2 pp 183ndash1982006
Unloading and reloading arethe same in case of tension
Steel material Concrete material
Mander envelopePerform-3D UnloadingReloading
f998400cc
Eo
EoEo
dcEo
120585998400cc120585998400c120585cu
ft
fu
fy
Park envelopePerform-3D Cyclic
120585y 120585sh 120585u
fy rebar yield stressfu rebar ultimate stress capacity120585y rebar yield strain120585sh strain in rebar at the onset of strain hardening120585y rebar ultimate strain capacityEo modulus of elasticiy
f998400c compressive strength of unconfined concrete
f998400cc compressive strength of confined concrete
120585998400c concrete strain atf998400c
120585998400cc concrete strain atf998400cc
120585cu ultimate strain capacity for confined concreteEo tangent modulus of elasticitydc energy dissipation factor for the reloading stiffnessft tensile strength of concrete = 75radicf998400
c (f998400c is in psi)
Figure 4 Nonlinear Park Steel and Manderrsquos concrete model
used for modelling plastic hinges at the ends of couplingbeams All slabs and columns aremodelled by elastic slab andcolumn elements of the Perform-3D respectively
Seven set of ground motions are selected from PEER[30] and COSMOS [31] data bases The ground motionsinclude both short distance moderate and long distancelarge magnitude earthquake The selected ground motionsare first roughly scaled up or down by a constant factor toapproximately match the target MCE spectrum The roughlyscaled ground motions are then matched to the MCE targetspectrum by using time domain spectral matching techniqueof [32] The software RSP match [33] is used for this purposeThe target spectrum and spectra of seven spectrally matchedtime history used in this study are shown in Figure 2 Non-linearmaterial models similar to those proposed by [34] wereassigned for rebarrsquos and concrete material respectively asshown in Figure 4 The modal damping is set as per recom-mendations of [35] CTBUH (2008) and [36]
4 Analysis of Structure without BRBs
The controlled structure described in Section 3 is analysedfor seven sets of ground motions The shear and momentdemands obtained are shown in Figure 5 These results showthat base shear demand is about 15 of the total building
weight Similarly moment demand is also very high at midheight However at the base the moment demand is clippedto the flexural strength of plastic hinge If the wall is designedfor mid height moment to remain elastic and hence nodamage there shall be reinforcement congestion On theother hand if plastic hinge is allowed at mid height the corewall shall be subjected to high rotational demands and hencedamage near themid height of thewall in addition to the baseTo reduce damage at the base of the wall as well as reducemid height moment to avoid reinforcement congestion analternative strategy using different arrangements of buck-ling restrained braces (energy dissipating devices) has beenevolved in the next section (Options-2ndash4) and results arecompared with the controlled structure (Option-1)
5 Buckling Restrained Braces Evolvement ofStrategies for Efficient Locations Their Sizeand Modelling
51 Buckling Restrained Brace An ordinary brace exhibitsunstable hysteretic behaviour due to buckling in compres-sion hence it cannot dissipate much energy To avoid com-pression buckling and to achieve more energy dissipationanother brace known as buckling restrained brace (BRB) hasbeen introduced This type of brace exhibits stable hysteric
6 Shock and Vibration
0 40 80 120
Mean MCE demands Mean MCE demands
0 1 2 3minus5
0
5
10
15
20
25
30
35
40
Leve
l num
ber
minus5
0
5
10
15
20
25
30
35
40
Leve
l num
ber
Shear (kN times 103) Moment (kNmiddotm times 106)
Figure 5 Inelastic MCE shear and moment demands in the controlled structure
Encasing mortar
Yielding steel core
Steel tube
Unbonding materialbetween steel core
and mortar
Figure 6 Typical BRB
behaviour because its compression buckling is avoided due toencasing by an outer steel tubeThemain brace and outer tubeare separated by bonding material in order to accommodatethe lateral expansion due to its compression yielding [37] Atypical BRB is shown in Figure 6 [38]
52 Location of Buckling Restrained Braces BRBs have beeninstalled at several critical locations based on the results ofelastic modal decomposition analysis in dominant modessuch as 1st 2nd and 3rd modes and results are comparedwith controlled structure described in Section 4 (Option-1)In second option (Option-2) the BRBs have been installed
at bays 2 3 and 4 between peripheral columns and centralcore wall based on the maximum racking shear deformationdemands in 2nd and 3rd modes This arrangement is shownin Figure 7 In third option small size BRBs have also beeninstalled at bays 2 and 4 in cut in central core wall at the max-imum moment demands in 2nd and 3rd modes These BRBsare in addition to the BRBs in Option-2 This arrangementis shown in Figure 8 In final and fourth option (Option-4)BRBs have been installed in cut in central core wall at bays 2and 4 at the location of maximum shear force in 2nd and 3rdmodes in addition to the BRBs in Option-2 This is shownin Figure 9 It may be noted that the locations of BRBs in
Shock and Vibration 7
0
5
10
15
20
25
30
35
40
0
000
1
000
2
000
3
000
4
000
5
Leve
l
Racking shear deformation ratioMode-2Mode-3
Mode-4
Figure 7 Arrangement of the BRBs at locations of maximum racking shear deformation in exterior panels (Option-2)
0
5
10
15
20
25
30
35
40
0 1 2 3
Leve
l
0
5
10
15
20
25
30
35
40
Leve
l
Mode-2Mode-3
Mode-4 Mode-2Mode-3
Mode-4
Moment (kNmiddotm times 106)
0
000
1
000
2
000
3
000
4
000
5
Racking shear deformation ratio
Figure 8 Arrangement of the exterior BRBs at locations of maximum DBE elastic racking shear deformation in 2nd and 3rd mode andinterior BRBs at locations of maximum DBE elastic moment demands in 2nd and 3rd mode (Option-3)
8 Shock and Vibration
0
5
10
15
20
25
30
35
40Le
vel
0
5
10
15
20
25
30
35
40
0 50 100
Leve
l num
ber
Shear (kN times 103)
Mode-2Mode-3
Mode-4 Mode-2Mode-3
Mode-4
0
000
1
000
2
000
3
000
4
000
5
Racking shear deformation ratio
Figure 9 Arrangement of the exterior BRBs at locations of maximum DBE elastic racking shear deformation in 2nd and 3rd mode andinterior BRBs at locations of maximum DBE elastic shear demands in 2nd and 3rd mode (Option-3)
Option-1 Option-2 andOption-3 are also suitable for mode-1
The BRBs dissipate energy through axial tension andcompression To achieve maximum energy dissipation theBRBs should be placed at the proper locations and anglesEach BRB has been placed at an angle of approximately1205874 covering almost three stories for exterior brace and twostories for brace in cut in core wall These V-shaped BRBsconfigurations resemble the BRBs configuration used inmegabraced frames steel buildings reported in the previous studies[39ndash41] BRBs shall cross the slabs through purposely builtopenings provided in the slabs A horizontal drag elementis used from point where BRB connects to the column tothe central core wall to take care of the horizontal forcecomponent of the BRB axial force at column connection
53 Size of Buckling Restrained Braces Sizes of the BRBs havebeen selected by hit and trial using more rigorous nonlineartime history analyses (NLTHAs) using displacement-baseddesign approach Their size should neither be too large tobe uneconomical nor be too small to be ineffective The 119883-section of the braces between peripheral columns and centralcore wall is selected as 7500mm2 whereas it is 3750mm2for braces in cuts in core wall The buckling restrained bracesmanufactured by star seismic with normal yield strength of280MPa are used for braces between peripheral columnsand central core wall [42] However the low yield point-100(LYP100) steel core manufactured by Nippon Steel Corpora-tion Japan with specified yield strength of 100MPa is used
f
0DXDU
FY
FUO
FUH
KF
KO
Figure 10 Trilinear curve for BRBs
for braces in cut elements [22]The lowyield point steel bracesare used in cut in core wall to mainly achieve more energydissipation through the early yielding of the brace [43]
54 Modelling of Buckling Restrained Braces A BRB consistsof three components that is central yielding core brace endsmember connecting the central brace with the pin connec-tion and pin connection between brace and main structuralmembers The length of the exterior core brace is 45mwhereas length of the core brace in cut of core wall is 18mThese lengths are in the optimum range of 02ndash04 times thetotal length of the brace Several advantages such as simple
Shock and Vibration 9
minus4000
minus3000
minus2000
minus1000
0
1000
2000
3000
4000A
xial
forc
e ( k
N)
Axial def (m)
10E minus 0150E minus 0200E + 00minus50E minus 02
(a)
minus500
minus400
minus300
minus200
minus100
0
100
200
300
400
500
Axi
al fo
rce (
kN
)
Axial def (m)
20E
minus03
10E
minus03
00E
+00
minus30E
minus03
minus20E
minus03
minus10E
minus03
(b)
Figure 11 Typical cyclic response of BRBs obtained from the analysis (a) Exterior brace (b) interior brace
replacement lesser weight concrete elimination economyand easy erection process are associated with reduced lengthof the core brace [44ndash50] BRB has been modelled using theBRB compound component of the Perform-3D Such mem-ber is composed of three components that is (1) a BRB basiccomponent for main yielding brace (2) an elastic bar basiccomponent for member connecting brace with gusset plateand (3) a stiff end zone which accounts for the gusset platesand so forth at both ends of the member
The positive side (tension) of the trilinear curve to definethe force-deformation of the BRBs is shown in Figure 10 Itcan be seen that after yielding there are two lines such asbottom and top line The bottom line is used to simulate firstcyclic load and the top line is used to simulate full strainhardening The same behavior has been observed in testslike the hysteresis loop which can progressively grow in sizeThis is sometimes referred to as ldquoisotropic hardeningrdquo Thisleads to the component increase in strength under cyclic loadThe negative side of the curve shows a little variation due todifference in the values of compression and tensions FY FUO(FUO (T) = 105 FY FUO (C) = 104 FY) and FUH (FUO(T) = 134 FY FUO (C) = 151 FY) are yield strength strengthat first loading cycle and strength of the core brace afterfull hardening respectively DU (DU (T) = 07 DU (C) =07) is the deformation at FUO and DX (DX (T) = 004 LYCDX (C) = 004 LYC) is the maximum deformation of thebrace LYC is the length of the yielding core KO is theInitial stiffness of the core brace and KF (= 002KO) is theslope of third line [42] The strain hardening properties suchas deformation at FUO-FUH average are taken equal to 2times (LYC180) and deformation at FUH is taken as 35times (LYC180) The typical force-deformation relationshipfor exterior (between peripheral columns and core wall) andinterior BRB (in cut in core wall) obtained from NLRHAanalysis for a particular ground motion is shown in Figures11(a) and 11(b) respectivelyThese figures show that hysteresisloop is similar to the reported Clark et al 1999 [38] provingthat performing BRB element can capture the behaviour
appropriately The size of the elastic bar element is selectedsuch that it can safely carry maximum axial force in brace inelastic range to conform to the capacity design approach Stiffend zone is few times stiffer than the elastic bar element
6 Comparison of the Responses in DifferentOptions and Discussion on the Results
NLRHA is performed using seven spectrally matched timehistories Different response quantities such as displacementplastic hinge rotations in coupling beams and core wall sheardeformation angle (story racking shear deformation) bend-ing moment shear force and energy demands are obtainedfrom this analysisThe plastic rotations are calculated bymul-tiplying the average curvature of the wall at mid height withthe plastic hinge length The mean value of different quan-tities obtained from seven ground motions are shown anddiscussed in following paragraphs
Shear demands obtained from four options are shownin Figure 12(a) Shear demand pattern and magnitude aresimilar in all options Moment demands obtained from fouroptions are shown in Figure 12(b) The moment demand atthe base is similar in all four options because this is clippedto the flexural strength of the plastic hinge at the base of thewall However it is reduced along the wall height by 30 35and 40 in Option-2 Option-3 and Option-4 respectivelyin comparison to that in 1st optionThe reduction inmomentdemand is significant in all options This will help to avoidreinforcement congestion in the wall near mid height
Displacement demands obtained from four options areshown in Figure 13(a) Displacement demand pattern is simi-lar for all options However displacement demand is reducedalong thewall height by 40 40 and 60 inOption-2 Option-3 and Option-4 respectively in comparison to that in 1stoption Racking shear deformation demands obtained fromfour options are shown in Figure 13(b) The racking sheardeformation demand patterns are similar for all four optionsHowever racking shear deformation demands are reduced
10 Shock and Vibration
minus5
0
5
10
15
20
25
30
35
40
0 50000 100000 150000
Leve
l
Shear force (kN)
Option-1Option-2
Option-3Option-4
(a)
minus5
0
5
10
15
20
25
30
35
40
Leve
l
0 1 2 3
Option-1Option-2
Option-3Option-4
Bending moment (kNmiddotm times 106)
(b)
Figure 12 MCE inelastic shear and moment demands in different options (a) Shear (b) moment
0 05 1 15 2 25Displacement (m)minus5
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(a)
0 001 002 003 004Racking shear deformation ratio
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(b)
Figure 13 MCE inelastic displacement and racking deformation demands in different options (a) Displacement (b) racking sheardeformation angle
along the wall height by 40 40 and 65 in Option-2Option-3 and Option-4 respectively in comparison to thatin 1st option This is significant reduction Racking sheardeformations of 0036 in the controlled structures are reducedto 0023 which is well within the limit of 003 set by [29]LATBSDC 2008 for the MCE level earthquake
Rotational demands in the core wall at the base level aswell as in coupling beams along the height are shown in Fig-ures 14(a) and 14(b) respectivelyThe rotation demand in thewall is calculated by multiplying the average curvature at themid height of the inelastic wall element by height of the wallThe comparison shows that themaximum rotational demand
at the base of the wall is reduced by 99 57 and 93 inOption-2Option-3 andOption-4 respectively in comparison to thatin 1st option This is strong indication that damage at thebase of the wall shall be reduced to half and consequentlyextent of repair shall be small and hence cheap in case ofsevere MCE events such as DBE and MCE level earthquakeThe rotational demands in coupling beams are reduced by52 40 and 35 respectively above the half height level forOption-2 Option-3 and Option-4 respectively in compar-ison to 1st option However rotation demand remained thesame in the lower half portion of the building for all options
Energy dissipated by core wall coupling beams andbuckling restrained braces have been compared in Figures15(a)ndash15(d) respectively for Option-1 Option-2 Option-3 and Option-4 respectively This is energy dissipated inpercentage of the total energy demand in the structure Thetotal energy demand is sum of the kinetic energy elasticstrain energy energy dissipated by elastic modal dampingand energy dissipation by damage in structural elements suchas core wall coupling beams and BRBs About 83 9292 and 90 energy have been dissipated by elastic modaland inelastic damping in Option-1 to Option-4 respectivelyThe energy dissipation by modal elastic damping to the totalenergy demands is 50 37 35 and 33 respectively inOption-1 to Option-4 respectivelyThe energy dissipation bycore wall at the base to the total energy demands is 22 66 and 6 inOption-1 to Option-4 respectivelyThe energydissipation by coupling beams to the total energy demands isapproximately 10 4 5 and 6 in Option-1 to Option-4 respectively The energy dissipation by BRBs to the total
energy demands is 0 45 45 and 45 respectively inOption-1 to Option-4
7 Effects of BRBs on Axial Loads Shearand Moment of Columns and PermanentDeformation due to BRBs Plastification
Effects of BRBs on axial loads of columns and permanentdeformation due to BRBs plastification have been discussedin this section The axial load envelope in a typical columnfor Options-1ndash4 is shown in the Figure 16 The magnitude ofaxial load is same for Options-2ndash4 (with BRBs) and is twicethan that in Option-1 (controlled structure) This is due tothe outrigger effect created by the connection of columnsand core wall through BRBs Some core wall moment hasbeen resisted by the development of axial push-pull in thecolumns Furthermore the shape of the axial load envelopeis smooth in case of Option-1 whereas it is jagged at thelocations of the BRBs forOptions-2ndash4Themoment envelopeand shear envelope for one typical column are shown inFigures 17(a) and 17(b) respectively It shows that momentand shear have been reduced at the ground level in Options-2ndash4 in comparison to Option-1 whereas these remain almostthe same at upper portions The extra moment and shearat the ground level in Options-1ndash4 is due to the transfer ofmoment and shear to the columns when core wall yields
To better understand the permanent deformation in thestructure due to BRBs plastification cyclic pushover analysisin firstmode is performedusing target displacement obtainedfrom NLTHA for all cases The cyclic base shear versus top
12 Shock and Vibration
Option-1
0
20
40
60
80
100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 53478kNmiddotm
(a)
Option-2
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 73328kNmiddotm
(b)
Option-3
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80 90
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 71449kNmiddotm
(c)
Option-4
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 69558kNmiddotm
(d)
Figure 15 Inelastic energy demands in structural components (a) to (d) For Option-1 to Option-4 respectively
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus20000 minus10000 0
Leve
l
Axial load (kN)
Option-1Option-2
Option-3Option-4
Figure 16 Axial load envelope in one typical column
Shock and Vibration 13
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus15000 0 15000 30000
Leve
l
minus5
0
5
10
15
20
25
30
35
40
Leve
l
Moment (kNmiddotm)
minus1200 minus800 minus400 0 400 800 1200
Shear (kN)
Option-1Option-2
Option-3Option-4
Option-1Option-2
Option-3Option-4
Figure 17 Moment and shear envelope in one typical column
minus20 minus10 00 10 20
Base
shea
r (kN
)
Top displacement (m)
Option-1Option-2
Option-3Option-4
300E + 04
200E + 04
100E + 04
000E + 00
minus100E + 04
minus200E + 04
minus300E + 04
Figure 18 Base shear versus top displacement relationship in firstmode load pattern
displacement is compared in Figure 18 It can be seen that thiscurve is flag shaped for Option-1 whereas it is bilinear pinch-ing type in Options-2ndash4There is no permanent deformationin controlled structure and flag shaped hysteresis behaviouris observed The same behaviour was observed during testconducted on a large-scale model of a concrete shear wallfrom the core of a high-rise building in the study of Adebar etal [27] The combination of low percentage of vertical rein-forcement and large axial compression force due to gravity
loads (axial force(concrete 28 days cylinder strength times grossarea ofwall)gt 01) caused the flexural cracks to closewhen thelateral load was removed In Options-2ndash4 small permanentdeformation (residual displacement) is observed This isbecause of the plastification of BRBs as well as transfer of themoment demand from shear wall to columns in the form ofaxial push-pull
8 Conclusions
(i) In this study different options of location of BRBsare investigated for a 40-story case study buildingThe locations of BRBs are identified based on theDBE elastic racking shear deformation and shear andbending moment demands in dominant 2nd and 3rdmodes NLRHA is then performed for seven sets ofspectrally matched target time histories and resultsare compared for different options
(ii) In all options shear force demands bending momentat mid height displacement demand racking sheardeformation demand and rotation demand in cou-pling beams are reduced by 10 45 45 45 and40 respectively in comparison to the controlledstructure
(iii) Rotational demand in the core wall at base level isreduced by 99 57 and 93 in Option-2 Option-3 and Option-4 respectively in comparison toOption-1Whereas energy dissipated by the core wallis reduced by around 250 in the corewall in compar-ison to the controlled structure Rotational demandand energy dissipation are measure of damage in thecore wall Thus damage can be significantly reducedby installation of BRBs
14 Shock and Vibration
(iv) All BRBs options are effective for bending momentreduction at mid height displacement and rackingshear deformation demands along the wall heightand rotation demand at the base of the wall and incoupling beams above the mid height of the build-ing However Option-4 in which BRBs are installedbetween peripheral columns and central corewall andcut in shear walls based on the maximum shear forceand bending moment leads to the highest reductionThis is because of the early yielding of the interiorbraces
(v) Thiswork is equally important for academia and prac-tising engineers especially those working in the fieldof performance based design of the high-rise build-ings in the commercial consultancy This will helpthem to locate BRBs at appropriate locations whiledesigning their buildings in an optimal way
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] International Conference of Building Officials Uniform Build-ing Code vol 2 International Conference of Building OfficialsWhittier Calif USA 1997
[2] J Maffei and N Yuen ldquoSeismic performance and designrequirements for high rise buildingsrdquo Structural Magazine pp28ndash32 2007
[3] J P Moehle ldquoPerformance-based seismic design of tall build-ings in the USrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[4] CEN EC8 Design of Structures for Earthquake ResistanceEuropean Committee for Standardization Brussels Belgium2004
[5] NZS 3101 Part 12006 Concrete Structures Standards NewZealand Standards New Zealand Wellington New Zealand2006
[6] T Paulay and M J N Priestley Seismic Design of ReinforcedConcrete and Masonry Buildings Wiley Hoboken NJ USA1992
[7] M Panagiotou J I Restrepo and J P Conte ldquoShake table test ofa 7-story full scale reinforced concrete structural wall buildingslice phase I rectangular wallrdquo Report SSRP 07-07 Departmentof Structural Engineering University of California San DiegoSan Diego Calif USA 2007
[8] Canadian Standard Association CSA Standard A233-04Design of Concrete Structures Canadian Standard AssociationRexdale Canada 2005
[9] R Klemencic J A Fry J D Hooper and B G MorgenldquoPerformance-based design of ductile concrete core wall build-ingsmdashissues to consider before detailed analysisrdquoTheStructuralDesign of Tall and Special Buildings vol 16 no 5 pp 599ndash6142007
[10] R Klemencic ldquoPerformance based seismic designmdashrisingrdquoStructural Magazine 2008 httpwwwstructuremagorgwp-contentuploads201408C-StructuralPractices-Klemencic-June081pdf
[11] A Zekioglu M Willford L Jin and M Melek ldquoCase studyusing the Los Angeles tall buildings structural design councilguidelines 40-storey concrete core wall buildingrdquo StructuralDesign of Tall and Special Buildings vol 16 no 5 pp 583ndash5972007
[12] B R Rad and P Adebar ldquoDynamic shear amplification inhigh-rise concrete walls effect of multiple flexural hinges andshear crackingrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[13] M Panagiotou and J I Restrepo ldquoDual-plastic hinge designconcept for reducing higher-mode effects on high-rise can-tilever wall buildingsrdquo Earthquake Engineering and StructuralDynamics vol 38 no 12 pp 1359ndash1380 2009
[14] M Ahmed and P Warnitchai ldquoReduction of inelastic seismicdemands by inducing plastic hinges at effective locationsrdquoin Proceedings of the 3rd Asian Conference on EarthquakeEngineering (ACEE rsquo10) Bangkok Thailand December 2010
[15] A Munir and P Warnitchai ldquoThe cause of unproportion-ately large higher mode contributions in the inelastic seismicresponses of high-rise core-wall buildingsrdquo Earthquake Engi-neering amp Structural Dynamics vol 41 no 15 pp 2195ndash22142012
[16] A Munir and P Warnitchai ldquoOptimal reduction of inelasticseismic demands in high-rise reinforced concrete core wallbuildings using energy-dissipating devicesrdquo Structural Design ofTall and Special Buildings vol 22 no 7 pp 543ndash568 2013
[17] M C Constantinou and M D Symans ldquoExperimental andanalytical investigation of seismic response of structures withsupplemental fluid viscous dampersrdquo NCEER Reports 92-0032State University of New York at Buffalo Buffalo NY USA 1992
[18] A SWhittaker V V Bertero C LThompson and L J AlonsoldquoSeismic testing of steel plate energy dissipation devicesrdquoEarthquake Spectra vol 7 no 4 pp 563ndash604 1991
[19] G W Housner L A Bergman T K Caughey et al ldquoStruc-tural control past present and futurerdquo Journal of EngineeringMechanics vol 123 no 9 pp 897ndash971 1997
[20] M D Symans F A Charney A S Whittaker et al ldquoEnergydissipation systems for seismic applications current practiceand recent developmentsrdquo Journal of Structural Engineering vol134 no 1 pp 3ndash21 2008
[21] C J Black N Makris and I D Aiken ldquoComponent testingseismic evaluation and characterization of buckling-restrainedbracesrdquo Journal of Structural Engineering vol 130 no 6 pp880ndash894 2004
[22] S Keten A performance based approach for seismic designwith hysteretic dampers [MS thesis] Massachusetts Institute ofTechnology (MIT) 2006 httpdspacemitedubitstreamhan-dle172113459571252112-MITpdfsequence=2
[23] N Anwar J A Sy T H Aung and D Rayamajhi ldquoFirstapplication of buckling restraint brace system in Philippines ina 50-story building with ductile core wall and PT slab systemrdquoin Proceedings of the 9th International Conference on UrbanEarthquake Engineering and the 4th Asia Conference on Earth-quake Engineering Tokyo Institute of Technology Tokyo JapanMarch 2012
[24] Computers and Structures Inc ETABS Extended 3D Analysis ofBuilding Systems Software Nonlinear Version 900 Computersand Structures Inc Berkeley Calif USA 2005
[25] Computers and Structures Perform 3D Nonlinear Analysis andPerformance Assessment for 3D Structures User Guide Version 4Computers and Structures Berkeley Calif USA 2006
Shock and Vibration 15
[26] J W Wallace and J P Moehle ldquoDuctility and detailing require-ments of bearing wall buildingsrdquo Journal of Structural Engineer-ing vol 118 no 6 pp 1625ndash1644 1992
[27] P Adebar A M M Ibrahim and M Bryson ldquoTest of high-risecore wall effective stiffness for seismic analysisrdquo ACI StructuralJournal vol 104 no 5 pp 549ndash559 2007
[28] FEMA ldquoPrestandard and commentary for the seismic rehabil-itation of buildingsrdquo FEMA 356 Federal Emergency Manage-ment Agency Washington DC USA 2000
[29] LATBDSC An Alternative Procedure for Seismic Analysis andDesign of Tall Buildings Located in Los Angeles Region A Con-sensus Document Los Angeles Tall Buildings and StructuralDesign Council 2008
[30] PEERNGAData Base Pacific Earthquake Engineering Research(PEER) University of California Berkeley Calif USA 2005httppeerberkeleyedunga
[31] COSMOS Data Base ldquoConsortium of organization for strong-motion observation systemsrdquo Tech Rep University of Cali-fornia Berkeley Calif USA 1999ndash2007 httpwwwcosmos-eqorgscriptsdefaultplx
[32] K Lilhanand and W S Tseng ldquoDevelopment and applicationof realistic earthquake time histories compatible with multipledamping design spectrardquo in Proceedings of the 9th World Con-ference on Earthquake Engineering Tokyo Japan August 1988
[33] J Hancock J Watson-Lamprey N A Abrahamson et al ldquoAnimproved method of matching response spectra of recordedearthquake ground motion using waveletsrdquo Journal of Earth-quake Engineering vol 10 no 1 pp 67ndash89 2006
[34] J B Mander M J N Priestley and R Park ldquoTheoreticalstress-strain model for confined concreterdquo Journal of StructuralEngineering New York vol 114 no 8 pp 1804ndash1826 1988
[35] CTBUH Seismic Working Group CTBUH Recommendationsfor the Seismic Design of High-Rise Buildings A ConsensusDocument 2008
[36] N Satake K-I Suda T Arakawa A Sasaki and Y TamuraldquoDamping evaluation using full-scale data of buildings inJapanrdquo Journal of Structural Engineering vol 129 no 4 pp 470ndash477 2003
[37] Q Xie ldquoState of the art of buckling-restrained braces in AsiardquoJournal of Constructional Steel Research vol 61 no 6 pp 727ndash748 2005
[38] P Clark K Kasai I Aiken E Ko and I Kimura ldquoDesign proce-dures for buildings incorporating hysteretic energy dissipatingdevicesrdquo in Proceedings of the 68th Annual Convention Struc-tural Engineers Association of California Santa Barbara CalifUSA October 1999
[39] D Vafaei and R Eskandari ldquoSeismic response of mega buck-ling-restrained braces subjected to fling-step and forward-directivity near-fault ground motionsrdquo Structural Design of Talland Special Buildings vol 24 no 9 pp 672ndash686 2015
[40] L Di Sarno and A S Elnashai ldquoBracing systems for seismicretrofitting of steel framesrdquo Journal of Constructional SteelResearch vol 65 no 2 pp 452ndash465 2009
[41] A Dutta and R O Hamburger ldquoCase study of A 40-Storeybuckling-restrained braced frame building located in LosAnge-lesrdquo The Structural Design of Tall and Special Buildings vol 19no 1-2 pp 77ndash93 2010
[42] Rutherford amp Chekene ldquoPerform nonlinear component mod-elling of star seismic powercat BRBsrdquo Report to Star SeismicLLC Star Seismic LLC 2011
[43] P Dusicka A M Itani and I G Buckle ldquoCyclic response ofplate steels under large inelastic strainsrdquo Journal of Construc-tional Steel Research vol 63 no 2 pp 156ndash164 2007
[44] S A Razavi M E Shemshadian S R Mirghaderi and SAhlehagh ldquoSeismic design of buckling restrained braced frameswith reduced core lengthrdquo in Proceedings of the The StructuralEngineers World Congress Cernobbio Italy 2011
[45] S A Razavi S R Mirghaderi A Hosseini and M EShemshadian ldquoReduced length buckling restrained brace usingsteel plates as restraining segmentrdquo in Proceedings of the 15thWorld Conference on Earthquake Engineering Lisboa PurtagalSeptember 2012
[46] M E Shemshadian S A Razavi S R Mirghaderi A Hosseiniand M K Mohammadi ldquoThe advantages of reducing thelength of yielding segment in seismic performance of bucklingrestrained braced framesrdquo inProceedings of the 6th InternationalConference of Seismology and Earthquake Engineering TehranIran 2011
[47] N Ma B Wu J Zhao H Li J Ou andW Yang ldquoFull scale testof all-steel buckling restrained bracesrdquo in Proceedings of the 14thWorld Conference on Earthquake Engineering Beijing ChinaOctober 2008
[48] L Di Sarno and G Manfredi ldquoSeismic retrofitting of existingRC frames with buckling restrained bracesrdquo in Proceedings ofthe Improving the Seismic Performance of Existing Buildingsand Other Structures pp 741ndash752 San Francisco Calif USADecember 2009
[49] S Ahlehagh Improvement of the special concentrically bracedsteel frames behaviour by employing balanced braces [MSthesis] University of Tehran Tehran Iran 2008
[50] R Tremblay P Bolduc R Neville and R DeVall ldquoSeismic test-ing and performance of buckling-restrained bracing systemsrdquoCanadian Journal of Civil Engineering vol 33 no 2 pp 183ndash1982006
Figure 5 Inelastic MCE shear and moment demands in the controlled structure
Encasing mortar
Yielding steel core
Steel tube
Unbonding materialbetween steel core
and mortar
Figure 6 Typical BRB
behaviour because its compression buckling is avoided due toencasing by an outer steel tubeThemain brace and outer tubeare separated by bonding material in order to accommodatethe lateral expansion due to its compression yielding [37] Atypical BRB is shown in Figure 6 [38]
52 Location of Buckling Restrained Braces BRBs have beeninstalled at several critical locations based on the results ofelastic modal decomposition analysis in dominant modessuch as 1st 2nd and 3rd modes and results are comparedwith controlled structure described in Section 4 (Option-1)In second option (Option-2) the BRBs have been installed
at bays 2 3 and 4 between peripheral columns and centralcore wall based on the maximum racking shear deformationdemands in 2nd and 3rd modes This arrangement is shownin Figure 7 In third option small size BRBs have also beeninstalled at bays 2 and 4 in cut in central core wall at the max-imum moment demands in 2nd and 3rd modes These BRBsare in addition to the BRBs in Option-2 This arrangementis shown in Figure 8 In final and fourth option (Option-4)BRBs have been installed in cut in central core wall at bays 2and 4 at the location of maximum shear force in 2nd and 3rdmodes in addition to the BRBs in Option-2 This is shownin Figure 9 It may be noted that the locations of BRBs in
Shock and Vibration 7
0
5
10
15
20
25
30
35
40
0
000
1
000
2
000
3
000
4
000
5
Leve
l
Racking shear deformation ratioMode-2Mode-3
Mode-4
Figure 7 Arrangement of the BRBs at locations of maximum racking shear deformation in exterior panels (Option-2)
0
5
10
15
20
25
30
35
40
0 1 2 3
Leve
l
0
5
10
15
20
25
30
35
40
Leve
l
Mode-2Mode-3
Mode-4 Mode-2Mode-3
Mode-4
Moment (kNmiddotm times 106)
0
000
1
000
2
000
3
000
4
000
5
Racking shear deformation ratio
Figure 8 Arrangement of the exterior BRBs at locations of maximum DBE elastic racking shear deformation in 2nd and 3rd mode andinterior BRBs at locations of maximum DBE elastic moment demands in 2nd and 3rd mode (Option-3)
8 Shock and Vibration
0
5
10
15
20
25
30
35
40Le
vel
0
5
10
15
20
25
30
35
40
0 50 100
Leve
l num
ber
Shear (kN times 103)
Mode-2Mode-3
Mode-4 Mode-2Mode-3
Mode-4
0
000
1
000
2
000
3
000
4
000
5
Racking shear deformation ratio
Figure 9 Arrangement of the exterior BRBs at locations of maximum DBE elastic racking shear deformation in 2nd and 3rd mode andinterior BRBs at locations of maximum DBE elastic shear demands in 2nd and 3rd mode (Option-3)
Option-1 Option-2 andOption-3 are also suitable for mode-1
The BRBs dissipate energy through axial tension andcompression To achieve maximum energy dissipation theBRBs should be placed at the proper locations and anglesEach BRB has been placed at an angle of approximately1205874 covering almost three stories for exterior brace and twostories for brace in cut in core wall These V-shaped BRBsconfigurations resemble the BRBs configuration used inmegabraced frames steel buildings reported in the previous studies[39ndash41] BRBs shall cross the slabs through purposely builtopenings provided in the slabs A horizontal drag elementis used from point where BRB connects to the column tothe central core wall to take care of the horizontal forcecomponent of the BRB axial force at column connection
53 Size of Buckling Restrained Braces Sizes of the BRBs havebeen selected by hit and trial using more rigorous nonlineartime history analyses (NLTHAs) using displacement-baseddesign approach Their size should neither be too large tobe uneconomical nor be too small to be ineffective The 119883-section of the braces between peripheral columns and centralcore wall is selected as 7500mm2 whereas it is 3750mm2for braces in cuts in core wall The buckling restrained bracesmanufactured by star seismic with normal yield strength of280MPa are used for braces between peripheral columnsand central core wall [42] However the low yield point-100(LYP100) steel core manufactured by Nippon Steel Corpora-tion Japan with specified yield strength of 100MPa is used
f
0DXDU
FY
FUO
FUH
KF
KO
Figure 10 Trilinear curve for BRBs
for braces in cut elements [22]The lowyield point steel bracesare used in cut in core wall to mainly achieve more energydissipation through the early yielding of the brace [43]
54 Modelling of Buckling Restrained Braces A BRB consistsof three components that is central yielding core brace endsmember connecting the central brace with the pin connec-tion and pin connection between brace and main structuralmembers The length of the exterior core brace is 45mwhereas length of the core brace in cut of core wall is 18mThese lengths are in the optimum range of 02ndash04 times thetotal length of the brace Several advantages such as simple
Shock and Vibration 9
minus4000
minus3000
minus2000
minus1000
0
1000
2000
3000
4000A
xial
forc
e ( k
N)
Axial def (m)
10E minus 0150E minus 0200E + 00minus50E minus 02
(a)
minus500
minus400
minus300
minus200
minus100
0
100
200
300
400
500
Axi
al fo
rce (
kN
)
Axial def (m)
20E
minus03
10E
minus03
00E
+00
minus30E
minus03
minus20E
minus03
minus10E
minus03
(b)
Figure 11 Typical cyclic response of BRBs obtained from the analysis (a) Exterior brace (b) interior brace
replacement lesser weight concrete elimination economyand easy erection process are associated with reduced lengthof the core brace [44ndash50] BRB has been modelled using theBRB compound component of the Perform-3D Such mem-ber is composed of three components that is (1) a BRB basiccomponent for main yielding brace (2) an elastic bar basiccomponent for member connecting brace with gusset plateand (3) a stiff end zone which accounts for the gusset platesand so forth at both ends of the member
The positive side (tension) of the trilinear curve to definethe force-deformation of the BRBs is shown in Figure 10 Itcan be seen that after yielding there are two lines such asbottom and top line The bottom line is used to simulate firstcyclic load and the top line is used to simulate full strainhardening The same behavior has been observed in testslike the hysteresis loop which can progressively grow in sizeThis is sometimes referred to as ldquoisotropic hardeningrdquo Thisleads to the component increase in strength under cyclic loadThe negative side of the curve shows a little variation due todifference in the values of compression and tensions FY FUO(FUO (T) = 105 FY FUO (C) = 104 FY) and FUH (FUO(T) = 134 FY FUO (C) = 151 FY) are yield strength strengthat first loading cycle and strength of the core brace afterfull hardening respectively DU (DU (T) = 07 DU (C) =07) is the deformation at FUO and DX (DX (T) = 004 LYCDX (C) = 004 LYC) is the maximum deformation of thebrace LYC is the length of the yielding core KO is theInitial stiffness of the core brace and KF (= 002KO) is theslope of third line [42] The strain hardening properties suchas deformation at FUO-FUH average are taken equal to 2times (LYC180) and deformation at FUH is taken as 35times (LYC180) The typical force-deformation relationshipfor exterior (between peripheral columns and core wall) andinterior BRB (in cut in core wall) obtained from NLRHAanalysis for a particular ground motion is shown in Figures11(a) and 11(b) respectivelyThese figures show that hysteresisloop is similar to the reported Clark et al 1999 [38] provingthat performing BRB element can capture the behaviour
appropriately The size of the elastic bar element is selectedsuch that it can safely carry maximum axial force in brace inelastic range to conform to the capacity design approach Stiffend zone is few times stiffer than the elastic bar element
6 Comparison of the Responses in DifferentOptions and Discussion on the Results
NLRHA is performed using seven spectrally matched timehistories Different response quantities such as displacementplastic hinge rotations in coupling beams and core wall sheardeformation angle (story racking shear deformation) bend-ing moment shear force and energy demands are obtainedfrom this analysisThe plastic rotations are calculated bymul-tiplying the average curvature of the wall at mid height withthe plastic hinge length The mean value of different quan-tities obtained from seven ground motions are shown anddiscussed in following paragraphs
Shear demands obtained from four options are shownin Figure 12(a) Shear demand pattern and magnitude aresimilar in all options Moment demands obtained from fouroptions are shown in Figure 12(b) The moment demand atthe base is similar in all four options because this is clippedto the flexural strength of the plastic hinge at the base of thewall However it is reduced along the wall height by 30 35and 40 in Option-2 Option-3 and Option-4 respectivelyin comparison to that in 1st optionThe reduction inmomentdemand is significant in all options This will help to avoidreinforcement congestion in the wall near mid height
Displacement demands obtained from four options areshown in Figure 13(a) Displacement demand pattern is simi-lar for all options However displacement demand is reducedalong thewall height by 40 40 and 60 inOption-2 Option-3 and Option-4 respectively in comparison to that in 1stoption Racking shear deformation demands obtained fromfour options are shown in Figure 13(b) The racking sheardeformation demand patterns are similar for all four optionsHowever racking shear deformation demands are reduced
10 Shock and Vibration
minus5
0
5
10
15
20
25
30
35
40
0 50000 100000 150000
Leve
l
Shear force (kN)
Option-1Option-2
Option-3Option-4
(a)
minus5
0
5
10
15
20
25
30
35
40
Leve
l
0 1 2 3
Option-1Option-2
Option-3Option-4
Bending moment (kNmiddotm times 106)
(b)
Figure 12 MCE inelastic shear and moment demands in different options (a) Shear (b) moment
0 05 1 15 2 25Displacement (m)minus5
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(a)
0 001 002 003 004Racking shear deformation ratio
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(b)
Figure 13 MCE inelastic displacement and racking deformation demands in different options (a) Displacement (b) racking sheardeformation angle
along the wall height by 40 40 and 65 in Option-2Option-3 and Option-4 respectively in comparison to thatin 1st option This is significant reduction Racking sheardeformations of 0036 in the controlled structures are reducedto 0023 which is well within the limit of 003 set by [29]LATBSDC 2008 for the MCE level earthquake
Rotational demands in the core wall at the base level aswell as in coupling beams along the height are shown in Fig-ures 14(a) and 14(b) respectivelyThe rotation demand in thewall is calculated by multiplying the average curvature at themid height of the inelastic wall element by height of the wallThe comparison shows that themaximum rotational demand
at the base of the wall is reduced by 99 57 and 93 inOption-2Option-3 andOption-4 respectively in comparison to thatin 1st option This is strong indication that damage at thebase of the wall shall be reduced to half and consequentlyextent of repair shall be small and hence cheap in case ofsevere MCE events such as DBE and MCE level earthquakeThe rotational demands in coupling beams are reduced by52 40 and 35 respectively above the half height level forOption-2 Option-3 and Option-4 respectively in compar-ison to 1st option However rotation demand remained thesame in the lower half portion of the building for all options
Energy dissipated by core wall coupling beams andbuckling restrained braces have been compared in Figures15(a)ndash15(d) respectively for Option-1 Option-2 Option-3 and Option-4 respectively This is energy dissipated inpercentage of the total energy demand in the structure Thetotal energy demand is sum of the kinetic energy elasticstrain energy energy dissipated by elastic modal dampingand energy dissipation by damage in structural elements suchas core wall coupling beams and BRBs About 83 9292 and 90 energy have been dissipated by elastic modaland inelastic damping in Option-1 to Option-4 respectivelyThe energy dissipation by modal elastic damping to the totalenergy demands is 50 37 35 and 33 respectively inOption-1 to Option-4 respectivelyThe energy dissipation bycore wall at the base to the total energy demands is 22 66 and 6 inOption-1 to Option-4 respectivelyThe energydissipation by coupling beams to the total energy demands isapproximately 10 4 5 and 6 in Option-1 to Option-4 respectively The energy dissipation by BRBs to the total
energy demands is 0 45 45 and 45 respectively inOption-1 to Option-4
7 Effects of BRBs on Axial Loads Shearand Moment of Columns and PermanentDeformation due to BRBs Plastification
Effects of BRBs on axial loads of columns and permanentdeformation due to BRBs plastification have been discussedin this section The axial load envelope in a typical columnfor Options-1ndash4 is shown in the Figure 16 The magnitude ofaxial load is same for Options-2ndash4 (with BRBs) and is twicethan that in Option-1 (controlled structure) This is due tothe outrigger effect created by the connection of columnsand core wall through BRBs Some core wall moment hasbeen resisted by the development of axial push-pull in thecolumns Furthermore the shape of the axial load envelopeis smooth in case of Option-1 whereas it is jagged at thelocations of the BRBs forOptions-2ndash4Themoment envelopeand shear envelope for one typical column are shown inFigures 17(a) and 17(b) respectively It shows that momentand shear have been reduced at the ground level in Options-2ndash4 in comparison to Option-1 whereas these remain almostthe same at upper portions The extra moment and shearat the ground level in Options-1ndash4 is due to the transfer ofmoment and shear to the columns when core wall yields
To better understand the permanent deformation in thestructure due to BRBs plastification cyclic pushover analysisin firstmode is performedusing target displacement obtainedfrom NLTHA for all cases The cyclic base shear versus top
12 Shock and Vibration
Option-1
0
20
40
60
80
100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 53478kNmiddotm
(a)
Option-2
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 73328kNmiddotm
(b)
Option-3
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80 90
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 71449kNmiddotm
(c)
Option-4
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 69558kNmiddotm
(d)
Figure 15 Inelastic energy demands in structural components (a) to (d) For Option-1 to Option-4 respectively
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus20000 minus10000 0
Leve
l
Axial load (kN)
Option-1Option-2
Option-3Option-4
Figure 16 Axial load envelope in one typical column
Shock and Vibration 13
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus15000 0 15000 30000
Leve
l
minus5
0
5
10
15
20
25
30
35
40
Leve
l
Moment (kNmiddotm)
minus1200 minus800 minus400 0 400 800 1200
Shear (kN)
Option-1Option-2
Option-3Option-4
Option-1Option-2
Option-3Option-4
Figure 17 Moment and shear envelope in one typical column
minus20 minus10 00 10 20
Base
shea
r (kN
)
Top displacement (m)
Option-1Option-2
Option-3Option-4
300E + 04
200E + 04
100E + 04
000E + 00
minus100E + 04
minus200E + 04
minus300E + 04
Figure 18 Base shear versus top displacement relationship in firstmode load pattern
displacement is compared in Figure 18 It can be seen that thiscurve is flag shaped for Option-1 whereas it is bilinear pinch-ing type in Options-2ndash4There is no permanent deformationin controlled structure and flag shaped hysteresis behaviouris observed The same behaviour was observed during testconducted on a large-scale model of a concrete shear wallfrom the core of a high-rise building in the study of Adebar etal [27] The combination of low percentage of vertical rein-forcement and large axial compression force due to gravity
loads (axial force(concrete 28 days cylinder strength times grossarea ofwall)gt 01) caused the flexural cracks to closewhen thelateral load was removed In Options-2ndash4 small permanentdeformation (residual displacement) is observed This isbecause of the plastification of BRBs as well as transfer of themoment demand from shear wall to columns in the form ofaxial push-pull
8 Conclusions
(i) In this study different options of location of BRBsare investigated for a 40-story case study buildingThe locations of BRBs are identified based on theDBE elastic racking shear deformation and shear andbending moment demands in dominant 2nd and 3rdmodes NLRHA is then performed for seven sets ofspectrally matched target time histories and resultsare compared for different options
(ii) In all options shear force demands bending momentat mid height displacement demand racking sheardeformation demand and rotation demand in cou-pling beams are reduced by 10 45 45 45 and40 respectively in comparison to the controlledstructure
(iii) Rotational demand in the core wall at base level isreduced by 99 57 and 93 in Option-2 Option-3 and Option-4 respectively in comparison toOption-1Whereas energy dissipated by the core wallis reduced by around 250 in the corewall in compar-ison to the controlled structure Rotational demandand energy dissipation are measure of damage in thecore wall Thus damage can be significantly reducedby installation of BRBs
14 Shock and Vibration
(iv) All BRBs options are effective for bending momentreduction at mid height displacement and rackingshear deformation demands along the wall heightand rotation demand at the base of the wall and incoupling beams above the mid height of the build-ing However Option-4 in which BRBs are installedbetween peripheral columns and central corewall andcut in shear walls based on the maximum shear forceand bending moment leads to the highest reductionThis is because of the early yielding of the interiorbraces
(v) Thiswork is equally important for academia and prac-tising engineers especially those working in the fieldof performance based design of the high-rise build-ings in the commercial consultancy This will helpthem to locate BRBs at appropriate locations whiledesigning their buildings in an optimal way
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] International Conference of Building Officials Uniform Build-ing Code vol 2 International Conference of Building OfficialsWhittier Calif USA 1997
[2] J Maffei and N Yuen ldquoSeismic performance and designrequirements for high rise buildingsrdquo Structural Magazine pp28ndash32 2007
[3] J P Moehle ldquoPerformance-based seismic design of tall build-ings in the USrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[4] CEN EC8 Design of Structures for Earthquake ResistanceEuropean Committee for Standardization Brussels Belgium2004
[5] NZS 3101 Part 12006 Concrete Structures Standards NewZealand Standards New Zealand Wellington New Zealand2006
[6] T Paulay and M J N Priestley Seismic Design of ReinforcedConcrete and Masonry Buildings Wiley Hoboken NJ USA1992
[7] M Panagiotou J I Restrepo and J P Conte ldquoShake table test ofa 7-story full scale reinforced concrete structural wall buildingslice phase I rectangular wallrdquo Report SSRP 07-07 Departmentof Structural Engineering University of California San DiegoSan Diego Calif USA 2007
[8] Canadian Standard Association CSA Standard A233-04Design of Concrete Structures Canadian Standard AssociationRexdale Canada 2005
[9] R Klemencic J A Fry J D Hooper and B G MorgenldquoPerformance-based design of ductile concrete core wall build-ingsmdashissues to consider before detailed analysisrdquoTheStructuralDesign of Tall and Special Buildings vol 16 no 5 pp 599ndash6142007
[10] R Klemencic ldquoPerformance based seismic designmdashrisingrdquoStructural Magazine 2008 httpwwwstructuremagorgwp-contentuploads201408C-StructuralPractices-Klemencic-June081pdf
[11] A Zekioglu M Willford L Jin and M Melek ldquoCase studyusing the Los Angeles tall buildings structural design councilguidelines 40-storey concrete core wall buildingrdquo StructuralDesign of Tall and Special Buildings vol 16 no 5 pp 583ndash5972007
[12] B R Rad and P Adebar ldquoDynamic shear amplification inhigh-rise concrete walls effect of multiple flexural hinges andshear crackingrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[13] M Panagiotou and J I Restrepo ldquoDual-plastic hinge designconcept for reducing higher-mode effects on high-rise can-tilever wall buildingsrdquo Earthquake Engineering and StructuralDynamics vol 38 no 12 pp 1359ndash1380 2009
[14] M Ahmed and P Warnitchai ldquoReduction of inelastic seismicdemands by inducing plastic hinges at effective locationsrdquoin Proceedings of the 3rd Asian Conference on EarthquakeEngineering (ACEE rsquo10) Bangkok Thailand December 2010
[15] A Munir and P Warnitchai ldquoThe cause of unproportion-ately large higher mode contributions in the inelastic seismicresponses of high-rise core-wall buildingsrdquo Earthquake Engi-neering amp Structural Dynamics vol 41 no 15 pp 2195ndash22142012
[16] A Munir and P Warnitchai ldquoOptimal reduction of inelasticseismic demands in high-rise reinforced concrete core wallbuildings using energy-dissipating devicesrdquo Structural Design ofTall and Special Buildings vol 22 no 7 pp 543ndash568 2013
[17] M C Constantinou and M D Symans ldquoExperimental andanalytical investigation of seismic response of structures withsupplemental fluid viscous dampersrdquo NCEER Reports 92-0032State University of New York at Buffalo Buffalo NY USA 1992
[18] A SWhittaker V V Bertero C LThompson and L J AlonsoldquoSeismic testing of steel plate energy dissipation devicesrdquoEarthquake Spectra vol 7 no 4 pp 563ndash604 1991
[19] G W Housner L A Bergman T K Caughey et al ldquoStruc-tural control past present and futurerdquo Journal of EngineeringMechanics vol 123 no 9 pp 897ndash971 1997
[20] M D Symans F A Charney A S Whittaker et al ldquoEnergydissipation systems for seismic applications current practiceand recent developmentsrdquo Journal of Structural Engineering vol134 no 1 pp 3ndash21 2008
[21] C J Black N Makris and I D Aiken ldquoComponent testingseismic evaluation and characterization of buckling-restrainedbracesrdquo Journal of Structural Engineering vol 130 no 6 pp880ndash894 2004
[22] S Keten A performance based approach for seismic designwith hysteretic dampers [MS thesis] Massachusetts Institute ofTechnology (MIT) 2006 httpdspacemitedubitstreamhan-dle172113459571252112-MITpdfsequence=2
[23] N Anwar J A Sy T H Aung and D Rayamajhi ldquoFirstapplication of buckling restraint brace system in Philippines ina 50-story building with ductile core wall and PT slab systemrdquoin Proceedings of the 9th International Conference on UrbanEarthquake Engineering and the 4th Asia Conference on Earth-quake Engineering Tokyo Institute of Technology Tokyo JapanMarch 2012
[24] Computers and Structures Inc ETABS Extended 3D Analysis ofBuilding Systems Software Nonlinear Version 900 Computersand Structures Inc Berkeley Calif USA 2005
[25] Computers and Structures Perform 3D Nonlinear Analysis andPerformance Assessment for 3D Structures User Guide Version 4Computers and Structures Berkeley Calif USA 2006
Shock and Vibration 15
[26] J W Wallace and J P Moehle ldquoDuctility and detailing require-ments of bearing wall buildingsrdquo Journal of Structural Engineer-ing vol 118 no 6 pp 1625ndash1644 1992
[27] P Adebar A M M Ibrahim and M Bryson ldquoTest of high-risecore wall effective stiffness for seismic analysisrdquo ACI StructuralJournal vol 104 no 5 pp 549ndash559 2007
[28] FEMA ldquoPrestandard and commentary for the seismic rehabil-itation of buildingsrdquo FEMA 356 Federal Emergency Manage-ment Agency Washington DC USA 2000
[29] LATBDSC An Alternative Procedure for Seismic Analysis andDesign of Tall Buildings Located in Los Angeles Region A Con-sensus Document Los Angeles Tall Buildings and StructuralDesign Council 2008
[30] PEERNGAData Base Pacific Earthquake Engineering Research(PEER) University of California Berkeley Calif USA 2005httppeerberkeleyedunga
[31] COSMOS Data Base ldquoConsortium of organization for strong-motion observation systemsrdquo Tech Rep University of Cali-fornia Berkeley Calif USA 1999ndash2007 httpwwwcosmos-eqorgscriptsdefaultplx
[32] K Lilhanand and W S Tseng ldquoDevelopment and applicationof realistic earthquake time histories compatible with multipledamping design spectrardquo in Proceedings of the 9th World Con-ference on Earthquake Engineering Tokyo Japan August 1988
[33] J Hancock J Watson-Lamprey N A Abrahamson et al ldquoAnimproved method of matching response spectra of recordedearthquake ground motion using waveletsrdquo Journal of Earth-quake Engineering vol 10 no 1 pp 67ndash89 2006
[34] J B Mander M J N Priestley and R Park ldquoTheoreticalstress-strain model for confined concreterdquo Journal of StructuralEngineering New York vol 114 no 8 pp 1804ndash1826 1988
[35] CTBUH Seismic Working Group CTBUH Recommendationsfor the Seismic Design of High-Rise Buildings A ConsensusDocument 2008
[36] N Satake K-I Suda T Arakawa A Sasaki and Y TamuraldquoDamping evaluation using full-scale data of buildings inJapanrdquo Journal of Structural Engineering vol 129 no 4 pp 470ndash477 2003
[37] Q Xie ldquoState of the art of buckling-restrained braces in AsiardquoJournal of Constructional Steel Research vol 61 no 6 pp 727ndash748 2005
[38] P Clark K Kasai I Aiken E Ko and I Kimura ldquoDesign proce-dures for buildings incorporating hysteretic energy dissipatingdevicesrdquo in Proceedings of the 68th Annual Convention Struc-tural Engineers Association of California Santa Barbara CalifUSA October 1999
[39] D Vafaei and R Eskandari ldquoSeismic response of mega buck-ling-restrained braces subjected to fling-step and forward-directivity near-fault ground motionsrdquo Structural Design of Talland Special Buildings vol 24 no 9 pp 672ndash686 2015
[40] L Di Sarno and A S Elnashai ldquoBracing systems for seismicretrofitting of steel framesrdquo Journal of Constructional SteelResearch vol 65 no 2 pp 452ndash465 2009
[41] A Dutta and R O Hamburger ldquoCase study of A 40-Storeybuckling-restrained braced frame building located in LosAnge-lesrdquo The Structural Design of Tall and Special Buildings vol 19no 1-2 pp 77ndash93 2010
[42] Rutherford amp Chekene ldquoPerform nonlinear component mod-elling of star seismic powercat BRBsrdquo Report to Star SeismicLLC Star Seismic LLC 2011
[43] P Dusicka A M Itani and I G Buckle ldquoCyclic response ofplate steels under large inelastic strainsrdquo Journal of Construc-tional Steel Research vol 63 no 2 pp 156ndash164 2007
[44] S A Razavi M E Shemshadian S R Mirghaderi and SAhlehagh ldquoSeismic design of buckling restrained braced frameswith reduced core lengthrdquo in Proceedings of the The StructuralEngineers World Congress Cernobbio Italy 2011
[45] S A Razavi S R Mirghaderi A Hosseini and M EShemshadian ldquoReduced length buckling restrained brace usingsteel plates as restraining segmentrdquo in Proceedings of the 15thWorld Conference on Earthquake Engineering Lisboa PurtagalSeptember 2012
[46] M E Shemshadian S A Razavi S R Mirghaderi A Hosseiniand M K Mohammadi ldquoThe advantages of reducing thelength of yielding segment in seismic performance of bucklingrestrained braced framesrdquo inProceedings of the 6th InternationalConference of Seismology and Earthquake Engineering TehranIran 2011
[47] N Ma B Wu J Zhao H Li J Ou andW Yang ldquoFull scale testof all-steel buckling restrained bracesrdquo in Proceedings of the 14thWorld Conference on Earthquake Engineering Beijing ChinaOctober 2008
[48] L Di Sarno and G Manfredi ldquoSeismic retrofitting of existingRC frames with buckling restrained bracesrdquo in Proceedings ofthe Improving the Seismic Performance of Existing Buildingsand Other Structures pp 741ndash752 San Francisco Calif USADecember 2009
[49] S Ahlehagh Improvement of the special concentrically bracedsteel frames behaviour by employing balanced braces [MSthesis] University of Tehran Tehran Iran 2008
[50] R Tremblay P Bolduc R Neville and R DeVall ldquoSeismic test-ing and performance of buckling-restrained bracing systemsrdquoCanadian Journal of Civil Engineering vol 33 no 2 pp 183ndash1982006
Figure 7 Arrangement of the BRBs at locations of maximum racking shear deformation in exterior panels (Option-2)
0
5
10
15
20
25
30
35
40
0 1 2 3
Leve
l
0
5
10
15
20
25
30
35
40
Leve
l
Mode-2Mode-3
Mode-4 Mode-2Mode-3
Mode-4
Moment (kNmiddotm times 106)
0
000
1
000
2
000
3
000
4
000
5
Racking shear deformation ratio
Figure 8 Arrangement of the exterior BRBs at locations of maximum DBE elastic racking shear deformation in 2nd and 3rd mode andinterior BRBs at locations of maximum DBE elastic moment demands in 2nd and 3rd mode (Option-3)
8 Shock and Vibration
0
5
10
15
20
25
30
35
40Le
vel
0
5
10
15
20
25
30
35
40
0 50 100
Leve
l num
ber
Shear (kN times 103)
Mode-2Mode-3
Mode-4 Mode-2Mode-3
Mode-4
0
000
1
000
2
000
3
000
4
000
5
Racking shear deformation ratio
Figure 9 Arrangement of the exterior BRBs at locations of maximum DBE elastic racking shear deformation in 2nd and 3rd mode andinterior BRBs at locations of maximum DBE elastic shear demands in 2nd and 3rd mode (Option-3)
Option-1 Option-2 andOption-3 are also suitable for mode-1
The BRBs dissipate energy through axial tension andcompression To achieve maximum energy dissipation theBRBs should be placed at the proper locations and anglesEach BRB has been placed at an angle of approximately1205874 covering almost three stories for exterior brace and twostories for brace in cut in core wall These V-shaped BRBsconfigurations resemble the BRBs configuration used inmegabraced frames steel buildings reported in the previous studies[39ndash41] BRBs shall cross the slabs through purposely builtopenings provided in the slabs A horizontal drag elementis used from point where BRB connects to the column tothe central core wall to take care of the horizontal forcecomponent of the BRB axial force at column connection
53 Size of Buckling Restrained Braces Sizes of the BRBs havebeen selected by hit and trial using more rigorous nonlineartime history analyses (NLTHAs) using displacement-baseddesign approach Their size should neither be too large tobe uneconomical nor be too small to be ineffective The 119883-section of the braces between peripheral columns and centralcore wall is selected as 7500mm2 whereas it is 3750mm2for braces in cuts in core wall The buckling restrained bracesmanufactured by star seismic with normal yield strength of280MPa are used for braces between peripheral columnsand central core wall [42] However the low yield point-100(LYP100) steel core manufactured by Nippon Steel Corpora-tion Japan with specified yield strength of 100MPa is used
f
0DXDU
FY
FUO
FUH
KF
KO
Figure 10 Trilinear curve for BRBs
for braces in cut elements [22]The lowyield point steel bracesare used in cut in core wall to mainly achieve more energydissipation through the early yielding of the brace [43]
54 Modelling of Buckling Restrained Braces A BRB consistsof three components that is central yielding core brace endsmember connecting the central brace with the pin connec-tion and pin connection between brace and main structuralmembers The length of the exterior core brace is 45mwhereas length of the core brace in cut of core wall is 18mThese lengths are in the optimum range of 02ndash04 times thetotal length of the brace Several advantages such as simple
Shock and Vibration 9
minus4000
minus3000
minus2000
minus1000
0
1000
2000
3000
4000A
xial
forc
e ( k
N)
Axial def (m)
10E minus 0150E minus 0200E + 00minus50E minus 02
(a)
minus500
minus400
minus300
minus200
minus100
0
100
200
300
400
500
Axi
al fo
rce (
kN
)
Axial def (m)
20E
minus03
10E
minus03
00E
+00
minus30E
minus03
minus20E
minus03
minus10E
minus03
(b)
Figure 11 Typical cyclic response of BRBs obtained from the analysis (a) Exterior brace (b) interior brace
replacement lesser weight concrete elimination economyand easy erection process are associated with reduced lengthof the core brace [44ndash50] BRB has been modelled using theBRB compound component of the Perform-3D Such mem-ber is composed of three components that is (1) a BRB basiccomponent for main yielding brace (2) an elastic bar basiccomponent for member connecting brace with gusset plateand (3) a stiff end zone which accounts for the gusset platesand so forth at both ends of the member
The positive side (tension) of the trilinear curve to definethe force-deformation of the BRBs is shown in Figure 10 Itcan be seen that after yielding there are two lines such asbottom and top line The bottom line is used to simulate firstcyclic load and the top line is used to simulate full strainhardening The same behavior has been observed in testslike the hysteresis loop which can progressively grow in sizeThis is sometimes referred to as ldquoisotropic hardeningrdquo Thisleads to the component increase in strength under cyclic loadThe negative side of the curve shows a little variation due todifference in the values of compression and tensions FY FUO(FUO (T) = 105 FY FUO (C) = 104 FY) and FUH (FUO(T) = 134 FY FUO (C) = 151 FY) are yield strength strengthat first loading cycle and strength of the core brace afterfull hardening respectively DU (DU (T) = 07 DU (C) =07) is the deformation at FUO and DX (DX (T) = 004 LYCDX (C) = 004 LYC) is the maximum deformation of thebrace LYC is the length of the yielding core KO is theInitial stiffness of the core brace and KF (= 002KO) is theslope of third line [42] The strain hardening properties suchas deformation at FUO-FUH average are taken equal to 2times (LYC180) and deformation at FUH is taken as 35times (LYC180) The typical force-deformation relationshipfor exterior (between peripheral columns and core wall) andinterior BRB (in cut in core wall) obtained from NLRHAanalysis for a particular ground motion is shown in Figures11(a) and 11(b) respectivelyThese figures show that hysteresisloop is similar to the reported Clark et al 1999 [38] provingthat performing BRB element can capture the behaviour
appropriately The size of the elastic bar element is selectedsuch that it can safely carry maximum axial force in brace inelastic range to conform to the capacity design approach Stiffend zone is few times stiffer than the elastic bar element
6 Comparison of the Responses in DifferentOptions and Discussion on the Results
NLRHA is performed using seven spectrally matched timehistories Different response quantities such as displacementplastic hinge rotations in coupling beams and core wall sheardeformation angle (story racking shear deformation) bend-ing moment shear force and energy demands are obtainedfrom this analysisThe plastic rotations are calculated bymul-tiplying the average curvature of the wall at mid height withthe plastic hinge length The mean value of different quan-tities obtained from seven ground motions are shown anddiscussed in following paragraphs
Shear demands obtained from four options are shownin Figure 12(a) Shear demand pattern and magnitude aresimilar in all options Moment demands obtained from fouroptions are shown in Figure 12(b) The moment demand atthe base is similar in all four options because this is clippedto the flexural strength of the plastic hinge at the base of thewall However it is reduced along the wall height by 30 35and 40 in Option-2 Option-3 and Option-4 respectivelyin comparison to that in 1st optionThe reduction inmomentdemand is significant in all options This will help to avoidreinforcement congestion in the wall near mid height
Displacement demands obtained from four options areshown in Figure 13(a) Displacement demand pattern is simi-lar for all options However displacement demand is reducedalong thewall height by 40 40 and 60 inOption-2 Option-3 and Option-4 respectively in comparison to that in 1stoption Racking shear deformation demands obtained fromfour options are shown in Figure 13(b) The racking sheardeformation demand patterns are similar for all four optionsHowever racking shear deformation demands are reduced
10 Shock and Vibration
minus5
0
5
10
15
20
25
30
35
40
0 50000 100000 150000
Leve
l
Shear force (kN)
Option-1Option-2
Option-3Option-4
(a)
minus5
0
5
10
15
20
25
30
35
40
Leve
l
0 1 2 3
Option-1Option-2
Option-3Option-4
Bending moment (kNmiddotm times 106)
(b)
Figure 12 MCE inelastic shear and moment demands in different options (a) Shear (b) moment
0 05 1 15 2 25Displacement (m)minus5
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(a)
0 001 002 003 004Racking shear deformation ratio
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(b)
Figure 13 MCE inelastic displacement and racking deformation demands in different options (a) Displacement (b) racking sheardeformation angle
along the wall height by 40 40 and 65 in Option-2Option-3 and Option-4 respectively in comparison to thatin 1st option This is significant reduction Racking sheardeformations of 0036 in the controlled structures are reducedto 0023 which is well within the limit of 003 set by [29]LATBSDC 2008 for the MCE level earthquake
Rotational demands in the core wall at the base level aswell as in coupling beams along the height are shown in Fig-ures 14(a) and 14(b) respectivelyThe rotation demand in thewall is calculated by multiplying the average curvature at themid height of the inelastic wall element by height of the wallThe comparison shows that themaximum rotational demand
at the base of the wall is reduced by 99 57 and 93 inOption-2Option-3 andOption-4 respectively in comparison to thatin 1st option This is strong indication that damage at thebase of the wall shall be reduced to half and consequentlyextent of repair shall be small and hence cheap in case ofsevere MCE events such as DBE and MCE level earthquakeThe rotational demands in coupling beams are reduced by52 40 and 35 respectively above the half height level forOption-2 Option-3 and Option-4 respectively in compar-ison to 1st option However rotation demand remained thesame in the lower half portion of the building for all options
Energy dissipated by core wall coupling beams andbuckling restrained braces have been compared in Figures15(a)ndash15(d) respectively for Option-1 Option-2 Option-3 and Option-4 respectively This is energy dissipated inpercentage of the total energy demand in the structure Thetotal energy demand is sum of the kinetic energy elasticstrain energy energy dissipated by elastic modal dampingand energy dissipation by damage in structural elements suchas core wall coupling beams and BRBs About 83 9292 and 90 energy have been dissipated by elastic modaland inelastic damping in Option-1 to Option-4 respectivelyThe energy dissipation by modal elastic damping to the totalenergy demands is 50 37 35 and 33 respectively inOption-1 to Option-4 respectivelyThe energy dissipation bycore wall at the base to the total energy demands is 22 66 and 6 inOption-1 to Option-4 respectivelyThe energydissipation by coupling beams to the total energy demands isapproximately 10 4 5 and 6 in Option-1 to Option-4 respectively The energy dissipation by BRBs to the total
energy demands is 0 45 45 and 45 respectively inOption-1 to Option-4
7 Effects of BRBs on Axial Loads Shearand Moment of Columns and PermanentDeformation due to BRBs Plastification
Effects of BRBs on axial loads of columns and permanentdeformation due to BRBs plastification have been discussedin this section The axial load envelope in a typical columnfor Options-1ndash4 is shown in the Figure 16 The magnitude ofaxial load is same for Options-2ndash4 (with BRBs) and is twicethan that in Option-1 (controlled structure) This is due tothe outrigger effect created by the connection of columnsand core wall through BRBs Some core wall moment hasbeen resisted by the development of axial push-pull in thecolumns Furthermore the shape of the axial load envelopeis smooth in case of Option-1 whereas it is jagged at thelocations of the BRBs forOptions-2ndash4Themoment envelopeand shear envelope for one typical column are shown inFigures 17(a) and 17(b) respectively It shows that momentand shear have been reduced at the ground level in Options-2ndash4 in comparison to Option-1 whereas these remain almostthe same at upper portions The extra moment and shearat the ground level in Options-1ndash4 is due to the transfer ofmoment and shear to the columns when core wall yields
To better understand the permanent deformation in thestructure due to BRBs plastification cyclic pushover analysisin firstmode is performedusing target displacement obtainedfrom NLTHA for all cases The cyclic base shear versus top
12 Shock and Vibration
Option-1
0
20
40
60
80
100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 53478kNmiddotm
(a)
Option-2
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 73328kNmiddotm
(b)
Option-3
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80 90
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 71449kNmiddotm
(c)
Option-4
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 69558kNmiddotm
(d)
Figure 15 Inelastic energy demands in structural components (a) to (d) For Option-1 to Option-4 respectively
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus20000 minus10000 0
Leve
l
Axial load (kN)
Option-1Option-2
Option-3Option-4
Figure 16 Axial load envelope in one typical column
Shock and Vibration 13
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus15000 0 15000 30000
Leve
l
minus5
0
5
10
15
20
25
30
35
40
Leve
l
Moment (kNmiddotm)
minus1200 minus800 minus400 0 400 800 1200
Shear (kN)
Option-1Option-2
Option-3Option-4
Option-1Option-2
Option-3Option-4
Figure 17 Moment and shear envelope in one typical column
minus20 minus10 00 10 20
Base
shea
r (kN
)
Top displacement (m)
Option-1Option-2
Option-3Option-4
300E + 04
200E + 04
100E + 04
000E + 00
minus100E + 04
minus200E + 04
minus300E + 04
Figure 18 Base shear versus top displacement relationship in firstmode load pattern
displacement is compared in Figure 18 It can be seen that thiscurve is flag shaped for Option-1 whereas it is bilinear pinch-ing type in Options-2ndash4There is no permanent deformationin controlled structure and flag shaped hysteresis behaviouris observed The same behaviour was observed during testconducted on a large-scale model of a concrete shear wallfrom the core of a high-rise building in the study of Adebar etal [27] The combination of low percentage of vertical rein-forcement and large axial compression force due to gravity
loads (axial force(concrete 28 days cylinder strength times grossarea ofwall)gt 01) caused the flexural cracks to closewhen thelateral load was removed In Options-2ndash4 small permanentdeformation (residual displacement) is observed This isbecause of the plastification of BRBs as well as transfer of themoment demand from shear wall to columns in the form ofaxial push-pull
8 Conclusions
(i) In this study different options of location of BRBsare investigated for a 40-story case study buildingThe locations of BRBs are identified based on theDBE elastic racking shear deformation and shear andbending moment demands in dominant 2nd and 3rdmodes NLRHA is then performed for seven sets ofspectrally matched target time histories and resultsare compared for different options
(ii) In all options shear force demands bending momentat mid height displacement demand racking sheardeformation demand and rotation demand in cou-pling beams are reduced by 10 45 45 45 and40 respectively in comparison to the controlledstructure
(iii) Rotational demand in the core wall at base level isreduced by 99 57 and 93 in Option-2 Option-3 and Option-4 respectively in comparison toOption-1Whereas energy dissipated by the core wallis reduced by around 250 in the corewall in compar-ison to the controlled structure Rotational demandand energy dissipation are measure of damage in thecore wall Thus damage can be significantly reducedby installation of BRBs
14 Shock and Vibration
(iv) All BRBs options are effective for bending momentreduction at mid height displacement and rackingshear deformation demands along the wall heightand rotation demand at the base of the wall and incoupling beams above the mid height of the build-ing However Option-4 in which BRBs are installedbetween peripheral columns and central corewall andcut in shear walls based on the maximum shear forceand bending moment leads to the highest reductionThis is because of the early yielding of the interiorbraces
(v) Thiswork is equally important for academia and prac-tising engineers especially those working in the fieldof performance based design of the high-rise build-ings in the commercial consultancy This will helpthem to locate BRBs at appropriate locations whiledesigning their buildings in an optimal way
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] International Conference of Building Officials Uniform Build-ing Code vol 2 International Conference of Building OfficialsWhittier Calif USA 1997
[2] J Maffei and N Yuen ldquoSeismic performance and designrequirements for high rise buildingsrdquo Structural Magazine pp28ndash32 2007
[3] J P Moehle ldquoPerformance-based seismic design of tall build-ings in the USrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[4] CEN EC8 Design of Structures for Earthquake ResistanceEuropean Committee for Standardization Brussels Belgium2004
[5] NZS 3101 Part 12006 Concrete Structures Standards NewZealand Standards New Zealand Wellington New Zealand2006
[6] T Paulay and M J N Priestley Seismic Design of ReinforcedConcrete and Masonry Buildings Wiley Hoboken NJ USA1992
[7] M Panagiotou J I Restrepo and J P Conte ldquoShake table test ofa 7-story full scale reinforced concrete structural wall buildingslice phase I rectangular wallrdquo Report SSRP 07-07 Departmentof Structural Engineering University of California San DiegoSan Diego Calif USA 2007
[8] Canadian Standard Association CSA Standard A233-04Design of Concrete Structures Canadian Standard AssociationRexdale Canada 2005
[9] R Klemencic J A Fry J D Hooper and B G MorgenldquoPerformance-based design of ductile concrete core wall build-ingsmdashissues to consider before detailed analysisrdquoTheStructuralDesign of Tall and Special Buildings vol 16 no 5 pp 599ndash6142007
[10] R Klemencic ldquoPerformance based seismic designmdashrisingrdquoStructural Magazine 2008 httpwwwstructuremagorgwp-contentuploads201408C-StructuralPractices-Klemencic-June081pdf
[11] A Zekioglu M Willford L Jin and M Melek ldquoCase studyusing the Los Angeles tall buildings structural design councilguidelines 40-storey concrete core wall buildingrdquo StructuralDesign of Tall and Special Buildings vol 16 no 5 pp 583ndash5972007
[12] B R Rad and P Adebar ldquoDynamic shear amplification inhigh-rise concrete walls effect of multiple flexural hinges andshear crackingrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[13] M Panagiotou and J I Restrepo ldquoDual-plastic hinge designconcept for reducing higher-mode effects on high-rise can-tilever wall buildingsrdquo Earthquake Engineering and StructuralDynamics vol 38 no 12 pp 1359ndash1380 2009
[14] M Ahmed and P Warnitchai ldquoReduction of inelastic seismicdemands by inducing plastic hinges at effective locationsrdquoin Proceedings of the 3rd Asian Conference on EarthquakeEngineering (ACEE rsquo10) Bangkok Thailand December 2010
[15] A Munir and P Warnitchai ldquoThe cause of unproportion-ately large higher mode contributions in the inelastic seismicresponses of high-rise core-wall buildingsrdquo Earthquake Engi-neering amp Structural Dynamics vol 41 no 15 pp 2195ndash22142012
[16] A Munir and P Warnitchai ldquoOptimal reduction of inelasticseismic demands in high-rise reinforced concrete core wallbuildings using energy-dissipating devicesrdquo Structural Design ofTall and Special Buildings vol 22 no 7 pp 543ndash568 2013
[17] M C Constantinou and M D Symans ldquoExperimental andanalytical investigation of seismic response of structures withsupplemental fluid viscous dampersrdquo NCEER Reports 92-0032State University of New York at Buffalo Buffalo NY USA 1992
[18] A SWhittaker V V Bertero C LThompson and L J AlonsoldquoSeismic testing of steel plate energy dissipation devicesrdquoEarthquake Spectra vol 7 no 4 pp 563ndash604 1991
[19] G W Housner L A Bergman T K Caughey et al ldquoStruc-tural control past present and futurerdquo Journal of EngineeringMechanics vol 123 no 9 pp 897ndash971 1997
[20] M D Symans F A Charney A S Whittaker et al ldquoEnergydissipation systems for seismic applications current practiceand recent developmentsrdquo Journal of Structural Engineering vol134 no 1 pp 3ndash21 2008
[21] C J Black N Makris and I D Aiken ldquoComponent testingseismic evaluation and characterization of buckling-restrainedbracesrdquo Journal of Structural Engineering vol 130 no 6 pp880ndash894 2004
[22] S Keten A performance based approach for seismic designwith hysteretic dampers [MS thesis] Massachusetts Institute ofTechnology (MIT) 2006 httpdspacemitedubitstreamhan-dle172113459571252112-MITpdfsequence=2
[23] N Anwar J A Sy T H Aung and D Rayamajhi ldquoFirstapplication of buckling restraint brace system in Philippines ina 50-story building with ductile core wall and PT slab systemrdquoin Proceedings of the 9th International Conference on UrbanEarthquake Engineering and the 4th Asia Conference on Earth-quake Engineering Tokyo Institute of Technology Tokyo JapanMarch 2012
[24] Computers and Structures Inc ETABS Extended 3D Analysis ofBuilding Systems Software Nonlinear Version 900 Computersand Structures Inc Berkeley Calif USA 2005
[25] Computers and Structures Perform 3D Nonlinear Analysis andPerformance Assessment for 3D Structures User Guide Version 4Computers and Structures Berkeley Calif USA 2006
Shock and Vibration 15
[26] J W Wallace and J P Moehle ldquoDuctility and detailing require-ments of bearing wall buildingsrdquo Journal of Structural Engineer-ing vol 118 no 6 pp 1625ndash1644 1992
[27] P Adebar A M M Ibrahim and M Bryson ldquoTest of high-risecore wall effective stiffness for seismic analysisrdquo ACI StructuralJournal vol 104 no 5 pp 549ndash559 2007
[28] FEMA ldquoPrestandard and commentary for the seismic rehabil-itation of buildingsrdquo FEMA 356 Federal Emergency Manage-ment Agency Washington DC USA 2000
[29] LATBDSC An Alternative Procedure for Seismic Analysis andDesign of Tall Buildings Located in Los Angeles Region A Con-sensus Document Los Angeles Tall Buildings and StructuralDesign Council 2008
[30] PEERNGAData Base Pacific Earthquake Engineering Research(PEER) University of California Berkeley Calif USA 2005httppeerberkeleyedunga
[31] COSMOS Data Base ldquoConsortium of organization for strong-motion observation systemsrdquo Tech Rep University of Cali-fornia Berkeley Calif USA 1999ndash2007 httpwwwcosmos-eqorgscriptsdefaultplx
[32] K Lilhanand and W S Tseng ldquoDevelopment and applicationof realistic earthquake time histories compatible with multipledamping design spectrardquo in Proceedings of the 9th World Con-ference on Earthquake Engineering Tokyo Japan August 1988
[33] J Hancock J Watson-Lamprey N A Abrahamson et al ldquoAnimproved method of matching response spectra of recordedearthquake ground motion using waveletsrdquo Journal of Earth-quake Engineering vol 10 no 1 pp 67ndash89 2006
[34] J B Mander M J N Priestley and R Park ldquoTheoreticalstress-strain model for confined concreterdquo Journal of StructuralEngineering New York vol 114 no 8 pp 1804ndash1826 1988
[35] CTBUH Seismic Working Group CTBUH Recommendationsfor the Seismic Design of High-Rise Buildings A ConsensusDocument 2008
[36] N Satake K-I Suda T Arakawa A Sasaki and Y TamuraldquoDamping evaluation using full-scale data of buildings inJapanrdquo Journal of Structural Engineering vol 129 no 4 pp 470ndash477 2003
[37] Q Xie ldquoState of the art of buckling-restrained braces in AsiardquoJournal of Constructional Steel Research vol 61 no 6 pp 727ndash748 2005
[38] P Clark K Kasai I Aiken E Ko and I Kimura ldquoDesign proce-dures for buildings incorporating hysteretic energy dissipatingdevicesrdquo in Proceedings of the 68th Annual Convention Struc-tural Engineers Association of California Santa Barbara CalifUSA October 1999
[39] D Vafaei and R Eskandari ldquoSeismic response of mega buck-ling-restrained braces subjected to fling-step and forward-directivity near-fault ground motionsrdquo Structural Design of Talland Special Buildings vol 24 no 9 pp 672ndash686 2015
[40] L Di Sarno and A S Elnashai ldquoBracing systems for seismicretrofitting of steel framesrdquo Journal of Constructional SteelResearch vol 65 no 2 pp 452ndash465 2009
[41] A Dutta and R O Hamburger ldquoCase study of A 40-Storeybuckling-restrained braced frame building located in LosAnge-lesrdquo The Structural Design of Tall and Special Buildings vol 19no 1-2 pp 77ndash93 2010
[42] Rutherford amp Chekene ldquoPerform nonlinear component mod-elling of star seismic powercat BRBsrdquo Report to Star SeismicLLC Star Seismic LLC 2011
[43] P Dusicka A M Itani and I G Buckle ldquoCyclic response ofplate steels under large inelastic strainsrdquo Journal of Construc-tional Steel Research vol 63 no 2 pp 156ndash164 2007
[44] S A Razavi M E Shemshadian S R Mirghaderi and SAhlehagh ldquoSeismic design of buckling restrained braced frameswith reduced core lengthrdquo in Proceedings of the The StructuralEngineers World Congress Cernobbio Italy 2011
[45] S A Razavi S R Mirghaderi A Hosseini and M EShemshadian ldquoReduced length buckling restrained brace usingsteel plates as restraining segmentrdquo in Proceedings of the 15thWorld Conference on Earthquake Engineering Lisboa PurtagalSeptember 2012
[46] M E Shemshadian S A Razavi S R Mirghaderi A Hosseiniand M K Mohammadi ldquoThe advantages of reducing thelength of yielding segment in seismic performance of bucklingrestrained braced framesrdquo inProceedings of the 6th InternationalConference of Seismology and Earthquake Engineering TehranIran 2011
[47] N Ma B Wu J Zhao H Li J Ou andW Yang ldquoFull scale testof all-steel buckling restrained bracesrdquo in Proceedings of the 14thWorld Conference on Earthquake Engineering Beijing ChinaOctober 2008
[48] L Di Sarno and G Manfredi ldquoSeismic retrofitting of existingRC frames with buckling restrained bracesrdquo in Proceedings ofthe Improving the Seismic Performance of Existing Buildingsand Other Structures pp 741ndash752 San Francisco Calif USADecember 2009
[49] S Ahlehagh Improvement of the special concentrically bracedsteel frames behaviour by employing balanced braces [MSthesis] University of Tehran Tehran Iran 2008
[50] R Tremblay P Bolduc R Neville and R DeVall ldquoSeismic test-ing and performance of buckling-restrained bracing systemsrdquoCanadian Journal of Civil Engineering vol 33 no 2 pp 183ndash1982006
Figure 9 Arrangement of the exterior BRBs at locations of maximum DBE elastic racking shear deformation in 2nd and 3rd mode andinterior BRBs at locations of maximum DBE elastic shear demands in 2nd and 3rd mode (Option-3)
Option-1 Option-2 andOption-3 are also suitable for mode-1
The BRBs dissipate energy through axial tension andcompression To achieve maximum energy dissipation theBRBs should be placed at the proper locations and anglesEach BRB has been placed at an angle of approximately1205874 covering almost three stories for exterior brace and twostories for brace in cut in core wall These V-shaped BRBsconfigurations resemble the BRBs configuration used inmegabraced frames steel buildings reported in the previous studies[39ndash41] BRBs shall cross the slabs through purposely builtopenings provided in the slabs A horizontal drag elementis used from point where BRB connects to the column tothe central core wall to take care of the horizontal forcecomponent of the BRB axial force at column connection
53 Size of Buckling Restrained Braces Sizes of the BRBs havebeen selected by hit and trial using more rigorous nonlineartime history analyses (NLTHAs) using displacement-baseddesign approach Their size should neither be too large tobe uneconomical nor be too small to be ineffective The 119883-section of the braces between peripheral columns and centralcore wall is selected as 7500mm2 whereas it is 3750mm2for braces in cuts in core wall The buckling restrained bracesmanufactured by star seismic with normal yield strength of280MPa are used for braces between peripheral columnsand central core wall [42] However the low yield point-100(LYP100) steel core manufactured by Nippon Steel Corpora-tion Japan with specified yield strength of 100MPa is used
f
0DXDU
FY
FUO
FUH
KF
KO
Figure 10 Trilinear curve for BRBs
for braces in cut elements [22]The lowyield point steel bracesare used in cut in core wall to mainly achieve more energydissipation through the early yielding of the brace [43]
54 Modelling of Buckling Restrained Braces A BRB consistsof three components that is central yielding core brace endsmember connecting the central brace with the pin connec-tion and pin connection between brace and main structuralmembers The length of the exterior core brace is 45mwhereas length of the core brace in cut of core wall is 18mThese lengths are in the optimum range of 02ndash04 times thetotal length of the brace Several advantages such as simple
Shock and Vibration 9
minus4000
minus3000
minus2000
minus1000
0
1000
2000
3000
4000A
xial
forc
e ( k
N)
Axial def (m)
10E minus 0150E minus 0200E + 00minus50E minus 02
(a)
minus500
minus400
minus300
minus200
minus100
0
100
200
300
400
500
Axi
al fo
rce (
kN
)
Axial def (m)
20E
minus03
10E
minus03
00E
+00
minus30E
minus03
minus20E
minus03
minus10E
minus03
(b)
Figure 11 Typical cyclic response of BRBs obtained from the analysis (a) Exterior brace (b) interior brace
replacement lesser weight concrete elimination economyand easy erection process are associated with reduced lengthof the core brace [44ndash50] BRB has been modelled using theBRB compound component of the Perform-3D Such mem-ber is composed of three components that is (1) a BRB basiccomponent for main yielding brace (2) an elastic bar basiccomponent for member connecting brace with gusset plateand (3) a stiff end zone which accounts for the gusset platesand so forth at both ends of the member
The positive side (tension) of the trilinear curve to definethe force-deformation of the BRBs is shown in Figure 10 Itcan be seen that after yielding there are two lines such asbottom and top line The bottom line is used to simulate firstcyclic load and the top line is used to simulate full strainhardening The same behavior has been observed in testslike the hysteresis loop which can progressively grow in sizeThis is sometimes referred to as ldquoisotropic hardeningrdquo Thisleads to the component increase in strength under cyclic loadThe negative side of the curve shows a little variation due todifference in the values of compression and tensions FY FUO(FUO (T) = 105 FY FUO (C) = 104 FY) and FUH (FUO(T) = 134 FY FUO (C) = 151 FY) are yield strength strengthat first loading cycle and strength of the core brace afterfull hardening respectively DU (DU (T) = 07 DU (C) =07) is the deformation at FUO and DX (DX (T) = 004 LYCDX (C) = 004 LYC) is the maximum deformation of thebrace LYC is the length of the yielding core KO is theInitial stiffness of the core brace and KF (= 002KO) is theslope of third line [42] The strain hardening properties suchas deformation at FUO-FUH average are taken equal to 2times (LYC180) and deformation at FUH is taken as 35times (LYC180) The typical force-deformation relationshipfor exterior (between peripheral columns and core wall) andinterior BRB (in cut in core wall) obtained from NLRHAanalysis for a particular ground motion is shown in Figures11(a) and 11(b) respectivelyThese figures show that hysteresisloop is similar to the reported Clark et al 1999 [38] provingthat performing BRB element can capture the behaviour
appropriately The size of the elastic bar element is selectedsuch that it can safely carry maximum axial force in brace inelastic range to conform to the capacity design approach Stiffend zone is few times stiffer than the elastic bar element
6 Comparison of the Responses in DifferentOptions and Discussion on the Results
NLRHA is performed using seven spectrally matched timehistories Different response quantities such as displacementplastic hinge rotations in coupling beams and core wall sheardeformation angle (story racking shear deformation) bend-ing moment shear force and energy demands are obtainedfrom this analysisThe plastic rotations are calculated bymul-tiplying the average curvature of the wall at mid height withthe plastic hinge length The mean value of different quan-tities obtained from seven ground motions are shown anddiscussed in following paragraphs
Shear demands obtained from four options are shownin Figure 12(a) Shear demand pattern and magnitude aresimilar in all options Moment demands obtained from fouroptions are shown in Figure 12(b) The moment demand atthe base is similar in all four options because this is clippedto the flexural strength of the plastic hinge at the base of thewall However it is reduced along the wall height by 30 35and 40 in Option-2 Option-3 and Option-4 respectivelyin comparison to that in 1st optionThe reduction inmomentdemand is significant in all options This will help to avoidreinforcement congestion in the wall near mid height
Displacement demands obtained from four options areshown in Figure 13(a) Displacement demand pattern is simi-lar for all options However displacement demand is reducedalong thewall height by 40 40 and 60 inOption-2 Option-3 and Option-4 respectively in comparison to that in 1stoption Racking shear deformation demands obtained fromfour options are shown in Figure 13(b) The racking sheardeformation demand patterns are similar for all four optionsHowever racking shear deformation demands are reduced
10 Shock and Vibration
minus5
0
5
10
15
20
25
30
35
40
0 50000 100000 150000
Leve
l
Shear force (kN)
Option-1Option-2
Option-3Option-4
(a)
minus5
0
5
10
15
20
25
30
35
40
Leve
l
0 1 2 3
Option-1Option-2
Option-3Option-4
Bending moment (kNmiddotm times 106)
(b)
Figure 12 MCE inelastic shear and moment demands in different options (a) Shear (b) moment
0 05 1 15 2 25Displacement (m)minus5
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(a)
0 001 002 003 004Racking shear deformation ratio
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(b)
Figure 13 MCE inelastic displacement and racking deformation demands in different options (a) Displacement (b) racking sheardeformation angle
along the wall height by 40 40 and 65 in Option-2Option-3 and Option-4 respectively in comparison to thatin 1st option This is significant reduction Racking sheardeformations of 0036 in the controlled structures are reducedto 0023 which is well within the limit of 003 set by [29]LATBSDC 2008 for the MCE level earthquake
Rotational demands in the core wall at the base level aswell as in coupling beams along the height are shown in Fig-ures 14(a) and 14(b) respectivelyThe rotation demand in thewall is calculated by multiplying the average curvature at themid height of the inelastic wall element by height of the wallThe comparison shows that themaximum rotational demand
at the base of the wall is reduced by 99 57 and 93 inOption-2Option-3 andOption-4 respectively in comparison to thatin 1st option This is strong indication that damage at thebase of the wall shall be reduced to half and consequentlyextent of repair shall be small and hence cheap in case ofsevere MCE events such as DBE and MCE level earthquakeThe rotational demands in coupling beams are reduced by52 40 and 35 respectively above the half height level forOption-2 Option-3 and Option-4 respectively in compar-ison to 1st option However rotation demand remained thesame in the lower half portion of the building for all options
Energy dissipated by core wall coupling beams andbuckling restrained braces have been compared in Figures15(a)ndash15(d) respectively for Option-1 Option-2 Option-3 and Option-4 respectively This is energy dissipated inpercentage of the total energy demand in the structure Thetotal energy demand is sum of the kinetic energy elasticstrain energy energy dissipated by elastic modal dampingand energy dissipation by damage in structural elements suchas core wall coupling beams and BRBs About 83 9292 and 90 energy have been dissipated by elastic modaland inelastic damping in Option-1 to Option-4 respectivelyThe energy dissipation by modal elastic damping to the totalenergy demands is 50 37 35 and 33 respectively inOption-1 to Option-4 respectivelyThe energy dissipation bycore wall at the base to the total energy demands is 22 66 and 6 inOption-1 to Option-4 respectivelyThe energydissipation by coupling beams to the total energy demands isapproximately 10 4 5 and 6 in Option-1 to Option-4 respectively The energy dissipation by BRBs to the total
energy demands is 0 45 45 and 45 respectively inOption-1 to Option-4
7 Effects of BRBs on Axial Loads Shearand Moment of Columns and PermanentDeformation due to BRBs Plastification
Effects of BRBs on axial loads of columns and permanentdeformation due to BRBs plastification have been discussedin this section The axial load envelope in a typical columnfor Options-1ndash4 is shown in the Figure 16 The magnitude ofaxial load is same for Options-2ndash4 (with BRBs) and is twicethan that in Option-1 (controlled structure) This is due tothe outrigger effect created by the connection of columnsand core wall through BRBs Some core wall moment hasbeen resisted by the development of axial push-pull in thecolumns Furthermore the shape of the axial load envelopeis smooth in case of Option-1 whereas it is jagged at thelocations of the BRBs forOptions-2ndash4Themoment envelopeand shear envelope for one typical column are shown inFigures 17(a) and 17(b) respectively It shows that momentand shear have been reduced at the ground level in Options-2ndash4 in comparison to Option-1 whereas these remain almostthe same at upper portions The extra moment and shearat the ground level in Options-1ndash4 is due to the transfer ofmoment and shear to the columns when core wall yields
To better understand the permanent deformation in thestructure due to BRBs plastification cyclic pushover analysisin firstmode is performedusing target displacement obtainedfrom NLTHA for all cases The cyclic base shear versus top
12 Shock and Vibration
Option-1
0
20
40
60
80
100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 53478kNmiddotm
(a)
Option-2
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 73328kNmiddotm
(b)
Option-3
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80 90
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 71449kNmiddotm
(c)
Option-4
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 69558kNmiddotm
(d)
Figure 15 Inelastic energy demands in structural components (a) to (d) For Option-1 to Option-4 respectively
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus20000 minus10000 0
Leve
l
Axial load (kN)
Option-1Option-2
Option-3Option-4
Figure 16 Axial load envelope in one typical column
Shock and Vibration 13
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus15000 0 15000 30000
Leve
l
minus5
0
5
10
15
20
25
30
35
40
Leve
l
Moment (kNmiddotm)
minus1200 minus800 minus400 0 400 800 1200
Shear (kN)
Option-1Option-2
Option-3Option-4
Option-1Option-2
Option-3Option-4
Figure 17 Moment and shear envelope in one typical column
minus20 minus10 00 10 20
Base
shea
r (kN
)
Top displacement (m)
Option-1Option-2
Option-3Option-4
300E + 04
200E + 04
100E + 04
000E + 00
minus100E + 04
minus200E + 04
minus300E + 04
Figure 18 Base shear versus top displacement relationship in firstmode load pattern
displacement is compared in Figure 18 It can be seen that thiscurve is flag shaped for Option-1 whereas it is bilinear pinch-ing type in Options-2ndash4There is no permanent deformationin controlled structure and flag shaped hysteresis behaviouris observed The same behaviour was observed during testconducted on a large-scale model of a concrete shear wallfrom the core of a high-rise building in the study of Adebar etal [27] The combination of low percentage of vertical rein-forcement and large axial compression force due to gravity
loads (axial force(concrete 28 days cylinder strength times grossarea ofwall)gt 01) caused the flexural cracks to closewhen thelateral load was removed In Options-2ndash4 small permanentdeformation (residual displacement) is observed This isbecause of the plastification of BRBs as well as transfer of themoment demand from shear wall to columns in the form ofaxial push-pull
8 Conclusions
(i) In this study different options of location of BRBsare investigated for a 40-story case study buildingThe locations of BRBs are identified based on theDBE elastic racking shear deformation and shear andbending moment demands in dominant 2nd and 3rdmodes NLRHA is then performed for seven sets ofspectrally matched target time histories and resultsare compared for different options
(ii) In all options shear force demands bending momentat mid height displacement demand racking sheardeformation demand and rotation demand in cou-pling beams are reduced by 10 45 45 45 and40 respectively in comparison to the controlledstructure
(iii) Rotational demand in the core wall at base level isreduced by 99 57 and 93 in Option-2 Option-3 and Option-4 respectively in comparison toOption-1Whereas energy dissipated by the core wallis reduced by around 250 in the corewall in compar-ison to the controlled structure Rotational demandand energy dissipation are measure of damage in thecore wall Thus damage can be significantly reducedby installation of BRBs
14 Shock and Vibration
(iv) All BRBs options are effective for bending momentreduction at mid height displacement and rackingshear deformation demands along the wall heightand rotation demand at the base of the wall and incoupling beams above the mid height of the build-ing However Option-4 in which BRBs are installedbetween peripheral columns and central corewall andcut in shear walls based on the maximum shear forceand bending moment leads to the highest reductionThis is because of the early yielding of the interiorbraces
(v) Thiswork is equally important for academia and prac-tising engineers especially those working in the fieldof performance based design of the high-rise build-ings in the commercial consultancy This will helpthem to locate BRBs at appropriate locations whiledesigning their buildings in an optimal way
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] International Conference of Building Officials Uniform Build-ing Code vol 2 International Conference of Building OfficialsWhittier Calif USA 1997
[2] J Maffei and N Yuen ldquoSeismic performance and designrequirements for high rise buildingsrdquo Structural Magazine pp28ndash32 2007
[3] J P Moehle ldquoPerformance-based seismic design of tall build-ings in the USrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[4] CEN EC8 Design of Structures for Earthquake ResistanceEuropean Committee for Standardization Brussels Belgium2004
[5] NZS 3101 Part 12006 Concrete Structures Standards NewZealand Standards New Zealand Wellington New Zealand2006
[6] T Paulay and M J N Priestley Seismic Design of ReinforcedConcrete and Masonry Buildings Wiley Hoboken NJ USA1992
[7] M Panagiotou J I Restrepo and J P Conte ldquoShake table test ofa 7-story full scale reinforced concrete structural wall buildingslice phase I rectangular wallrdquo Report SSRP 07-07 Departmentof Structural Engineering University of California San DiegoSan Diego Calif USA 2007
[8] Canadian Standard Association CSA Standard A233-04Design of Concrete Structures Canadian Standard AssociationRexdale Canada 2005
[9] R Klemencic J A Fry J D Hooper and B G MorgenldquoPerformance-based design of ductile concrete core wall build-ingsmdashissues to consider before detailed analysisrdquoTheStructuralDesign of Tall and Special Buildings vol 16 no 5 pp 599ndash6142007
[10] R Klemencic ldquoPerformance based seismic designmdashrisingrdquoStructural Magazine 2008 httpwwwstructuremagorgwp-contentuploads201408C-StructuralPractices-Klemencic-June081pdf
[11] A Zekioglu M Willford L Jin and M Melek ldquoCase studyusing the Los Angeles tall buildings structural design councilguidelines 40-storey concrete core wall buildingrdquo StructuralDesign of Tall and Special Buildings vol 16 no 5 pp 583ndash5972007
[12] B R Rad and P Adebar ldquoDynamic shear amplification inhigh-rise concrete walls effect of multiple flexural hinges andshear crackingrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[13] M Panagiotou and J I Restrepo ldquoDual-plastic hinge designconcept for reducing higher-mode effects on high-rise can-tilever wall buildingsrdquo Earthquake Engineering and StructuralDynamics vol 38 no 12 pp 1359ndash1380 2009
[14] M Ahmed and P Warnitchai ldquoReduction of inelastic seismicdemands by inducing plastic hinges at effective locationsrdquoin Proceedings of the 3rd Asian Conference on EarthquakeEngineering (ACEE rsquo10) Bangkok Thailand December 2010
[15] A Munir and P Warnitchai ldquoThe cause of unproportion-ately large higher mode contributions in the inelastic seismicresponses of high-rise core-wall buildingsrdquo Earthquake Engi-neering amp Structural Dynamics vol 41 no 15 pp 2195ndash22142012
[16] A Munir and P Warnitchai ldquoOptimal reduction of inelasticseismic demands in high-rise reinforced concrete core wallbuildings using energy-dissipating devicesrdquo Structural Design ofTall and Special Buildings vol 22 no 7 pp 543ndash568 2013
[17] M C Constantinou and M D Symans ldquoExperimental andanalytical investigation of seismic response of structures withsupplemental fluid viscous dampersrdquo NCEER Reports 92-0032State University of New York at Buffalo Buffalo NY USA 1992
[18] A SWhittaker V V Bertero C LThompson and L J AlonsoldquoSeismic testing of steel plate energy dissipation devicesrdquoEarthquake Spectra vol 7 no 4 pp 563ndash604 1991
[19] G W Housner L A Bergman T K Caughey et al ldquoStruc-tural control past present and futurerdquo Journal of EngineeringMechanics vol 123 no 9 pp 897ndash971 1997
[20] M D Symans F A Charney A S Whittaker et al ldquoEnergydissipation systems for seismic applications current practiceand recent developmentsrdquo Journal of Structural Engineering vol134 no 1 pp 3ndash21 2008
[21] C J Black N Makris and I D Aiken ldquoComponent testingseismic evaluation and characterization of buckling-restrainedbracesrdquo Journal of Structural Engineering vol 130 no 6 pp880ndash894 2004
[22] S Keten A performance based approach for seismic designwith hysteretic dampers [MS thesis] Massachusetts Institute ofTechnology (MIT) 2006 httpdspacemitedubitstreamhan-dle172113459571252112-MITpdfsequence=2
[23] N Anwar J A Sy T H Aung and D Rayamajhi ldquoFirstapplication of buckling restraint brace system in Philippines ina 50-story building with ductile core wall and PT slab systemrdquoin Proceedings of the 9th International Conference on UrbanEarthquake Engineering and the 4th Asia Conference on Earth-quake Engineering Tokyo Institute of Technology Tokyo JapanMarch 2012
[24] Computers and Structures Inc ETABS Extended 3D Analysis ofBuilding Systems Software Nonlinear Version 900 Computersand Structures Inc Berkeley Calif USA 2005
[25] Computers and Structures Perform 3D Nonlinear Analysis andPerformance Assessment for 3D Structures User Guide Version 4Computers and Structures Berkeley Calif USA 2006
Shock and Vibration 15
[26] J W Wallace and J P Moehle ldquoDuctility and detailing require-ments of bearing wall buildingsrdquo Journal of Structural Engineer-ing vol 118 no 6 pp 1625ndash1644 1992
[27] P Adebar A M M Ibrahim and M Bryson ldquoTest of high-risecore wall effective stiffness for seismic analysisrdquo ACI StructuralJournal vol 104 no 5 pp 549ndash559 2007
[28] FEMA ldquoPrestandard and commentary for the seismic rehabil-itation of buildingsrdquo FEMA 356 Federal Emergency Manage-ment Agency Washington DC USA 2000
[29] LATBDSC An Alternative Procedure for Seismic Analysis andDesign of Tall Buildings Located in Los Angeles Region A Con-sensus Document Los Angeles Tall Buildings and StructuralDesign Council 2008
[30] PEERNGAData Base Pacific Earthquake Engineering Research(PEER) University of California Berkeley Calif USA 2005httppeerberkeleyedunga
[31] COSMOS Data Base ldquoConsortium of organization for strong-motion observation systemsrdquo Tech Rep University of Cali-fornia Berkeley Calif USA 1999ndash2007 httpwwwcosmos-eqorgscriptsdefaultplx
[32] K Lilhanand and W S Tseng ldquoDevelopment and applicationof realistic earthquake time histories compatible with multipledamping design spectrardquo in Proceedings of the 9th World Con-ference on Earthquake Engineering Tokyo Japan August 1988
[33] J Hancock J Watson-Lamprey N A Abrahamson et al ldquoAnimproved method of matching response spectra of recordedearthquake ground motion using waveletsrdquo Journal of Earth-quake Engineering vol 10 no 1 pp 67ndash89 2006
[34] J B Mander M J N Priestley and R Park ldquoTheoreticalstress-strain model for confined concreterdquo Journal of StructuralEngineering New York vol 114 no 8 pp 1804ndash1826 1988
[35] CTBUH Seismic Working Group CTBUH Recommendationsfor the Seismic Design of High-Rise Buildings A ConsensusDocument 2008
[36] N Satake K-I Suda T Arakawa A Sasaki and Y TamuraldquoDamping evaluation using full-scale data of buildings inJapanrdquo Journal of Structural Engineering vol 129 no 4 pp 470ndash477 2003
[37] Q Xie ldquoState of the art of buckling-restrained braces in AsiardquoJournal of Constructional Steel Research vol 61 no 6 pp 727ndash748 2005
[38] P Clark K Kasai I Aiken E Ko and I Kimura ldquoDesign proce-dures for buildings incorporating hysteretic energy dissipatingdevicesrdquo in Proceedings of the 68th Annual Convention Struc-tural Engineers Association of California Santa Barbara CalifUSA October 1999
[39] D Vafaei and R Eskandari ldquoSeismic response of mega buck-ling-restrained braces subjected to fling-step and forward-directivity near-fault ground motionsrdquo Structural Design of Talland Special Buildings vol 24 no 9 pp 672ndash686 2015
[40] L Di Sarno and A S Elnashai ldquoBracing systems for seismicretrofitting of steel framesrdquo Journal of Constructional SteelResearch vol 65 no 2 pp 452ndash465 2009
[41] A Dutta and R O Hamburger ldquoCase study of A 40-Storeybuckling-restrained braced frame building located in LosAnge-lesrdquo The Structural Design of Tall and Special Buildings vol 19no 1-2 pp 77ndash93 2010
[42] Rutherford amp Chekene ldquoPerform nonlinear component mod-elling of star seismic powercat BRBsrdquo Report to Star SeismicLLC Star Seismic LLC 2011
[43] P Dusicka A M Itani and I G Buckle ldquoCyclic response ofplate steels under large inelastic strainsrdquo Journal of Construc-tional Steel Research vol 63 no 2 pp 156ndash164 2007
[44] S A Razavi M E Shemshadian S R Mirghaderi and SAhlehagh ldquoSeismic design of buckling restrained braced frameswith reduced core lengthrdquo in Proceedings of the The StructuralEngineers World Congress Cernobbio Italy 2011
[45] S A Razavi S R Mirghaderi A Hosseini and M EShemshadian ldquoReduced length buckling restrained brace usingsteel plates as restraining segmentrdquo in Proceedings of the 15thWorld Conference on Earthquake Engineering Lisboa PurtagalSeptember 2012
[46] M E Shemshadian S A Razavi S R Mirghaderi A Hosseiniand M K Mohammadi ldquoThe advantages of reducing thelength of yielding segment in seismic performance of bucklingrestrained braced framesrdquo inProceedings of the 6th InternationalConference of Seismology and Earthquake Engineering TehranIran 2011
[47] N Ma B Wu J Zhao H Li J Ou andW Yang ldquoFull scale testof all-steel buckling restrained bracesrdquo in Proceedings of the 14thWorld Conference on Earthquake Engineering Beijing ChinaOctober 2008
[48] L Di Sarno and G Manfredi ldquoSeismic retrofitting of existingRC frames with buckling restrained bracesrdquo in Proceedings ofthe Improving the Seismic Performance of Existing Buildingsand Other Structures pp 741ndash752 San Francisco Calif USADecember 2009
[49] S Ahlehagh Improvement of the special concentrically bracedsteel frames behaviour by employing balanced braces [MSthesis] University of Tehran Tehran Iran 2008
[50] R Tremblay P Bolduc R Neville and R DeVall ldquoSeismic test-ing and performance of buckling-restrained bracing systemsrdquoCanadian Journal of Civil Engineering vol 33 no 2 pp 183ndash1982006
Figure 11 Typical cyclic response of BRBs obtained from the analysis (a) Exterior brace (b) interior brace
replacement lesser weight concrete elimination economyand easy erection process are associated with reduced lengthof the core brace [44ndash50] BRB has been modelled using theBRB compound component of the Perform-3D Such mem-ber is composed of three components that is (1) a BRB basiccomponent for main yielding brace (2) an elastic bar basiccomponent for member connecting brace with gusset plateand (3) a stiff end zone which accounts for the gusset platesand so forth at both ends of the member
The positive side (tension) of the trilinear curve to definethe force-deformation of the BRBs is shown in Figure 10 Itcan be seen that after yielding there are two lines such asbottom and top line The bottom line is used to simulate firstcyclic load and the top line is used to simulate full strainhardening The same behavior has been observed in testslike the hysteresis loop which can progressively grow in sizeThis is sometimes referred to as ldquoisotropic hardeningrdquo Thisleads to the component increase in strength under cyclic loadThe negative side of the curve shows a little variation due todifference in the values of compression and tensions FY FUO(FUO (T) = 105 FY FUO (C) = 104 FY) and FUH (FUO(T) = 134 FY FUO (C) = 151 FY) are yield strength strengthat first loading cycle and strength of the core brace afterfull hardening respectively DU (DU (T) = 07 DU (C) =07) is the deformation at FUO and DX (DX (T) = 004 LYCDX (C) = 004 LYC) is the maximum deformation of thebrace LYC is the length of the yielding core KO is theInitial stiffness of the core brace and KF (= 002KO) is theslope of third line [42] The strain hardening properties suchas deformation at FUO-FUH average are taken equal to 2times (LYC180) and deformation at FUH is taken as 35times (LYC180) The typical force-deformation relationshipfor exterior (between peripheral columns and core wall) andinterior BRB (in cut in core wall) obtained from NLRHAanalysis for a particular ground motion is shown in Figures11(a) and 11(b) respectivelyThese figures show that hysteresisloop is similar to the reported Clark et al 1999 [38] provingthat performing BRB element can capture the behaviour
appropriately The size of the elastic bar element is selectedsuch that it can safely carry maximum axial force in brace inelastic range to conform to the capacity design approach Stiffend zone is few times stiffer than the elastic bar element
6 Comparison of the Responses in DifferentOptions and Discussion on the Results
NLRHA is performed using seven spectrally matched timehistories Different response quantities such as displacementplastic hinge rotations in coupling beams and core wall sheardeformation angle (story racking shear deformation) bend-ing moment shear force and energy demands are obtainedfrom this analysisThe plastic rotations are calculated bymul-tiplying the average curvature of the wall at mid height withthe plastic hinge length The mean value of different quan-tities obtained from seven ground motions are shown anddiscussed in following paragraphs
Shear demands obtained from four options are shownin Figure 12(a) Shear demand pattern and magnitude aresimilar in all options Moment demands obtained from fouroptions are shown in Figure 12(b) The moment demand atthe base is similar in all four options because this is clippedto the flexural strength of the plastic hinge at the base of thewall However it is reduced along the wall height by 30 35and 40 in Option-2 Option-3 and Option-4 respectivelyin comparison to that in 1st optionThe reduction inmomentdemand is significant in all options This will help to avoidreinforcement congestion in the wall near mid height
Displacement demands obtained from four options areshown in Figure 13(a) Displacement demand pattern is simi-lar for all options However displacement demand is reducedalong thewall height by 40 40 and 60 inOption-2 Option-3 and Option-4 respectively in comparison to that in 1stoption Racking shear deformation demands obtained fromfour options are shown in Figure 13(b) The racking sheardeformation demand patterns are similar for all four optionsHowever racking shear deformation demands are reduced
10 Shock and Vibration
minus5
0
5
10
15
20
25
30
35
40
0 50000 100000 150000
Leve
l
Shear force (kN)
Option-1Option-2
Option-3Option-4
(a)
minus5
0
5
10
15
20
25
30
35
40
Leve
l
0 1 2 3
Option-1Option-2
Option-3Option-4
Bending moment (kNmiddotm times 106)
(b)
Figure 12 MCE inelastic shear and moment demands in different options (a) Shear (b) moment
0 05 1 15 2 25Displacement (m)minus5
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(a)
0 001 002 003 004Racking shear deformation ratio
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(b)
Figure 13 MCE inelastic displacement and racking deformation demands in different options (a) Displacement (b) racking sheardeformation angle
along the wall height by 40 40 and 65 in Option-2Option-3 and Option-4 respectively in comparison to thatin 1st option This is significant reduction Racking sheardeformations of 0036 in the controlled structures are reducedto 0023 which is well within the limit of 003 set by [29]LATBSDC 2008 for the MCE level earthquake
Rotational demands in the core wall at the base level aswell as in coupling beams along the height are shown in Fig-ures 14(a) and 14(b) respectivelyThe rotation demand in thewall is calculated by multiplying the average curvature at themid height of the inelastic wall element by height of the wallThe comparison shows that themaximum rotational demand
at the base of the wall is reduced by 99 57 and 93 inOption-2Option-3 andOption-4 respectively in comparison to thatin 1st option This is strong indication that damage at thebase of the wall shall be reduced to half and consequentlyextent of repair shall be small and hence cheap in case ofsevere MCE events such as DBE and MCE level earthquakeThe rotational demands in coupling beams are reduced by52 40 and 35 respectively above the half height level forOption-2 Option-3 and Option-4 respectively in compar-ison to 1st option However rotation demand remained thesame in the lower half portion of the building for all options
Energy dissipated by core wall coupling beams andbuckling restrained braces have been compared in Figures15(a)ndash15(d) respectively for Option-1 Option-2 Option-3 and Option-4 respectively This is energy dissipated inpercentage of the total energy demand in the structure Thetotal energy demand is sum of the kinetic energy elasticstrain energy energy dissipated by elastic modal dampingand energy dissipation by damage in structural elements suchas core wall coupling beams and BRBs About 83 9292 and 90 energy have been dissipated by elastic modaland inelastic damping in Option-1 to Option-4 respectivelyThe energy dissipation by modal elastic damping to the totalenergy demands is 50 37 35 and 33 respectively inOption-1 to Option-4 respectivelyThe energy dissipation bycore wall at the base to the total energy demands is 22 66 and 6 inOption-1 to Option-4 respectivelyThe energydissipation by coupling beams to the total energy demands isapproximately 10 4 5 and 6 in Option-1 to Option-4 respectively The energy dissipation by BRBs to the total
energy demands is 0 45 45 and 45 respectively inOption-1 to Option-4
7 Effects of BRBs on Axial Loads Shearand Moment of Columns and PermanentDeformation due to BRBs Plastification
Effects of BRBs on axial loads of columns and permanentdeformation due to BRBs plastification have been discussedin this section The axial load envelope in a typical columnfor Options-1ndash4 is shown in the Figure 16 The magnitude ofaxial load is same for Options-2ndash4 (with BRBs) and is twicethan that in Option-1 (controlled structure) This is due tothe outrigger effect created by the connection of columnsand core wall through BRBs Some core wall moment hasbeen resisted by the development of axial push-pull in thecolumns Furthermore the shape of the axial load envelopeis smooth in case of Option-1 whereas it is jagged at thelocations of the BRBs forOptions-2ndash4Themoment envelopeand shear envelope for one typical column are shown inFigures 17(a) and 17(b) respectively It shows that momentand shear have been reduced at the ground level in Options-2ndash4 in comparison to Option-1 whereas these remain almostthe same at upper portions The extra moment and shearat the ground level in Options-1ndash4 is due to the transfer ofmoment and shear to the columns when core wall yields
To better understand the permanent deformation in thestructure due to BRBs plastification cyclic pushover analysisin firstmode is performedusing target displacement obtainedfrom NLTHA for all cases The cyclic base shear versus top
12 Shock and Vibration
Option-1
0
20
40
60
80
100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 53478kNmiddotm
(a)
Option-2
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 73328kNmiddotm
(b)
Option-3
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80 90
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 71449kNmiddotm
(c)
Option-4
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 69558kNmiddotm
(d)
Figure 15 Inelastic energy demands in structural components (a) to (d) For Option-1 to Option-4 respectively
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus20000 minus10000 0
Leve
l
Axial load (kN)
Option-1Option-2
Option-3Option-4
Figure 16 Axial load envelope in one typical column
Shock and Vibration 13
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus15000 0 15000 30000
Leve
l
minus5
0
5
10
15
20
25
30
35
40
Leve
l
Moment (kNmiddotm)
minus1200 minus800 minus400 0 400 800 1200
Shear (kN)
Option-1Option-2
Option-3Option-4
Option-1Option-2
Option-3Option-4
Figure 17 Moment and shear envelope in one typical column
minus20 minus10 00 10 20
Base
shea
r (kN
)
Top displacement (m)
Option-1Option-2
Option-3Option-4
300E + 04
200E + 04
100E + 04
000E + 00
minus100E + 04
minus200E + 04
minus300E + 04
Figure 18 Base shear versus top displacement relationship in firstmode load pattern
displacement is compared in Figure 18 It can be seen that thiscurve is flag shaped for Option-1 whereas it is bilinear pinch-ing type in Options-2ndash4There is no permanent deformationin controlled structure and flag shaped hysteresis behaviouris observed The same behaviour was observed during testconducted on a large-scale model of a concrete shear wallfrom the core of a high-rise building in the study of Adebar etal [27] The combination of low percentage of vertical rein-forcement and large axial compression force due to gravity
loads (axial force(concrete 28 days cylinder strength times grossarea ofwall)gt 01) caused the flexural cracks to closewhen thelateral load was removed In Options-2ndash4 small permanentdeformation (residual displacement) is observed This isbecause of the plastification of BRBs as well as transfer of themoment demand from shear wall to columns in the form ofaxial push-pull
8 Conclusions
(i) In this study different options of location of BRBsare investigated for a 40-story case study buildingThe locations of BRBs are identified based on theDBE elastic racking shear deformation and shear andbending moment demands in dominant 2nd and 3rdmodes NLRHA is then performed for seven sets ofspectrally matched target time histories and resultsare compared for different options
(ii) In all options shear force demands bending momentat mid height displacement demand racking sheardeformation demand and rotation demand in cou-pling beams are reduced by 10 45 45 45 and40 respectively in comparison to the controlledstructure
(iii) Rotational demand in the core wall at base level isreduced by 99 57 and 93 in Option-2 Option-3 and Option-4 respectively in comparison toOption-1Whereas energy dissipated by the core wallis reduced by around 250 in the corewall in compar-ison to the controlled structure Rotational demandand energy dissipation are measure of damage in thecore wall Thus damage can be significantly reducedby installation of BRBs
14 Shock and Vibration
(iv) All BRBs options are effective for bending momentreduction at mid height displacement and rackingshear deformation demands along the wall heightand rotation demand at the base of the wall and incoupling beams above the mid height of the build-ing However Option-4 in which BRBs are installedbetween peripheral columns and central corewall andcut in shear walls based on the maximum shear forceand bending moment leads to the highest reductionThis is because of the early yielding of the interiorbraces
(v) Thiswork is equally important for academia and prac-tising engineers especially those working in the fieldof performance based design of the high-rise build-ings in the commercial consultancy This will helpthem to locate BRBs at appropriate locations whiledesigning their buildings in an optimal way
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] International Conference of Building Officials Uniform Build-ing Code vol 2 International Conference of Building OfficialsWhittier Calif USA 1997
[2] J Maffei and N Yuen ldquoSeismic performance and designrequirements for high rise buildingsrdquo Structural Magazine pp28ndash32 2007
[3] J P Moehle ldquoPerformance-based seismic design of tall build-ings in the USrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[4] CEN EC8 Design of Structures for Earthquake ResistanceEuropean Committee for Standardization Brussels Belgium2004
[5] NZS 3101 Part 12006 Concrete Structures Standards NewZealand Standards New Zealand Wellington New Zealand2006
[6] T Paulay and M J N Priestley Seismic Design of ReinforcedConcrete and Masonry Buildings Wiley Hoboken NJ USA1992
[7] M Panagiotou J I Restrepo and J P Conte ldquoShake table test ofa 7-story full scale reinforced concrete structural wall buildingslice phase I rectangular wallrdquo Report SSRP 07-07 Departmentof Structural Engineering University of California San DiegoSan Diego Calif USA 2007
[8] Canadian Standard Association CSA Standard A233-04Design of Concrete Structures Canadian Standard AssociationRexdale Canada 2005
[9] R Klemencic J A Fry J D Hooper and B G MorgenldquoPerformance-based design of ductile concrete core wall build-ingsmdashissues to consider before detailed analysisrdquoTheStructuralDesign of Tall and Special Buildings vol 16 no 5 pp 599ndash6142007
[10] R Klemencic ldquoPerformance based seismic designmdashrisingrdquoStructural Magazine 2008 httpwwwstructuremagorgwp-contentuploads201408C-StructuralPractices-Klemencic-June081pdf
[11] A Zekioglu M Willford L Jin and M Melek ldquoCase studyusing the Los Angeles tall buildings structural design councilguidelines 40-storey concrete core wall buildingrdquo StructuralDesign of Tall and Special Buildings vol 16 no 5 pp 583ndash5972007
[12] B R Rad and P Adebar ldquoDynamic shear amplification inhigh-rise concrete walls effect of multiple flexural hinges andshear crackingrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[13] M Panagiotou and J I Restrepo ldquoDual-plastic hinge designconcept for reducing higher-mode effects on high-rise can-tilever wall buildingsrdquo Earthquake Engineering and StructuralDynamics vol 38 no 12 pp 1359ndash1380 2009
[14] M Ahmed and P Warnitchai ldquoReduction of inelastic seismicdemands by inducing plastic hinges at effective locationsrdquoin Proceedings of the 3rd Asian Conference on EarthquakeEngineering (ACEE rsquo10) Bangkok Thailand December 2010
[15] A Munir and P Warnitchai ldquoThe cause of unproportion-ately large higher mode contributions in the inelastic seismicresponses of high-rise core-wall buildingsrdquo Earthquake Engi-neering amp Structural Dynamics vol 41 no 15 pp 2195ndash22142012
[16] A Munir and P Warnitchai ldquoOptimal reduction of inelasticseismic demands in high-rise reinforced concrete core wallbuildings using energy-dissipating devicesrdquo Structural Design ofTall and Special Buildings vol 22 no 7 pp 543ndash568 2013
[17] M C Constantinou and M D Symans ldquoExperimental andanalytical investigation of seismic response of structures withsupplemental fluid viscous dampersrdquo NCEER Reports 92-0032State University of New York at Buffalo Buffalo NY USA 1992
[18] A SWhittaker V V Bertero C LThompson and L J AlonsoldquoSeismic testing of steel plate energy dissipation devicesrdquoEarthquake Spectra vol 7 no 4 pp 563ndash604 1991
[19] G W Housner L A Bergman T K Caughey et al ldquoStruc-tural control past present and futurerdquo Journal of EngineeringMechanics vol 123 no 9 pp 897ndash971 1997
[20] M D Symans F A Charney A S Whittaker et al ldquoEnergydissipation systems for seismic applications current practiceand recent developmentsrdquo Journal of Structural Engineering vol134 no 1 pp 3ndash21 2008
[21] C J Black N Makris and I D Aiken ldquoComponent testingseismic evaluation and characterization of buckling-restrainedbracesrdquo Journal of Structural Engineering vol 130 no 6 pp880ndash894 2004
[22] S Keten A performance based approach for seismic designwith hysteretic dampers [MS thesis] Massachusetts Institute ofTechnology (MIT) 2006 httpdspacemitedubitstreamhan-dle172113459571252112-MITpdfsequence=2
[23] N Anwar J A Sy T H Aung and D Rayamajhi ldquoFirstapplication of buckling restraint brace system in Philippines ina 50-story building with ductile core wall and PT slab systemrdquoin Proceedings of the 9th International Conference on UrbanEarthquake Engineering and the 4th Asia Conference on Earth-quake Engineering Tokyo Institute of Technology Tokyo JapanMarch 2012
[24] Computers and Structures Inc ETABS Extended 3D Analysis ofBuilding Systems Software Nonlinear Version 900 Computersand Structures Inc Berkeley Calif USA 2005
[25] Computers and Structures Perform 3D Nonlinear Analysis andPerformance Assessment for 3D Structures User Guide Version 4Computers and Structures Berkeley Calif USA 2006
Shock and Vibration 15
[26] J W Wallace and J P Moehle ldquoDuctility and detailing require-ments of bearing wall buildingsrdquo Journal of Structural Engineer-ing vol 118 no 6 pp 1625ndash1644 1992
[27] P Adebar A M M Ibrahim and M Bryson ldquoTest of high-risecore wall effective stiffness for seismic analysisrdquo ACI StructuralJournal vol 104 no 5 pp 549ndash559 2007
[28] FEMA ldquoPrestandard and commentary for the seismic rehabil-itation of buildingsrdquo FEMA 356 Federal Emergency Manage-ment Agency Washington DC USA 2000
[29] LATBDSC An Alternative Procedure for Seismic Analysis andDesign of Tall Buildings Located in Los Angeles Region A Con-sensus Document Los Angeles Tall Buildings and StructuralDesign Council 2008
[30] PEERNGAData Base Pacific Earthquake Engineering Research(PEER) University of California Berkeley Calif USA 2005httppeerberkeleyedunga
[31] COSMOS Data Base ldquoConsortium of organization for strong-motion observation systemsrdquo Tech Rep University of Cali-fornia Berkeley Calif USA 1999ndash2007 httpwwwcosmos-eqorgscriptsdefaultplx
[32] K Lilhanand and W S Tseng ldquoDevelopment and applicationof realistic earthquake time histories compatible with multipledamping design spectrardquo in Proceedings of the 9th World Con-ference on Earthquake Engineering Tokyo Japan August 1988
[33] J Hancock J Watson-Lamprey N A Abrahamson et al ldquoAnimproved method of matching response spectra of recordedearthquake ground motion using waveletsrdquo Journal of Earth-quake Engineering vol 10 no 1 pp 67ndash89 2006
[34] J B Mander M J N Priestley and R Park ldquoTheoreticalstress-strain model for confined concreterdquo Journal of StructuralEngineering New York vol 114 no 8 pp 1804ndash1826 1988
[35] CTBUH Seismic Working Group CTBUH Recommendationsfor the Seismic Design of High-Rise Buildings A ConsensusDocument 2008
[36] N Satake K-I Suda T Arakawa A Sasaki and Y TamuraldquoDamping evaluation using full-scale data of buildings inJapanrdquo Journal of Structural Engineering vol 129 no 4 pp 470ndash477 2003
[37] Q Xie ldquoState of the art of buckling-restrained braces in AsiardquoJournal of Constructional Steel Research vol 61 no 6 pp 727ndash748 2005
[38] P Clark K Kasai I Aiken E Ko and I Kimura ldquoDesign proce-dures for buildings incorporating hysteretic energy dissipatingdevicesrdquo in Proceedings of the 68th Annual Convention Struc-tural Engineers Association of California Santa Barbara CalifUSA October 1999
[39] D Vafaei and R Eskandari ldquoSeismic response of mega buck-ling-restrained braces subjected to fling-step and forward-directivity near-fault ground motionsrdquo Structural Design of Talland Special Buildings vol 24 no 9 pp 672ndash686 2015
[40] L Di Sarno and A S Elnashai ldquoBracing systems for seismicretrofitting of steel framesrdquo Journal of Constructional SteelResearch vol 65 no 2 pp 452ndash465 2009
[41] A Dutta and R O Hamburger ldquoCase study of A 40-Storeybuckling-restrained braced frame building located in LosAnge-lesrdquo The Structural Design of Tall and Special Buildings vol 19no 1-2 pp 77ndash93 2010
[42] Rutherford amp Chekene ldquoPerform nonlinear component mod-elling of star seismic powercat BRBsrdquo Report to Star SeismicLLC Star Seismic LLC 2011
[43] P Dusicka A M Itani and I G Buckle ldquoCyclic response ofplate steels under large inelastic strainsrdquo Journal of Construc-tional Steel Research vol 63 no 2 pp 156ndash164 2007
[44] S A Razavi M E Shemshadian S R Mirghaderi and SAhlehagh ldquoSeismic design of buckling restrained braced frameswith reduced core lengthrdquo in Proceedings of the The StructuralEngineers World Congress Cernobbio Italy 2011
[45] S A Razavi S R Mirghaderi A Hosseini and M EShemshadian ldquoReduced length buckling restrained brace usingsteel plates as restraining segmentrdquo in Proceedings of the 15thWorld Conference on Earthquake Engineering Lisboa PurtagalSeptember 2012
[46] M E Shemshadian S A Razavi S R Mirghaderi A Hosseiniand M K Mohammadi ldquoThe advantages of reducing thelength of yielding segment in seismic performance of bucklingrestrained braced framesrdquo inProceedings of the 6th InternationalConference of Seismology and Earthquake Engineering TehranIran 2011
[47] N Ma B Wu J Zhao H Li J Ou andW Yang ldquoFull scale testof all-steel buckling restrained bracesrdquo in Proceedings of the 14thWorld Conference on Earthquake Engineering Beijing ChinaOctober 2008
[48] L Di Sarno and G Manfredi ldquoSeismic retrofitting of existingRC frames with buckling restrained bracesrdquo in Proceedings ofthe Improving the Seismic Performance of Existing Buildingsand Other Structures pp 741ndash752 San Francisco Calif USADecember 2009
[49] S Ahlehagh Improvement of the special concentrically bracedsteel frames behaviour by employing balanced braces [MSthesis] University of Tehran Tehran Iran 2008
[50] R Tremblay P Bolduc R Neville and R DeVall ldquoSeismic test-ing and performance of buckling-restrained bracing systemsrdquoCanadian Journal of Civil Engineering vol 33 no 2 pp 183ndash1982006
Figure 12 MCE inelastic shear and moment demands in different options (a) Shear (b) moment
0 05 1 15 2 25Displacement (m)minus5
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(a)
0 001 002 003 004Racking shear deformation ratio
0
5
10
15
20
25
30
35
40
Leve
l
Option-1Option-2
Option-3Option-4
(b)
Figure 13 MCE inelastic displacement and racking deformation demands in different options (a) Displacement (b) racking sheardeformation angle
along the wall height by 40 40 and 65 in Option-2Option-3 and Option-4 respectively in comparison to thatin 1st option This is significant reduction Racking sheardeformations of 0036 in the controlled structures are reducedto 0023 which is well within the limit of 003 set by [29]LATBSDC 2008 for the MCE level earthquake
Rotational demands in the core wall at the base level aswell as in coupling beams along the height are shown in Fig-ures 14(a) and 14(b) respectivelyThe rotation demand in thewall is calculated by multiplying the average curvature at themid height of the inelastic wall element by height of the wallThe comparison shows that themaximum rotational demand
at the base of the wall is reduced by 99 57 and 93 inOption-2Option-3 andOption-4 respectively in comparison to thatin 1st option This is strong indication that damage at thebase of the wall shall be reduced to half and consequentlyextent of repair shall be small and hence cheap in case ofsevere MCE events such as DBE and MCE level earthquakeThe rotational demands in coupling beams are reduced by52 40 and 35 respectively above the half height level forOption-2 Option-3 and Option-4 respectively in compar-ison to 1st option However rotation demand remained thesame in the lower half portion of the building for all options
Energy dissipated by core wall coupling beams andbuckling restrained braces have been compared in Figures15(a)ndash15(d) respectively for Option-1 Option-2 Option-3 and Option-4 respectively This is energy dissipated inpercentage of the total energy demand in the structure Thetotal energy demand is sum of the kinetic energy elasticstrain energy energy dissipated by elastic modal dampingand energy dissipation by damage in structural elements suchas core wall coupling beams and BRBs About 83 9292 and 90 energy have been dissipated by elastic modaland inelastic damping in Option-1 to Option-4 respectivelyThe energy dissipation by modal elastic damping to the totalenergy demands is 50 37 35 and 33 respectively inOption-1 to Option-4 respectivelyThe energy dissipation bycore wall at the base to the total energy demands is 22 66 and 6 inOption-1 to Option-4 respectivelyThe energydissipation by coupling beams to the total energy demands isapproximately 10 4 5 and 6 in Option-1 to Option-4 respectively The energy dissipation by BRBs to the total
energy demands is 0 45 45 and 45 respectively inOption-1 to Option-4
7 Effects of BRBs on Axial Loads Shearand Moment of Columns and PermanentDeformation due to BRBs Plastification
Effects of BRBs on axial loads of columns and permanentdeformation due to BRBs plastification have been discussedin this section The axial load envelope in a typical columnfor Options-1ndash4 is shown in the Figure 16 The magnitude ofaxial load is same for Options-2ndash4 (with BRBs) and is twicethan that in Option-1 (controlled structure) This is due tothe outrigger effect created by the connection of columnsand core wall through BRBs Some core wall moment hasbeen resisted by the development of axial push-pull in thecolumns Furthermore the shape of the axial load envelopeis smooth in case of Option-1 whereas it is jagged at thelocations of the BRBs forOptions-2ndash4Themoment envelopeand shear envelope for one typical column are shown inFigures 17(a) and 17(b) respectively It shows that momentand shear have been reduced at the ground level in Options-2ndash4 in comparison to Option-1 whereas these remain almostthe same at upper portions The extra moment and shearat the ground level in Options-1ndash4 is due to the transfer ofmoment and shear to the columns when core wall yields
To better understand the permanent deformation in thestructure due to BRBs plastification cyclic pushover analysisin firstmode is performedusing target displacement obtainedfrom NLTHA for all cases The cyclic base shear versus top
12 Shock and Vibration
Option-1
0
20
40
60
80
100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 53478kNmiddotm
(a)
Option-2
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 73328kNmiddotm
(b)
Option-3
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80 90
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 71449kNmiddotm
(c)
Option-4
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 69558kNmiddotm
(d)
Figure 15 Inelastic energy demands in structural components (a) to (d) For Option-1 to Option-4 respectively
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus20000 minus10000 0
Leve
l
Axial load (kN)
Option-1Option-2
Option-3Option-4
Figure 16 Axial load envelope in one typical column
Shock and Vibration 13
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus15000 0 15000 30000
Leve
l
minus5
0
5
10
15
20
25
30
35
40
Leve
l
Moment (kNmiddotm)
minus1200 minus800 minus400 0 400 800 1200
Shear (kN)
Option-1Option-2
Option-3Option-4
Option-1Option-2
Option-3Option-4
Figure 17 Moment and shear envelope in one typical column
minus20 minus10 00 10 20
Base
shea
r (kN
)
Top displacement (m)
Option-1Option-2
Option-3Option-4
300E + 04
200E + 04
100E + 04
000E + 00
minus100E + 04
minus200E + 04
minus300E + 04
Figure 18 Base shear versus top displacement relationship in firstmode load pattern
displacement is compared in Figure 18 It can be seen that thiscurve is flag shaped for Option-1 whereas it is bilinear pinch-ing type in Options-2ndash4There is no permanent deformationin controlled structure and flag shaped hysteresis behaviouris observed The same behaviour was observed during testconducted on a large-scale model of a concrete shear wallfrom the core of a high-rise building in the study of Adebar etal [27] The combination of low percentage of vertical rein-forcement and large axial compression force due to gravity
loads (axial force(concrete 28 days cylinder strength times grossarea ofwall)gt 01) caused the flexural cracks to closewhen thelateral load was removed In Options-2ndash4 small permanentdeformation (residual displacement) is observed This isbecause of the plastification of BRBs as well as transfer of themoment demand from shear wall to columns in the form ofaxial push-pull
8 Conclusions
(i) In this study different options of location of BRBsare investigated for a 40-story case study buildingThe locations of BRBs are identified based on theDBE elastic racking shear deformation and shear andbending moment demands in dominant 2nd and 3rdmodes NLRHA is then performed for seven sets ofspectrally matched target time histories and resultsare compared for different options
(ii) In all options shear force demands bending momentat mid height displacement demand racking sheardeformation demand and rotation demand in cou-pling beams are reduced by 10 45 45 45 and40 respectively in comparison to the controlledstructure
(iii) Rotational demand in the core wall at base level isreduced by 99 57 and 93 in Option-2 Option-3 and Option-4 respectively in comparison toOption-1Whereas energy dissipated by the core wallis reduced by around 250 in the corewall in compar-ison to the controlled structure Rotational demandand energy dissipation are measure of damage in thecore wall Thus damage can be significantly reducedby installation of BRBs
14 Shock and Vibration
(iv) All BRBs options are effective for bending momentreduction at mid height displacement and rackingshear deformation demands along the wall heightand rotation demand at the base of the wall and incoupling beams above the mid height of the build-ing However Option-4 in which BRBs are installedbetween peripheral columns and central corewall andcut in shear walls based on the maximum shear forceand bending moment leads to the highest reductionThis is because of the early yielding of the interiorbraces
(v) Thiswork is equally important for academia and prac-tising engineers especially those working in the fieldof performance based design of the high-rise build-ings in the commercial consultancy This will helpthem to locate BRBs at appropriate locations whiledesigning their buildings in an optimal way
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] International Conference of Building Officials Uniform Build-ing Code vol 2 International Conference of Building OfficialsWhittier Calif USA 1997
[2] J Maffei and N Yuen ldquoSeismic performance and designrequirements for high rise buildingsrdquo Structural Magazine pp28ndash32 2007
[3] J P Moehle ldquoPerformance-based seismic design of tall build-ings in the USrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[4] CEN EC8 Design of Structures for Earthquake ResistanceEuropean Committee for Standardization Brussels Belgium2004
[5] NZS 3101 Part 12006 Concrete Structures Standards NewZealand Standards New Zealand Wellington New Zealand2006
[6] T Paulay and M J N Priestley Seismic Design of ReinforcedConcrete and Masonry Buildings Wiley Hoboken NJ USA1992
[7] M Panagiotou J I Restrepo and J P Conte ldquoShake table test ofa 7-story full scale reinforced concrete structural wall buildingslice phase I rectangular wallrdquo Report SSRP 07-07 Departmentof Structural Engineering University of California San DiegoSan Diego Calif USA 2007
[8] Canadian Standard Association CSA Standard A233-04Design of Concrete Structures Canadian Standard AssociationRexdale Canada 2005
[9] R Klemencic J A Fry J D Hooper and B G MorgenldquoPerformance-based design of ductile concrete core wall build-ingsmdashissues to consider before detailed analysisrdquoTheStructuralDesign of Tall and Special Buildings vol 16 no 5 pp 599ndash6142007
[10] R Klemencic ldquoPerformance based seismic designmdashrisingrdquoStructural Magazine 2008 httpwwwstructuremagorgwp-contentuploads201408C-StructuralPractices-Klemencic-June081pdf
[11] A Zekioglu M Willford L Jin and M Melek ldquoCase studyusing the Los Angeles tall buildings structural design councilguidelines 40-storey concrete core wall buildingrdquo StructuralDesign of Tall and Special Buildings vol 16 no 5 pp 583ndash5972007
[12] B R Rad and P Adebar ldquoDynamic shear amplification inhigh-rise concrete walls effect of multiple flexural hinges andshear crackingrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[13] M Panagiotou and J I Restrepo ldquoDual-plastic hinge designconcept for reducing higher-mode effects on high-rise can-tilever wall buildingsrdquo Earthquake Engineering and StructuralDynamics vol 38 no 12 pp 1359ndash1380 2009
[14] M Ahmed and P Warnitchai ldquoReduction of inelastic seismicdemands by inducing plastic hinges at effective locationsrdquoin Proceedings of the 3rd Asian Conference on EarthquakeEngineering (ACEE rsquo10) Bangkok Thailand December 2010
[15] A Munir and P Warnitchai ldquoThe cause of unproportion-ately large higher mode contributions in the inelastic seismicresponses of high-rise core-wall buildingsrdquo Earthquake Engi-neering amp Structural Dynamics vol 41 no 15 pp 2195ndash22142012
[16] A Munir and P Warnitchai ldquoOptimal reduction of inelasticseismic demands in high-rise reinforced concrete core wallbuildings using energy-dissipating devicesrdquo Structural Design ofTall and Special Buildings vol 22 no 7 pp 543ndash568 2013
[17] M C Constantinou and M D Symans ldquoExperimental andanalytical investigation of seismic response of structures withsupplemental fluid viscous dampersrdquo NCEER Reports 92-0032State University of New York at Buffalo Buffalo NY USA 1992
[18] A SWhittaker V V Bertero C LThompson and L J AlonsoldquoSeismic testing of steel plate energy dissipation devicesrdquoEarthquake Spectra vol 7 no 4 pp 563ndash604 1991
[19] G W Housner L A Bergman T K Caughey et al ldquoStruc-tural control past present and futurerdquo Journal of EngineeringMechanics vol 123 no 9 pp 897ndash971 1997
[20] M D Symans F A Charney A S Whittaker et al ldquoEnergydissipation systems for seismic applications current practiceand recent developmentsrdquo Journal of Structural Engineering vol134 no 1 pp 3ndash21 2008
[21] C J Black N Makris and I D Aiken ldquoComponent testingseismic evaluation and characterization of buckling-restrainedbracesrdquo Journal of Structural Engineering vol 130 no 6 pp880ndash894 2004
[22] S Keten A performance based approach for seismic designwith hysteretic dampers [MS thesis] Massachusetts Institute ofTechnology (MIT) 2006 httpdspacemitedubitstreamhan-dle172113459571252112-MITpdfsequence=2
[23] N Anwar J A Sy T H Aung and D Rayamajhi ldquoFirstapplication of buckling restraint brace system in Philippines ina 50-story building with ductile core wall and PT slab systemrdquoin Proceedings of the 9th International Conference on UrbanEarthquake Engineering and the 4th Asia Conference on Earth-quake Engineering Tokyo Institute of Technology Tokyo JapanMarch 2012
[24] Computers and Structures Inc ETABS Extended 3D Analysis ofBuilding Systems Software Nonlinear Version 900 Computersand Structures Inc Berkeley Calif USA 2005
[25] Computers and Structures Perform 3D Nonlinear Analysis andPerformance Assessment for 3D Structures User Guide Version 4Computers and Structures Berkeley Calif USA 2006
Shock and Vibration 15
[26] J W Wallace and J P Moehle ldquoDuctility and detailing require-ments of bearing wall buildingsrdquo Journal of Structural Engineer-ing vol 118 no 6 pp 1625ndash1644 1992
[27] P Adebar A M M Ibrahim and M Bryson ldquoTest of high-risecore wall effective stiffness for seismic analysisrdquo ACI StructuralJournal vol 104 no 5 pp 549ndash559 2007
[28] FEMA ldquoPrestandard and commentary for the seismic rehabil-itation of buildingsrdquo FEMA 356 Federal Emergency Manage-ment Agency Washington DC USA 2000
[29] LATBDSC An Alternative Procedure for Seismic Analysis andDesign of Tall Buildings Located in Los Angeles Region A Con-sensus Document Los Angeles Tall Buildings and StructuralDesign Council 2008
[30] PEERNGAData Base Pacific Earthquake Engineering Research(PEER) University of California Berkeley Calif USA 2005httppeerberkeleyedunga
[31] COSMOS Data Base ldquoConsortium of organization for strong-motion observation systemsrdquo Tech Rep University of Cali-fornia Berkeley Calif USA 1999ndash2007 httpwwwcosmos-eqorgscriptsdefaultplx
[32] K Lilhanand and W S Tseng ldquoDevelopment and applicationof realistic earthquake time histories compatible with multipledamping design spectrardquo in Proceedings of the 9th World Con-ference on Earthquake Engineering Tokyo Japan August 1988
[33] J Hancock J Watson-Lamprey N A Abrahamson et al ldquoAnimproved method of matching response spectra of recordedearthquake ground motion using waveletsrdquo Journal of Earth-quake Engineering vol 10 no 1 pp 67ndash89 2006
[34] J B Mander M J N Priestley and R Park ldquoTheoreticalstress-strain model for confined concreterdquo Journal of StructuralEngineering New York vol 114 no 8 pp 1804ndash1826 1988
[35] CTBUH Seismic Working Group CTBUH Recommendationsfor the Seismic Design of High-Rise Buildings A ConsensusDocument 2008
[36] N Satake K-I Suda T Arakawa A Sasaki and Y TamuraldquoDamping evaluation using full-scale data of buildings inJapanrdquo Journal of Structural Engineering vol 129 no 4 pp 470ndash477 2003
[37] Q Xie ldquoState of the art of buckling-restrained braces in AsiardquoJournal of Constructional Steel Research vol 61 no 6 pp 727ndash748 2005
[38] P Clark K Kasai I Aiken E Ko and I Kimura ldquoDesign proce-dures for buildings incorporating hysteretic energy dissipatingdevicesrdquo in Proceedings of the 68th Annual Convention Struc-tural Engineers Association of California Santa Barbara CalifUSA October 1999
[39] D Vafaei and R Eskandari ldquoSeismic response of mega buck-ling-restrained braces subjected to fling-step and forward-directivity near-fault ground motionsrdquo Structural Design of Talland Special Buildings vol 24 no 9 pp 672ndash686 2015
[40] L Di Sarno and A S Elnashai ldquoBracing systems for seismicretrofitting of steel framesrdquo Journal of Constructional SteelResearch vol 65 no 2 pp 452ndash465 2009
[41] A Dutta and R O Hamburger ldquoCase study of A 40-Storeybuckling-restrained braced frame building located in LosAnge-lesrdquo The Structural Design of Tall and Special Buildings vol 19no 1-2 pp 77ndash93 2010
[42] Rutherford amp Chekene ldquoPerform nonlinear component mod-elling of star seismic powercat BRBsrdquo Report to Star SeismicLLC Star Seismic LLC 2011
[43] P Dusicka A M Itani and I G Buckle ldquoCyclic response ofplate steels under large inelastic strainsrdquo Journal of Construc-tional Steel Research vol 63 no 2 pp 156ndash164 2007
[44] S A Razavi M E Shemshadian S R Mirghaderi and SAhlehagh ldquoSeismic design of buckling restrained braced frameswith reduced core lengthrdquo in Proceedings of the The StructuralEngineers World Congress Cernobbio Italy 2011
[45] S A Razavi S R Mirghaderi A Hosseini and M EShemshadian ldquoReduced length buckling restrained brace usingsteel plates as restraining segmentrdquo in Proceedings of the 15thWorld Conference on Earthquake Engineering Lisboa PurtagalSeptember 2012
[46] M E Shemshadian S A Razavi S R Mirghaderi A Hosseiniand M K Mohammadi ldquoThe advantages of reducing thelength of yielding segment in seismic performance of bucklingrestrained braced framesrdquo inProceedings of the 6th InternationalConference of Seismology and Earthquake Engineering TehranIran 2011
[47] N Ma B Wu J Zhao H Li J Ou andW Yang ldquoFull scale testof all-steel buckling restrained bracesrdquo in Proceedings of the 14thWorld Conference on Earthquake Engineering Beijing ChinaOctober 2008
[48] L Di Sarno and G Manfredi ldquoSeismic retrofitting of existingRC frames with buckling restrained bracesrdquo in Proceedings ofthe Improving the Seismic Performance of Existing Buildingsand Other Structures pp 741ndash752 San Francisco Calif USADecember 2009
[49] S Ahlehagh Improvement of the special concentrically bracedsteel frames behaviour by employing balanced braces [MSthesis] University of Tehran Tehran Iran 2008
[50] R Tremblay P Bolduc R Neville and R DeVall ldquoSeismic test-ing and performance of buckling-restrained bracing systemsrdquoCanadian Journal of Civil Engineering vol 33 no 2 pp 183ndash1982006
at the base of the wall is reduced by 99 57 and 93 inOption-2Option-3 andOption-4 respectively in comparison to thatin 1st option This is strong indication that damage at thebase of the wall shall be reduced to half and consequentlyextent of repair shall be small and hence cheap in case ofsevere MCE events such as DBE and MCE level earthquakeThe rotational demands in coupling beams are reduced by52 40 and 35 respectively above the half height level forOption-2 Option-3 and Option-4 respectively in compar-ison to 1st option However rotation demand remained thesame in the lower half portion of the building for all options
Energy dissipated by core wall coupling beams andbuckling restrained braces have been compared in Figures15(a)ndash15(d) respectively for Option-1 Option-2 Option-3 and Option-4 respectively This is energy dissipated inpercentage of the total energy demand in the structure Thetotal energy demand is sum of the kinetic energy elasticstrain energy energy dissipated by elastic modal dampingand energy dissipation by damage in structural elements suchas core wall coupling beams and BRBs About 83 9292 and 90 energy have been dissipated by elastic modaland inelastic damping in Option-1 to Option-4 respectivelyThe energy dissipation by modal elastic damping to the totalenergy demands is 50 37 35 and 33 respectively inOption-1 to Option-4 respectivelyThe energy dissipation bycore wall at the base to the total energy demands is 22 66 and 6 inOption-1 to Option-4 respectivelyThe energydissipation by coupling beams to the total energy demands isapproximately 10 4 5 and 6 in Option-1 to Option-4 respectively The energy dissipation by BRBs to the total
energy demands is 0 45 45 and 45 respectively inOption-1 to Option-4
7 Effects of BRBs on Axial Loads Shearand Moment of Columns and PermanentDeformation due to BRBs Plastification
Effects of BRBs on axial loads of columns and permanentdeformation due to BRBs plastification have been discussedin this section The axial load envelope in a typical columnfor Options-1ndash4 is shown in the Figure 16 The magnitude ofaxial load is same for Options-2ndash4 (with BRBs) and is twicethan that in Option-1 (controlled structure) This is due tothe outrigger effect created by the connection of columnsand core wall through BRBs Some core wall moment hasbeen resisted by the development of axial push-pull in thecolumns Furthermore the shape of the axial load envelopeis smooth in case of Option-1 whereas it is jagged at thelocations of the BRBs forOptions-2ndash4Themoment envelopeand shear envelope for one typical column are shown inFigures 17(a) and 17(b) respectively It shows that momentand shear have been reduced at the ground level in Options-2ndash4 in comparison to Option-1 whereas these remain almostthe same at upper portions The extra moment and shearat the ground level in Options-1ndash4 is due to the transfer ofmoment and shear to the columns when core wall yields
To better understand the permanent deformation in thestructure due to BRBs plastification cyclic pushover analysisin firstmode is performedusing target displacement obtainedfrom NLTHA for all cases The cyclic base shear versus top
12 Shock and Vibration
Option-1
0
20
40
60
80
100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 53478kNmiddotm
(a)
Option-2
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 73328kNmiddotm
(b)
Option-3
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80 90
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 71449kNmiddotm
(c)
Option-4
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 69558kNmiddotm
(d)
Figure 15 Inelastic energy demands in structural components (a) to (d) For Option-1 to Option-4 respectively
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus20000 minus10000 0
Leve
l
Axial load (kN)
Option-1Option-2
Option-3Option-4
Figure 16 Axial load envelope in one typical column
Shock and Vibration 13
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus15000 0 15000 30000
Leve
l
minus5
0
5
10
15
20
25
30
35
40
Leve
l
Moment (kNmiddotm)
minus1200 minus800 minus400 0 400 800 1200
Shear (kN)
Option-1Option-2
Option-3Option-4
Option-1Option-2
Option-3Option-4
Figure 17 Moment and shear envelope in one typical column
minus20 minus10 00 10 20
Base
shea
r (kN
)
Top displacement (m)
Option-1Option-2
Option-3Option-4
300E + 04
200E + 04
100E + 04
000E + 00
minus100E + 04
minus200E + 04
minus300E + 04
Figure 18 Base shear versus top displacement relationship in firstmode load pattern
displacement is compared in Figure 18 It can be seen that thiscurve is flag shaped for Option-1 whereas it is bilinear pinch-ing type in Options-2ndash4There is no permanent deformationin controlled structure and flag shaped hysteresis behaviouris observed The same behaviour was observed during testconducted on a large-scale model of a concrete shear wallfrom the core of a high-rise building in the study of Adebar etal [27] The combination of low percentage of vertical rein-forcement and large axial compression force due to gravity
loads (axial force(concrete 28 days cylinder strength times grossarea ofwall)gt 01) caused the flexural cracks to closewhen thelateral load was removed In Options-2ndash4 small permanentdeformation (residual displacement) is observed This isbecause of the plastification of BRBs as well as transfer of themoment demand from shear wall to columns in the form ofaxial push-pull
8 Conclusions
(i) In this study different options of location of BRBsare investigated for a 40-story case study buildingThe locations of BRBs are identified based on theDBE elastic racking shear deformation and shear andbending moment demands in dominant 2nd and 3rdmodes NLRHA is then performed for seven sets ofspectrally matched target time histories and resultsare compared for different options
(ii) In all options shear force demands bending momentat mid height displacement demand racking sheardeformation demand and rotation demand in cou-pling beams are reduced by 10 45 45 45 and40 respectively in comparison to the controlledstructure
(iii) Rotational demand in the core wall at base level isreduced by 99 57 and 93 in Option-2 Option-3 and Option-4 respectively in comparison toOption-1Whereas energy dissipated by the core wallis reduced by around 250 in the corewall in compar-ison to the controlled structure Rotational demandand energy dissipation are measure of damage in thecore wall Thus damage can be significantly reducedby installation of BRBs
14 Shock and Vibration
(iv) All BRBs options are effective for bending momentreduction at mid height displacement and rackingshear deformation demands along the wall heightand rotation demand at the base of the wall and incoupling beams above the mid height of the build-ing However Option-4 in which BRBs are installedbetween peripheral columns and central corewall andcut in shear walls based on the maximum shear forceand bending moment leads to the highest reductionThis is because of the early yielding of the interiorbraces
(v) Thiswork is equally important for academia and prac-tising engineers especially those working in the fieldof performance based design of the high-rise build-ings in the commercial consultancy This will helpthem to locate BRBs at appropriate locations whiledesigning their buildings in an optimal way
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] International Conference of Building Officials Uniform Build-ing Code vol 2 International Conference of Building OfficialsWhittier Calif USA 1997
[2] J Maffei and N Yuen ldquoSeismic performance and designrequirements for high rise buildingsrdquo Structural Magazine pp28ndash32 2007
[3] J P Moehle ldquoPerformance-based seismic design of tall build-ings in the USrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[4] CEN EC8 Design of Structures for Earthquake ResistanceEuropean Committee for Standardization Brussels Belgium2004
[5] NZS 3101 Part 12006 Concrete Structures Standards NewZealand Standards New Zealand Wellington New Zealand2006
[6] T Paulay and M J N Priestley Seismic Design of ReinforcedConcrete and Masonry Buildings Wiley Hoboken NJ USA1992
[7] M Panagiotou J I Restrepo and J P Conte ldquoShake table test ofa 7-story full scale reinforced concrete structural wall buildingslice phase I rectangular wallrdquo Report SSRP 07-07 Departmentof Structural Engineering University of California San DiegoSan Diego Calif USA 2007
[8] Canadian Standard Association CSA Standard A233-04Design of Concrete Structures Canadian Standard AssociationRexdale Canada 2005
[9] R Klemencic J A Fry J D Hooper and B G MorgenldquoPerformance-based design of ductile concrete core wall build-ingsmdashissues to consider before detailed analysisrdquoTheStructuralDesign of Tall and Special Buildings vol 16 no 5 pp 599ndash6142007
[10] R Klemencic ldquoPerformance based seismic designmdashrisingrdquoStructural Magazine 2008 httpwwwstructuremagorgwp-contentuploads201408C-StructuralPractices-Klemencic-June081pdf
[11] A Zekioglu M Willford L Jin and M Melek ldquoCase studyusing the Los Angeles tall buildings structural design councilguidelines 40-storey concrete core wall buildingrdquo StructuralDesign of Tall and Special Buildings vol 16 no 5 pp 583ndash5972007
[12] B R Rad and P Adebar ldquoDynamic shear amplification inhigh-rise concrete walls effect of multiple flexural hinges andshear crackingrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[13] M Panagiotou and J I Restrepo ldquoDual-plastic hinge designconcept for reducing higher-mode effects on high-rise can-tilever wall buildingsrdquo Earthquake Engineering and StructuralDynamics vol 38 no 12 pp 1359ndash1380 2009
[14] M Ahmed and P Warnitchai ldquoReduction of inelastic seismicdemands by inducing plastic hinges at effective locationsrdquoin Proceedings of the 3rd Asian Conference on EarthquakeEngineering (ACEE rsquo10) Bangkok Thailand December 2010
[15] A Munir and P Warnitchai ldquoThe cause of unproportion-ately large higher mode contributions in the inelastic seismicresponses of high-rise core-wall buildingsrdquo Earthquake Engi-neering amp Structural Dynamics vol 41 no 15 pp 2195ndash22142012
[16] A Munir and P Warnitchai ldquoOptimal reduction of inelasticseismic demands in high-rise reinforced concrete core wallbuildings using energy-dissipating devicesrdquo Structural Design ofTall and Special Buildings vol 22 no 7 pp 543ndash568 2013
[17] M C Constantinou and M D Symans ldquoExperimental andanalytical investigation of seismic response of structures withsupplemental fluid viscous dampersrdquo NCEER Reports 92-0032State University of New York at Buffalo Buffalo NY USA 1992
[18] A SWhittaker V V Bertero C LThompson and L J AlonsoldquoSeismic testing of steel plate energy dissipation devicesrdquoEarthquake Spectra vol 7 no 4 pp 563ndash604 1991
[19] G W Housner L A Bergman T K Caughey et al ldquoStruc-tural control past present and futurerdquo Journal of EngineeringMechanics vol 123 no 9 pp 897ndash971 1997
[20] M D Symans F A Charney A S Whittaker et al ldquoEnergydissipation systems for seismic applications current practiceand recent developmentsrdquo Journal of Structural Engineering vol134 no 1 pp 3ndash21 2008
[21] C J Black N Makris and I D Aiken ldquoComponent testingseismic evaluation and characterization of buckling-restrainedbracesrdquo Journal of Structural Engineering vol 130 no 6 pp880ndash894 2004
[22] S Keten A performance based approach for seismic designwith hysteretic dampers [MS thesis] Massachusetts Institute ofTechnology (MIT) 2006 httpdspacemitedubitstreamhan-dle172113459571252112-MITpdfsequence=2
[23] N Anwar J A Sy T H Aung and D Rayamajhi ldquoFirstapplication of buckling restraint brace system in Philippines ina 50-story building with ductile core wall and PT slab systemrdquoin Proceedings of the 9th International Conference on UrbanEarthquake Engineering and the 4th Asia Conference on Earth-quake Engineering Tokyo Institute of Technology Tokyo JapanMarch 2012
[24] Computers and Structures Inc ETABS Extended 3D Analysis ofBuilding Systems Software Nonlinear Version 900 Computersand Structures Inc Berkeley Calif USA 2005
[25] Computers and Structures Perform 3D Nonlinear Analysis andPerformance Assessment for 3D Structures User Guide Version 4Computers and Structures Berkeley Calif USA 2006
Shock and Vibration 15
[26] J W Wallace and J P Moehle ldquoDuctility and detailing require-ments of bearing wall buildingsrdquo Journal of Structural Engineer-ing vol 118 no 6 pp 1625ndash1644 1992
[27] P Adebar A M M Ibrahim and M Bryson ldquoTest of high-risecore wall effective stiffness for seismic analysisrdquo ACI StructuralJournal vol 104 no 5 pp 549ndash559 2007
[28] FEMA ldquoPrestandard and commentary for the seismic rehabil-itation of buildingsrdquo FEMA 356 Federal Emergency Manage-ment Agency Washington DC USA 2000
[29] LATBDSC An Alternative Procedure for Seismic Analysis andDesign of Tall Buildings Located in Los Angeles Region A Con-sensus Document Los Angeles Tall Buildings and StructuralDesign Council 2008
[30] PEERNGAData Base Pacific Earthquake Engineering Research(PEER) University of California Berkeley Calif USA 2005httppeerberkeleyedunga
[31] COSMOS Data Base ldquoConsortium of organization for strong-motion observation systemsrdquo Tech Rep University of Cali-fornia Berkeley Calif USA 1999ndash2007 httpwwwcosmos-eqorgscriptsdefaultplx
[32] K Lilhanand and W S Tseng ldquoDevelopment and applicationof realistic earthquake time histories compatible with multipledamping design spectrardquo in Proceedings of the 9th World Con-ference on Earthquake Engineering Tokyo Japan August 1988
[33] J Hancock J Watson-Lamprey N A Abrahamson et al ldquoAnimproved method of matching response spectra of recordedearthquake ground motion using waveletsrdquo Journal of Earth-quake Engineering vol 10 no 1 pp 67ndash89 2006
[34] J B Mander M J N Priestley and R Park ldquoTheoreticalstress-strain model for confined concreterdquo Journal of StructuralEngineering New York vol 114 no 8 pp 1804ndash1826 1988
[35] CTBUH Seismic Working Group CTBUH Recommendationsfor the Seismic Design of High-Rise Buildings A ConsensusDocument 2008
[36] N Satake K-I Suda T Arakawa A Sasaki and Y TamuraldquoDamping evaluation using full-scale data of buildings inJapanrdquo Journal of Structural Engineering vol 129 no 4 pp 470ndash477 2003
[37] Q Xie ldquoState of the art of buckling-restrained braces in AsiardquoJournal of Constructional Steel Research vol 61 no 6 pp 727ndash748 2005
[38] P Clark K Kasai I Aiken E Ko and I Kimura ldquoDesign proce-dures for buildings incorporating hysteretic energy dissipatingdevicesrdquo in Proceedings of the 68th Annual Convention Struc-tural Engineers Association of California Santa Barbara CalifUSA October 1999
[39] D Vafaei and R Eskandari ldquoSeismic response of mega buck-ling-restrained braces subjected to fling-step and forward-directivity near-fault ground motionsrdquo Structural Design of Talland Special Buildings vol 24 no 9 pp 672ndash686 2015
[40] L Di Sarno and A S Elnashai ldquoBracing systems for seismicretrofitting of steel framesrdquo Journal of Constructional SteelResearch vol 65 no 2 pp 452ndash465 2009
[41] A Dutta and R O Hamburger ldquoCase study of A 40-Storeybuckling-restrained braced frame building located in LosAnge-lesrdquo The Structural Design of Tall and Special Buildings vol 19no 1-2 pp 77ndash93 2010
[42] Rutherford amp Chekene ldquoPerform nonlinear component mod-elling of star seismic powercat BRBsrdquo Report to Star SeismicLLC Star Seismic LLC 2011
[43] P Dusicka A M Itani and I G Buckle ldquoCyclic response ofplate steels under large inelastic strainsrdquo Journal of Construc-tional Steel Research vol 63 no 2 pp 156ndash164 2007
[44] S A Razavi M E Shemshadian S R Mirghaderi and SAhlehagh ldquoSeismic design of buckling restrained braced frameswith reduced core lengthrdquo in Proceedings of the The StructuralEngineers World Congress Cernobbio Italy 2011
[45] S A Razavi S R Mirghaderi A Hosseini and M EShemshadian ldquoReduced length buckling restrained brace usingsteel plates as restraining segmentrdquo in Proceedings of the 15thWorld Conference on Earthquake Engineering Lisboa PurtagalSeptember 2012
[46] M E Shemshadian S A Razavi S R Mirghaderi A Hosseiniand M K Mohammadi ldquoThe advantages of reducing thelength of yielding segment in seismic performance of bucklingrestrained braced framesrdquo inProceedings of the 6th InternationalConference of Seismology and Earthquake Engineering TehranIran 2011
[47] N Ma B Wu J Zhao H Li J Ou andW Yang ldquoFull scale testof all-steel buckling restrained bracesrdquo in Proceedings of the 14thWorld Conference on Earthquake Engineering Beijing ChinaOctober 2008
[48] L Di Sarno and G Manfredi ldquoSeismic retrofitting of existingRC frames with buckling restrained bracesrdquo in Proceedings ofthe Improving the Seismic Performance of Existing Buildingsand Other Structures pp 741ndash752 San Francisco Calif USADecember 2009
[49] S Ahlehagh Improvement of the special concentrically bracedsteel frames behaviour by employing balanced braces [MSthesis] University of Tehran Tehran Iran 2008
[50] R Tremblay P Bolduc R Neville and R DeVall ldquoSeismic test-ing and performance of buckling-restrained bracing systemsrdquoCanadian Journal of Civil Engineering vol 33 no 2 pp 183ndash1982006
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 53478kNmiddotm
(a)
Option-2
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 73328kNmiddotm
(b)
Option-3
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80 90
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 71449kNmiddotm
(c)
Option-4
0
20
40
60
80100
Ener
gy d
issip
ated
( ag
e of t
otal
ener
gy)
0 10 20 30 40 50 60 70 80 90Time
Dissipated energy by elastic viscous dampingDissipated inelastic energy by coupling beamsDissipated inelastic energy by shear wallsDissipated inelastic energy by BRBs
Total energy = 69558kNmiddotm
(d)
Figure 15 Inelastic energy demands in structural components (a) to (d) For Option-1 to Option-4 respectively
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus20000 minus10000 0
Leve
l
Axial load (kN)
Option-1Option-2
Option-3Option-4
Figure 16 Axial load envelope in one typical column
Shock and Vibration 13
minus5
0
5
10
15
20
25
30
35
40
minus30000 minus15000 0 15000 30000
Leve
l
minus5
0
5
10
15
20
25
30
35
40
Leve
l
Moment (kNmiddotm)
minus1200 minus800 minus400 0 400 800 1200
Shear (kN)
Option-1Option-2
Option-3Option-4
Option-1Option-2
Option-3Option-4
Figure 17 Moment and shear envelope in one typical column
minus20 minus10 00 10 20
Base
shea
r (kN
)
Top displacement (m)
Option-1Option-2
Option-3Option-4
300E + 04
200E + 04
100E + 04
000E + 00
minus100E + 04
minus200E + 04
minus300E + 04
Figure 18 Base shear versus top displacement relationship in firstmode load pattern
displacement is compared in Figure 18 It can be seen that thiscurve is flag shaped for Option-1 whereas it is bilinear pinch-ing type in Options-2ndash4There is no permanent deformationin controlled structure and flag shaped hysteresis behaviouris observed The same behaviour was observed during testconducted on a large-scale model of a concrete shear wallfrom the core of a high-rise building in the study of Adebar etal [27] The combination of low percentage of vertical rein-forcement and large axial compression force due to gravity
loads (axial force(concrete 28 days cylinder strength times grossarea ofwall)gt 01) caused the flexural cracks to closewhen thelateral load was removed In Options-2ndash4 small permanentdeformation (residual displacement) is observed This isbecause of the plastification of BRBs as well as transfer of themoment demand from shear wall to columns in the form ofaxial push-pull
8 Conclusions
(i) In this study different options of location of BRBsare investigated for a 40-story case study buildingThe locations of BRBs are identified based on theDBE elastic racking shear deformation and shear andbending moment demands in dominant 2nd and 3rdmodes NLRHA is then performed for seven sets ofspectrally matched target time histories and resultsare compared for different options
(ii) In all options shear force demands bending momentat mid height displacement demand racking sheardeformation demand and rotation demand in cou-pling beams are reduced by 10 45 45 45 and40 respectively in comparison to the controlledstructure
(iii) Rotational demand in the core wall at base level isreduced by 99 57 and 93 in Option-2 Option-3 and Option-4 respectively in comparison toOption-1Whereas energy dissipated by the core wallis reduced by around 250 in the corewall in compar-ison to the controlled structure Rotational demandand energy dissipation are measure of damage in thecore wall Thus damage can be significantly reducedby installation of BRBs
14 Shock and Vibration
(iv) All BRBs options are effective for bending momentreduction at mid height displacement and rackingshear deformation demands along the wall heightand rotation demand at the base of the wall and incoupling beams above the mid height of the build-ing However Option-4 in which BRBs are installedbetween peripheral columns and central corewall andcut in shear walls based on the maximum shear forceand bending moment leads to the highest reductionThis is because of the early yielding of the interiorbraces
(v) Thiswork is equally important for academia and prac-tising engineers especially those working in the fieldof performance based design of the high-rise build-ings in the commercial consultancy This will helpthem to locate BRBs at appropriate locations whiledesigning their buildings in an optimal way
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] International Conference of Building Officials Uniform Build-ing Code vol 2 International Conference of Building OfficialsWhittier Calif USA 1997
[2] J Maffei and N Yuen ldquoSeismic performance and designrequirements for high rise buildingsrdquo Structural Magazine pp28ndash32 2007
[3] J P Moehle ldquoPerformance-based seismic design of tall build-ings in the USrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[4] CEN EC8 Design of Structures for Earthquake ResistanceEuropean Committee for Standardization Brussels Belgium2004
[5] NZS 3101 Part 12006 Concrete Structures Standards NewZealand Standards New Zealand Wellington New Zealand2006
[6] T Paulay and M J N Priestley Seismic Design of ReinforcedConcrete and Masonry Buildings Wiley Hoboken NJ USA1992
[7] M Panagiotou J I Restrepo and J P Conte ldquoShake table test ofa 7-story full scale reinforced concrete structural wall buildingslice phase I rectangular wallrdquo Report SSRP 07-07 Departmentof Structural Engineering University of California San DiegoSan Diego Calif USA 2007
[8] Canadian Standard Association CSA Standard A233-04Design of Concrete Structures Canadian Standard AssociationRexdale Canada 2005
[9] R Klemencic J A Fry J D Hooper and B G MorgenldquoPerformance-based design of ductile concrete core wall build-ingsmdashissues to consider before detailed analysisrdquoTheStructuralDesign of Tall and Special Buildings vol 16 no 5 pp 599ndash6142007
[10] R Klemencic ldquoPerformance based seismic designmdashrisingrdquoStructural Magazine 2008 httpwwwstructuremagorgwp-contentuploads201408C-StructuralPractices-Klemencic-June081pdf
[11] A Zekioglu M Willford L Jin and M Melek ldquoCase studyusing the Los Angeles tall buildings structural design councilguidelines 40-storey concrete core wall buildingrdquo StructuralDesign of Tall and Special Buildings vol 16 no 5 pp 583ndash5972007
[12] B R Rad and P Adebar ldquoDynamic shear amplification inhigh-rise concrete walls effect of multiple flexural hinges andshear crackingrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[13] M Panagiotou and J I Restrepo ldquoDual-plastic hinge designconcept for reducing higher-mode effects on high-rise can-tilever wall buildingsrdquo Earthquake Engineering and StructuralDynamics vol 38 no 12 pp 1359ndash1380 2009
[14] M Ahmed and P Warnitchai ldquoReduction of inelastic seismicdemands by inducing plastic hinges at effective locationsrdquoin Proceedings of the 3rd Asian Conference on EarthquakeEngineering (ACEE rsquo10) Bangkok Thailand December 2010
[15] A Munir and P Warnitchai ldquoThe cause of unproportion-ately large higher mode contributions in the inelastic seismicresponses of high-rise core-wall buildingsrdquo Earthquake Engi-neering amp Structural Dynamics vol 41 no 15 pp 2195ndash22142012
[16] A Munir and P Warnitchai ldquoOptimal reduction of inelasticseismic demands in high-rise reinforced concrete core wallbuildings using energy-dissipating devicesrdquo Structural Design ofTall and Special Buildings vol 22 no 7 pp 543ndash568 2013
[17] M C Constantinou and M D Symans ldquoExperimental andanalytical investigation of seismic response of structures withsupplemental fluid viscous dampersrdquo NCEER Reports 92-0032State University of New York at Buffalo Buffalo NY USA 1992
[18] A SWhittaker V V Bertero C LThompson and L J AlonsoldquoSeismic testing of steel plate energy dissipation devicesrdquoEarthquake Spectra vol 7 no 4 pp 563ndash604 1991
[19] G W Housner L A Bergman T K Caughey et al ldquoStruc-tural control past present and futurerdquo Journal of EngineeringMechanics vol 123 no 9 pp 897ndash971 1997
[20] M D Symans F A Charney A S Whittaker et al ldquoEnergydissipation systems for seismic applications current practiceand recent developmentsrdquo Journal of Structural Engineering vol134 no 1 pp 3ndash21 2008
[21] C J Black N Makris and I D Aiken ldquoComponent testingseismic evaluation and characterization of buckling-restrainedbracesrdquo Journal of Structural Engineering vol 130 no 6 pp880ndash894 2004
[22] S Keten A performance based approach for seismic designwith hysteretic dampers [MS thesis] Massachusetts Institute ofTechnology (MIT) 2006 httpdspacemitedubitstreamhan-dle172113459571252112-MITpdfsequence=2
[23] N Anwar J A Sy T H Aung and D Rayamajhi ldquoFirstapplication of buckling restraint brace system in Philippines ina 50-story building with ductile core wall and PT slab systemrdquoin Proceedings of the 9th International Conference on UrbanEarthquake Engineering and the 4th Asia Conference on Earth-quake Engineering Tokyo Institute of Technology Tokyo JapanMarch 2012
[24] Computers and Structures Inc ETABS Extended 3D Analysis ofBuilding Systems Software Nonlinear Version 900 Computersand Structures Inc Berkeley Calif USA 2005
[25] Computers and Structures Perform 3D Nonlinear Analysis andPerformance Assessment for 3D Structures User Guide Version 4Computers and Structures Berkeley Calif USA 2006
Shock and Vibration 15
[26] J W Wallace and J P Moehle ldquoDuctility and detailing require-ments of bearing wall buildingsrdquo Journal of Structural Engineer-ing vol 118 no 6 pp 1625ndash1644 1992
[27] P Adebar A M M Ibrahim and M Bryson ldquoTest of high-risecore wall effective stiffness for seismic analysisrdquo ACI StructuralJournal vol 104 no 5 pp 549ndash559 2007
[28] FEMA ldquoPrestandard and commentary for the seismic rehabil-itation of buildingsrdquo FEMA 356 Federal Emergency Manage-ment Agency Washington DC USA 2000
[29] LATBDSC An Alternative Procedure for Seismic Analysis andDesign of Tall Buildings Located in Los Angeles Region A Con-sensus Document Los Angeles Tall Buildings and StructuralDesign Council 2008
[30] PEERNGAData Base Pacific Earthquake Engineering Research(PEER) University of California Berkeley Calif USA 2005httppeerberkeleyedunga
[31] COSMOS Data Base ldquoConsortium of organization for strong-motion observation systemsrdquo Tech Rep University of Cali-fornia Berkeley Calif USA 1999ndash2007 httpwwwcosmos-eqorgscriptsdefaultplx
[32] K Lilhanand and W S Tseng ldquoDevelopment and applicationof realistic earthquake time histories compatible with multipledamping design spectrardquo in Proceedings of the 9th World Con-ference on Earthquake Engineering Tokyo Japan August 1988
[33] J Hancock J Watson-Lamprey N A Abrahamson et al ldquoAnimproved method of matching response spectra of recordedearthquake ground motion using waveletsrdquo Journal of Earth-quake Engineering vol 10 no 1 pp 67ndash89 2006
[34] J B Mander M J N Priestley and R Park ldquoTheoreticalstress-strain model for confined concreterdquo Journal of StructuralEngineering New York vol 114 no 8 pp 1804ndash1826 1988
[35] CTBUH Seismic Working Group CTBUH Recommendationsfor the Seismic Design of High-Rise Buildings A ConsensusDocument 2008
[36] N Satake K-I Suda T Arakawa A Sasaki and Y TamuraldquoDamping evaluation using full-scale data of buildings inJapanrdquo Journal of Structural Engineering vol 129 no 4 pp 470ndash477 2003
[37] Q Xie ldquoState of the art of buckling-restrained braces in AsiardquoJournal of Constructional Steel Research vol 61 no 6 pp 727ndash748 2005
[38] P Clark K Kasai I Aiken E Ko and I Kimura ldquoDesign proce-dures for buildings incorporating hysteretic energy dissipatingdevicesrdquo in Proceedings of the 68th Annual Convention Struc-tural Engineers Association of California Santa Barbara CalifUSA October 1999
[39] D Vafaei and R Eskandari ldquoSeismic response of mega buck-ling-restrained braces subjected to fling-step and forward-directivity near-fault ground motionsrdquo Structural Design of Talland Special Buildings vol 24 no 9 pp 672ndash686 2015
[40] L Di Sarno and A S Elnashai ldquoBracing systems for seismicretrofitting of steel framesrdquo Journal of Constructional SteelResearch vol 65 no 2 pp 452ndash465 2009
[41] A Dutta and R O Hamburger ldquoCase study of A 40-Storeybuckling-restrained braced frame building located in LosAnge-lesrdquo The Structural Design of Tall and Special Buildings vol 19no 1-2 pp 77ndash93 2010
[42] Rutherford amp Chekene ldquoPerform nonlinear component mod-elling of star seismic powercat BRBsrdquo Report to Star SeismicLLC Star Seismic LLC 2011
[43] P Dusicka A M Itani and I G Buckle ldquoCyclic response ofplate steels under large inelastic strainsrdquo Journal of Construc-tional Steel Research vol 63 no 2 pp 156ndash164 2007
[44] S A Razavi M E Shemshadian S R Mirghaderi and SAhlehagh ldquoSeismic design of buckling restrained braced frameswith reduced core lengthrdquo in Proceedings of the The StructuralEngineers World Congress Cernobbio Italy 2011
[45] S A Razavi S R Mirghaderi A Hosseini and M EShemshadian ldquoReduced length buckling restrained brace usingsteel plates as restraining segmentrdquo in Proceedings of the 15thWorld Conference on Earthquake Engineering Lisboa PurtagalSeptember 2012
[46] M E Shemshadian S A Razavi S R Mirghaderi A Hosseiniand M K Mohammadi ldquoThe advantages of reducing thelength of yielding segment in seismic performance of bucklingrestrained braced framesrdquo inProceedings of the 6th InternationalConference of Seismology and Earthquake Engineering TehranIran 2011
[47] N Ma B Wu J Zhao H Li J Ou andW Yang ldquoFull scale testof all-steel buckling restrained bracesrdquo in Proceedings of the 14thWorld Conference on Earthquake Engineering Beijing ChinaOctober 2008
[48] L Di Sarno and G Manfredi ldquoSeismic retrofitting of existingRC frames with buckling restrained bracesrdquo in Proceedings ofthe Improving the Seismic Performance of Existing Buildingsand Other Structures pp 741ndash752 San Francisco Calif USADecember 2009
[49] S Ahlehagh Improvement of the special concentrically bracedsteel frames behaviour by employing balanced braces [MSthesis] University of Tehran Tehran Iran 2008
[50] R Tremblay P Bolduc R Neville and R DeVall ldquoSeismic test-ing and performance of buckling-restrained bracing systemsrdquoCanadian Journal of Civil Engineering vol 33 no 2 pp 183ndash1982006
Figure 17 Moment and shear envelope in one typical column
minus20 minus10 00 10 20
Base
shea
r (kN
)
Top displacement (m)
Option-1Option-2
Option-3Option-4
300E + 04
200E + 04
100E + 04
000E + 00
minus100E + 04
minus200E + 04
minus300E + 04
Figure 18 Base shear versus top displacement relationship in firstmode load pattern
displacement is compared in Figure 18 It can be seen that thiscurve is flag shaped for Option-1 whereas it is bilinear pinch-ing type in Options-2ndash4There is no permanent deformationin controlled structure and flag shaped hysteresis behaviouris observed The same behaviour was observed during testconducted on a large-scale model of a concrete shear wallfrom the core of a high-rise building in the study of Adebar etal [27] The combination of low percentage of vertical rein-forcement and large axial compression force due to gravity
loads (axial force(concrete 28 days cylinder strength times grossarea ofwall)gt 01) caused the flexural cracks to closewhen thelateral load was removed In Options-2ndash4 small permanentdeformation (residual displacement) is observed This isbecause of the plastification of BRBs as well as transfer of themoment demand from shear wall to columns in the form ofaxial push-pull
8 Conclusions
(i) In this study different options of location of BRBsare investigated for a 40-story case study buildingThe locations of BRBs are identified based on theDBE elastic racking shear deformation and shear andbending moment demands in dominant 2nd and 3rdmodes NLRHA is then performed for seven sets ofspectrally matched target time histories and resultsare compared for different options
(ii) In all options shear force demands bending momentat mid height displacement demand racking sheardeformation demand and rotation demand in cou-pling beams are reduced by 10 45 45 45 and40 respectively in comparison to the controlledstructure
(iii) Rotational demand in the core wall at base level isreduced by 99 57 and 93 in Option-2 Option-3 and Option-4 respectively in comparison toOption-1Whereas energy dissipated by the core wallis reduced by around 250 in the corewall in compar-ison to the controlled structure Rotational demandand energy dissipation are measure of damage in thecore wall Thus damage can be significantly reducedby installation of BRBs
14 Shock and Vibration
(iv) All BRBs options are effective for bending momentreduction at mid height displacement and rackingshear deformation demands along the wall heightand rotation demand at the base of the wall and incoupling beams above the mid height of the build-ing However Option-4 in which BRBs are installedbetween peripheral columns and central corewall andcut in shear walls based on the maximum shear forceand bending moment leads to the highest reductionThis is because of the early yielding of the interiorbraces
(v) Thiswork is equally important for academia and prac-tising engineers especially those working in the fieldof performance based design of the high-rise build-ings in the commercial consultancy This will helpthem to locate BRBs at appropriate locations whiledesigning their buildings in an optimal way
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] International Conference of Building Officials Uniform Build-ing Code vol 2 International Conference of Building OfficialsWhittier Calif USA 1997
[2] J Maffei and N Yuen ldquoSeismic performance and designrequirements for high rise buildingsrdquo Structural Magazine pp28ndash32 2007
[3] J P Moehle ldquoPerformance-based seismic design of tall build-ings in the USrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[4] CEN EC8 Design of Structures for Earthquake ResistanceEuropean Committee for Standardization Brussels Belgium2004
[5] NZS 3101 Part 12006 Concrete Structures Standards NewZealand Standards New Zealand Wellington New Zealand2006
[6] T Paulay and M J N Priestley Seismic Design of ReinforcedConcrete and Masonry Buildings Wiley Hoboken NJ USA1992
[7] M Panagiotou J I Restrepo and J P Conte ldquoShake table test ofa 7-story full scale reinforced concrete structural wall buildingslice phase I rectangular wallrdquo Report SSRP 07-07 Departmentof Structural Engineering University of California San DiegoSan Diego Calif USA 2007
[8] Canadian Standard Association CSA Standard A233-04Design of Concrete Structures Canadian Standard AssociationRexdale Canada 2005
[9] R Klemencic J A Fry J D Hooper and B G MorgenldquoPerformance-based design of ductile concrete core wall build-ingsmdashissues to consider before detailed analysisrdquoTheStructuralDesign of Tall and Special Buildings vol 16 no 5 pp 599ndash6142007
[10] R Klemencic ldquoPerformance based seismic designmdashrisingrdquoStructural Magazine 2008 httpwwwstructuremagorgwp-contentuploads201408C-StructuralPractices-Klemencic-June081pdf
[11] A Zekioglu M Willford L Jin and M Melek ldquoCase studyusing the Los Angeles tall buildings structural design councilguidelines 40-storey concrete core wall buildingrdquo StructuralDesign of Tall and Special Buildings vol 16 no 5 pp 583ndash5972007
[12] B R Rad and P Adebar ldquoDynamic shear amplification inhigh-rise concrete walls effect of multiple flexural hinges andshear crackingrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[13] M Panagiotou and J I Restrepo ldquoDual-plastic hinge designconcept for reducing higher-mode effects on high-rise can-tilever wall buildingsrdquo Earthquake Engineering and StructuralDynamics vol 38 no 12 pp 1359ndash1380 2009
[14] M Ahmed and P Warnitchai ldquoReduction of inelastic seismicdemands by inducing plastic hinges at effective locationsrdquoin Proceedings of the 3rd Asian Conference on EarthquakeEngineering (ACEE rsquo10) Bangkok Thailand December 2010
[15] A Munir and P Warnitchai ldquoThe cause of unproportion-ately large higher mode contributions in the inelastic seismicresponses of high-rise core-wall buildingsrdquo Earthquake Engi-neering amp Structural Dynamics vol 41 no 15 pp 2195ndash22142012
[16] A Munir and P Warnitchai ldquoOptimal reduction of inelasticseismic demands in high-rise reinforced concrete core wallbuildings using energy-dissipating devicesrdquo Structural Design ofTall and Special Buildings vol 22 no 7 pp 543ndash568 2013
[17] M C Constantinou and M D Symans ldquoExperimental andanalytical investigation of seismic response of structures withsupplemental fluid viscous dampersrdquo NCEER Reports 92-0032State University of New York at Buffalo Buffalo NY USA 1992
[18] A SWhittaker V V Bertero C LThompson and L J AlonsoldquoSeismic testing of steel plate energy dissipation devicesrdquoEarthquake Spectra vol 7 no 4 pp 563ndash604 1991
[19] G W Housner L A Bergman T K Caughey et al ldquoStruc-tural control past present and futurerdquo Journal of EngineeringMechanics vol 123 no 9 pp 897ndash971 1997
[20] M D Symans F A Charney A S Whittaker et al ldquoEnergydissipation systems for seismic applications current practiceand recent developmentsrdquo Journal of Structural Engineering vol134 no 1 pp 3ndash21 2008
[21] C J Black N Makris and I D Aiken ldquoComponent testingseismic evaluation and characterization of buckling-restrainedbracesrdquo Journal of Structural Engineering vol 130 no 6 pp880ndash894 2004
[22] S Keten A performance based approach for seismic designwith hysteretic dampers [MS thesis] Massachusetts Institute ofTechnology (MIT) 2006 httpdspacemitedubitstreamhan-dle172113459571252112-MITpdfsequence=2
[23] N Anwar J A Sy T H Aung and D Rayamajhi ldquoFirstapplication of buckling restraint brace system in Philippines ina 50-story building with ductile core wall and PT slab systemrdquoin Proceedings of the 9th International Conference on UrbanEarthquake Engineering and the 4th Asia Conference on Earth-quake Engineering Tokyo Institute of Technology Tokyo JapanMarch 2012
[24] Computers and Structures Inc ETABS Extended 3D Analysis ofBuilding Systems Software Nonlinear Version 900 Computersand Structures Inc Berkeley Calif USA 2005
[25] Computers and Structures Perform 3D Nonlinear Analysis andPerformance Assessment for 3D Structures User Guide Version 4Computers and Structures Berkeley Calif USA 2006
Shock and Vibration 15
[26] J W Wallace and J P Moehle ldquoDuctility and detailing require-ments of bearing wall buildingsrdquo Journal of Structural Engineer-ing vol 118 no 6 pp 1625ndash1644 1992
[27] P Adebar A M M Ibrahim and M Bryson ldquoTest of high-risecore wall effective stiffness for seismic analysisrdquo ACI StructuralJournal vol 104 no 5 pp 549ndash559 2007
[28] FEMA ldquoPrestandard and commentary for the seismic rehabil-itation of buildingsrdquo FEMA 356 Federal Emergency Manage-ment Agency Washington DC USA 2000
[29] LATBDSC An Alternative Procedure for Seismic Analysis andDesign of Tall Buildings Located in Los Angeles Region A Con-sensus Document Los Angeles Tall Buildings and StructuralDesign Council 2008
[30] PEERNGAData Base Pacific Earthquake Engineering Research(PEER) University of California Berkeley Calif USA 2005httppeerberkeleyedunga
[31] COSMOS Data Base ldquoConsortium of organization for strong-motion observation systemsrdquo Tech Rep University of Cali-fornia Berkeley Calif USA 1999ndash2007 httpwwwcosmos-eqorgscriptsdefaultplx
[32] K Lilhanand and W S Tseng ldquoDevelopment and applicationof realistic earthquake time histories compatible with multipledamping design spectrardquo in Proceedings of the 9th World Con-ference on Earthquake Engineering Tokyo Japan August 1988
[33] J Hancock J Watson-Lamprey N A Abrahamson et al ldquoAnimproved method of matching response spectra of recordedearthquake ground motion using waveletsrdquo Journal of Earth-quake Engineering vol 10 no 1 pp 67ndash89 2006
[34] J B Mander M J N Priestley and R Park ldquoTheoreticalstress-strain model for confined concreterdquo Journal of StructuralEngineering New York vol 114 no 8 pp 1804ndash1826 1988
[35] CTBUH Seismic Working Group CTBUH Recommendationsfor the Seismic Design of High-Rise Buildings A ConsensusDocument 2008
[36] N Satake K-I Suda T Arakawa A Sasaki and Y TamuraldquoDamping evaluation using full-scale data of buildings inJapanrdquo Journal of Structural Engineering vol 129 no 4 pp 470ndash477 2003
[37] Q Xie ldquoState of the art of buckling-restrained braces in AsiardquoJournal of Constructional Steel Research vol 61 no 6 pp 727ndash748 2005
[38] P Clark K Kasai I Aiken E Ko and I Kimura ldquoDesign proce-dures for buildings incorporating hysteretic energy dissipatingdevicesrdquo in Proceedings of the 68th Annual Convention Struc-tural Engineers Association of California Santa Barbara CalifUSA October 1999
[39] D Vafaei and R Eskandari ldquoSeismic response of mega buck-ling-restrained braces subjected to fling-step and forward-directivity near-fault ground motionsrdquo Structural Design of Talland Special Buildings vol 24 no 9 pp 672ndash686 2015
[40] L Di Sarno and A S Elnashai ldquoBracing systems for seismicretrofitting of steel framesrdquo Journal of Constructional SteelResearch vol 65 no 2 pp 452ndash465 2009
[41] A Dutta and R O Hamburger ldquoCase study of A 40-Storeybuckling-restrained braced frame building located in LosAnge-lesrdquo The Structural Design of Tall and Special Buildings vol 19no 1-2 pp 77ndash93 2010
[42] Rutherford amp Chekene ldquoPerform nonlinear component mod-elling of star seismic powercat BRBsrdquo Report to Star SeismicLLC Star Seismic LLC 2011
[43] P Dusicka A M Itani and I G Buckle ldquoCyclic response ofplate steels under large inelastic strainsrdquo Journal of Construc-tional Steel Research vol 63 no 2 pp 156ndash164 2007
[44] S A Razavi M E Shemshadian S R Mirghaderi and SAhlehagh ldquoSeismic design of buckling restrained braced frameswith reduced core lengthrdquo in Proceedings of the The StructuralEngineers World Congress Cernobbio Italy 2011
[45] S A Razavi S R Mirghaderi A Hosseini and M EShemshadian ldquoReduced length buckling restrained brace usingsteel plates as restraining segmentrdquo in Proceedings of the 15thWorld Conference on Earthquake Engineering Lisboa PurtagalSeptember 2012
[46] M E Shemshadian S A Razavi S R Mirghaderi A Hosseiniand M K Mohammadi ldquoThe advantages of reducing thelength of yielding segment in seismic performance of bucklingrestrained braced framesrdquo inProceedings of the 6th InternationalConference of Seismology and Earthquake Engineering TehranIran 2011
[47] N Ma B Wu J Zhao H Li J Ou andW Yang ldquoFull scale testof all-steel buckling restrained bracesrdquo in Proceedings of the 14thWorld Conference on Earthquake Engineering Beijing ChinaOctober 2008
[48] L Di Sarno and G Manfredi ldquoSeismic retrofitting of existingRC frames with buckling restrained bracesrdquo in Proceedings ofthe Improving the Seismic Performance of Existing Buildingsand Other Structures pp 741ndash752 San Francisco Calif USADecember 2009
[49] S Ahlehagh Improvement of the special concentrically bracedsteel frames behaviour by employing balanced braces [MSthesis] University of Tehran Tehran Iran 2008
[50] R Tremblay P Bolduc R Neville and R DeVall ldquoSeismic test-ing and performance of buckling-restrained bracing systemsrdquoCanadian Journal of Civil Engineering vol 33 no 2 pp 183ndash1982006
(iv) All BRBs options are effective for bending momentreduction at mid height displacement and rackingshear deformation demands along the wall heightand rotation demand at the base of the wall and incoupling beams above the mid height of the build-ing However Option-4 in which BRBs are installedbetween peripheral columns and central corewall andcut in shear walls based on the maximum shear forceand bending moment leads to the highest reductionThis is because of the early yielding of the interiorbraces
(v) Thiswork is equally important for academia and prac-tising engineers especially those working in the fieldof performance based design of the high-rise build-ings in the commercial consultancy This will helpthem to locate BRBs at appropriate locations whiledesigning their buildings in an optimal way
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] International Conference of Building Officials Uniform Build-ing Code vol 2 International Conference of Building OfficialsWhittier Calif USA 1997
[2] J Maffei and N Yuen ldquoSeismic performance and designrequirements for high rise buildingsrdquo Structural Magazine pp28ndash32 2007
[3] J P Moehle ldquoPerformance-based seismic design of tall build-ings in the USrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[4] CEN EC8 Design of Structures for Earthquake ResistanceEuropean Committee for Standardization Brussels Belgium2004
[5] NZS 3101 Part 12006 Concrete Structures Standards NewZealand Standards New Zealand Wellington New Zealand2006
[6] T Paulay and M J N Priestley Seismic Design of ReinforcedConcrete and Masonry Buildings Wiley Hoboken NJ USA1992
[7] M Panagiotou J I Restrepo and J P Conte ldquoShake table test ofa 7-story full scale reinforced concrete structural wall buildingslice phase I rectangular wallrdquo Report SSRP 07-07 Departmentof Structural Engineering University of California San DiegoSan Diego Calif USA 2007
[8] Canadian Standard Association CSA Standard A233-04Design of Concrete Structures Canadian Standard AssociationRexdale Canada 2005
[9] R Klemencic J A Fry J D Hooper and B G MorgenldquoPerformance-based design of ductile concrete core wall build-ingsmdashissues to consider before detailed analysisrdquoTheStructuralDesign of Tall and Special Buildings vol 16 no 5 pp 599ndash6142007
[10] R Klemencic ldquoPerformance based seismic designmdashrisingrdquoStructural Magazine 2008 httpwwwstructuremagorgwp-contentuploads201408C-StructuralPractices-Klemencic-June081pdf
[11] A Zekioglu M Willford L Jin and M Melek ldquoCase studyusing the Los Angeles tall buildings structural design councilguidelines 40-storey concrete core wall buildingrdquo StructuralDesign of Tall and Special Buildings vol 16 no 5 pp 583ndash5972007
[12] B R Rad and P Adebar ldquoDynamic shear amplification inhigh-rise concrete walls effect of multiple flexural hinges andshear crackingrdquo in Proceedings of the 14th World Conference onEarthquake Engineering Beijing China October 2008
[13] M Panagiotou and J I Restrepo ldquoDual-plastic hinge designconcept for reducing higher-mode effects on high-rise can-tilever wall buildingsrdquo Earthquake Engineering and StructuralDynamics vol 38 no 12 pp 1359ndash1380 2009
[14] M Ahmed and P Warnitchai ldquoReduction of inelastic seismicdemands by inducing plastic hinges at effective locationsrdquoin Proceedings of the 3rd Asian Conference on EarthquakeEngineering (ACEE rsquo10) Bangkok Thailand December 2010
[15] A Munir and P Warnitchai ldquoThe cause of unproportion-ately large higher mode contributions in the inelastic seismicresponses of high-rise core-wall buildingsrdquo Earthquake Engi-neering amp Structural Dynamics vol 41 no 15 pp 2195ndash22142012
[16] A Munir and P Warnitchai ldquoOptimal reduction of inelasticseismic demands in high-rise reinforced concrete core wallbuildings using energy-dissipating devicesrdquo Structural Design ofTall and Special Buildings vol 22 no 7 pp 543ndash568 2013
[17] M C Constantinou and M D Symans ldquoExperimental andanalytical investigation of seismic response of structures withsupplemental fluid viscous dampersrdquo NCEER Reports 92-0032State University of New York at Buffalo Buffalo NY USA 1992
[18] A SWhittaker V V Bertero C LThompson and L J AlonsoldquoSeismic testing of steel plate energy dissipation devicesrdquoEarthquake Spectra vol 7 no 4 pp 563ndash604 1991
[19] G W Housner L A Bergman T K Caughey et al ldquoStruc-tural control past present and futurerdquo Journal of EngineeringMechanics vol 123 no 9 pp 897ndash971 1997
[20] M D Symans F A Charney A S Whittaker et al ldquoEnergydissipation systems for seismic applications current practiceand recent developmentsrdquo Journal of Structural Engineering vol134 no 1 pp 3ndash21 2008
[21] C J Black N Makris and I D Aiken ldquoComponent testingseismic evaluation and characterization of buckling-restrainedbracesrdquo Journal of Structural Engineering vol 130 no 6 pp880ndash894 2004
[22] S Keten A performance based approach for seismic designwith hysteretic dampers [MS thesis] Massachusetts Institute ofTechnology (MIT) 2006 httpdspacemitedubitstreamhan-dle172113459571252112-MITpdfsequence=2
[23] N Anwar J A Sy T H Aung and D Rayamajhi ldquoFirstapplication of buckling restraint brace system in Philippines ina 50-story building with ductile core wall and PT slab systemrdquoin Proceedings of the 9th International Conference on UrbanEarthquake Engineering and the 4th Asia Conference on Earth-quake Engineering Tokyo Institute of Technology Tokyo JapanMarch 2012
[24] Computers and Structures Inc ETABS Extended 3D Analysis ofBuilding Systems Software Nonlinear Version 900 Computersand Structures Inc Berkeley Calif USA 2005
[25] Computers and Structures Perform 3D Nonlinear Analysis andPerformance Assessment for 3D Structures User Guide Version 4Computers and Structures Berkeley Calif USA 2006
Shock and Vibration 15
[26] J W Wallace and J P Moehle ldquoDuctility and detailing require-ments of bearing wall buildingsrdquo Journal of Structural Engineer-ing vol 118 no 6 pp 1625ndash1644 1992
[27] P Adebar A M M Ibrahim and M Bryson ldquoTest of high-risecore wall effective stiffness for seismic analysisrdquo ACI StructuralJournal vol 104 no 5 pp 549ndash559 2007
[28] FEMA ldquoPrestandard and commentary for the seismic rehabil-itation of buildingsrdquo FEMA 356 Federal Emergency Manage-ment Agency Washington DC USA 2000
[29] LATBDSC An Alternative Procedure for Seismic Analysis andDesign of Tall Buildings Located in Los Angeles Region A Con-sensus Document Los Angeles Tall Buildings and StructuralDesign Council 2008
[30] PEERNGAData Base Pacific Earthquake Engineering Research(PEER) University of California Berkeley Calif USA 2005httppeerberkeleyedunga
[31] COSMOS Data Base ldquoConsortium of organization for strong-motion observation systemsrdquo Tech Rep University of Cali-fornia Berkeley Calif USA 1999ndash2007 httpwwwcosmos-eqorgscriptsdefaultplx
[32] K Lilhanand and W S Tseng ldquoDevelopment and applicationof realistic earthquake time histories compatible with multipledamping design spectrardquo in Proceedings of the 9th World Con-ference on Earthquake Engineering Tokyo Japan August 1988
[33] J Hancock J Watson-Lamprey N A Abrahamson et al ldquoAnimproved method of matching response spectra of recordedearthquake ground motion using waveletsrdquo Journal of Earth-quake Engineering vol 10 no 1 pp 67ndash89 2006
[34] J B Mander M J N Priestley and R Park ldquoTheoreticalstress-strain model for confined concreterdquo Journal of StructuralEngineering New York vol 114 no 8 pp 1804ndash1826 1988
[35] CTBUH Seismic Working Group CTBUH Recommendationsfor the Seismic Design of High-Rise Buildings A ConsensusDocument 2008
[36] N Satake K-I Suda T Arakawa A Sasaki and Y TamuraldquoDamping evaluation using full-scale data of buildings inJapanrdquo Journal of Structural Engineering vol 129 no 4 pp 470ndash477 2003
[37] Q Xie ldquoState of the art of buckling-restrained braces in AsiardquoJournal of Constructional Steel Research vol 61 no 6 pp 727ndash748 2005
[38] P Clark K Kasai I Aiken E Ko and I Kimura ldquoDesign proce-dures for buildings incorporating hysteretic energy dissipatingdevicesrdquo in Proceedings of the 68th Annual Convention Struc-tural Engineers Association of California Santa Barbara CalifUSA October 1999
[39] D Vafaei and R Eskandari ldquoSeismic response of mega buck-ling-restrained braces subjected to fling-step and forward-directivity near-fault ground motionsrdquo Structural Design of Talland Special Buildings vol 24 no 9 pp 672ndash686 2015
[40] L Di Sarno and A S Elnashai ldquoBracing systems for seismicretrofitting of steel framesrdquo Journal of Constructional SteelResearch vol 65 no 2 pp 452ndash465 2009
[41] A Dutta and R O Hamburger ldquoCase study of A 40-Storeybuckling-restrained braced frame building located in LosAnge-lesrdquo The Structural Design of Tall and Special Buildings vol 19no 1-2 pp 77ndash93 2010
[42] Rutherford amp Chekene ldquoPerform nonlinear component mod-elling of star seismic powercat BRBsrdquo Report to Star SeismicLLC Star Seismic LLC 2011
[43] P Dusicka A M Itani and I G Buckle ldquoCyclic response ofplate steels under large inelastic strainsrdquo Journal of Construc-tional Steel Research vol 63 no 2 pp 156ndash164 2007
[44] S A Razavi M E Shemshadian S R Mirghaderi and SAhlehagh ldquoSeismic design of buckling restrained braced frameswith reduced core lengthrdquo in Proceedings of the The StructuralEngineers World Congress Cernobbio Italy 2011
[45] S A Razavi S R Mirghaderi A Hosseini and M EShemshadian ldquoReduced length buckling restrained brace usingsteel plates as restraining segmentrdquo in Proceedings of the 15thWorld Conference on Earthquake Engineering Lisboa PurtagalSeptember 2012
[46] M E Shemshadian S A Razavi S R Mirghaderi A Hosseiniand M K Mohammadi ldquoThe advantages of reducing thelength of yielding segment in seismic performance of bucklingrestrained braced framesrdquo inProceedings of the 6th InternationalConference of Seismology and Earthquake Engineering TehranIran 2011
[47] N Ma B Wu J Zhao H Li J Ou andW Yang ldquoFull scale testof all-steel buckling restrained bracesrdquo in Proceedings of the 14thWorld Conference on Earthquake Engineering Beijing ChinaOctober 2008
[48] L Di Sarno and G Manfredi ldquoSeismic retrofitting of existingRC frames with buckling restrained bracesrdquo in Proceedings ofthe Improving the Seismic Performance of Existing Buildingsand Other Structures pp 741ndash752 San Francisco Calif USADecember 2009
[49] S Ahlehagh Improvement of the special concentrically bracedsteel frames behaviour by employing balanced braces [MSthesis] University of Tehran Tehran Iran 2008
[50] R Tremblay P Bolduc R Neville and R DeVall ldquoSeismic test-ing and performance of buckling-restrained bracing systemsrdquoCanadian Journal of Civil Engineering vol 33 no 2 pp 183ndash1982006
[26] J W Wallace and J P Moehle ldquoDuctility and detailing require-ments of bearing wall buildingsrdquo Journal of Structural Engineer-ing vol 118 no 6 pp 1625ndash1644 1992
[27] P Adebar A M M Ibrahim and M Bryson ldquoTest of high-risecore wall effective stiffness for seismic analysisrdquo ACI StructuralJournal vol 104 no 5 pp 549ndash559 2007
[28] FEMA ldquoPrestandard and commentary for the seismic rehabil-itation of buildingsrdquo FEMA 356 Federal Emergency Manage-ment Agency Washington DC USA 2000
[29] LATBDSC An Alternative Procedure for Seismic Analysis andDesign of Tall Buildings Located in Los Angeles Region A Con-sensus Document Los Angeles Tall Buildings and StructuralDesign Council 2008
[30] PEERNGAData Base Pacific Earthquake Engineering Research(PEER) University of California Berkeley Calif USA 2005httppeerberkeleyedunga
[31] COSMOS Data Base ldquoConsortium of organization for strong-motion observation systemsrdquo Tech Rep University of Cali-fornia Berkeley Calif USA 1999ndash2007 httpwwwcosmos-eqorgscriptsdefaultplx
[32] K Lilhanand and W S Tseng ldquoDevelopment and applicationof realistic earthquake time histories compatible with multipledamping design spectrardquo in Proceedings of the 9th World Con-ference on Earthquake Engineering Tokyo Japan August 1988
[33] J Hancock J Watson-Lamprey N A Abrahamson et al ldquoAnimproved method of matching response spectra of recordedearthquake ground motion using waveletsrdquo Journal of Earth-quake Engineering vol 10 no 1 pp 67ndash89 2006
[34] J B Mander M J N Priestley and R Park ldquoTheoreticalstress-strain model for confined concreterdquo Journal of StructuralEngineering New York vol 114 no 8 pp 1804ndash1826 1988
[35] CTBUH Seismic Working Group CTBUH Recommendationsfor the Seismic Design of High-Rise Buildings A ConsensusDocument 2008
[36] N Satake K-I Suda T Arakawa A Sasaki and Y TamuraldquoDamping evaluation using full-scale data of buildings inJapanrdquo Journal of Structural Engineering vol 129 no 4 pp 470ndash477 2003
[37] Q Xie ldquoState of the art of buckling-restrained braces in AsiardquoJournal of Constructional Steel Research vol 61 no 6 pp 727ndash748 2005
[38] P Clark K Kasai I Aiken E Ko and I Kimura ldquoDesign proce-dures for buildings incorporating hysteretic energy dissipatingdevicesrdquo in Proceedings of the 68th Annual Convention Struc-tural Engineers Association of California Santa Barbara CalifUSA October 1999
[39] D Vafaei and R Eskandari ldquoSeismic response of mega buck-ling-restrained braces subjected to fling-step and forward-directivity near-fault ground motionsrdquo Structural Design of Talland Special Buildings vol 24 no 9 pp 672ndash686 2015
[40] L Di Sarno and A S Elnashai ldquoBracing systems for seismicretrofitting of steel framesrdquo Journal of Constructional SteelResearch vol 65 no 2 pp 452ndash465 2009
[41] A Dutta and R O Hamburger ldquoCase study of A 40-Storeybuckling-restrained braced frame building located in LosAnge-lesrdquo The Structural Design of Tall and Special Buildings vol 19no 1-2 pp 77ndash93 2010
[42] Rutherford amp Chekene ldquoPerform nonlinear component mod-elling of star seismic powercat BRBsrdquo Report to Star SeismicLLC Star Seismic LLC 2011
[43] P Dusicka A M Itani and I G Buckle ldquoCyclic response ofplate steels under large inelastic strainsrdquo Journal of Construc-tional Steel Research vol 63 no 2 pp 156ndash164 2007
[44] S A Razavi M E Shemshadian S R Mirghaderi and SAhlehagh ldquoSeismic design of buckling restrained braced frameswith reduced core lengthrdquo in Proceedings of the The StructuralEngineers World Congress Cernobbio Italy 2011
[45] S A Razavi S R Mirghaderi A Hosseini and M EShemshadian ldquoReduced length buckling restrained brace usingsteel plates as restraining segmentrdquo in Proceedings of the 15thWorld Conference on Earthquake Engineering Lisboa PurtagalSeptember 2012
[46] M E Shemshadian S A Razavi S R Mirghaderi A Hosseiniand M K Mohammadi ldquoThe advantages of reducing thelength of yielding segment in seismic performance of bucklingrestrained braced framesrdquo inProceedings of the 6th InternationalConference of Seismology and Earthquake Engineering TehranIran 2011
[47] N Ma B Wu J Zhao H Li J Ou andW Yang ldquoFull scale testof all-steel buckling restrained bracesrdquo in Proceedings of the 14thWorld Conference on Earthquake Engineering Beijing ChinaOctober 2008
[48] L Di Sarno and G Manfredi ldquoSeismic retrofitting of existingRC frames with buckling restrained bracesrdquo in Proceedings ofthe Improving the Seismic Performance of Existing Buildingsand Other Structures pp 741ndash752 San Francisco Calif USADecember 2009
[49] S Ahlehagh Improvement of the special concentrically bracedsteel frames behaviour by employing balanced braces [MSthesis] University of Tehran Tehran Iran 2008
[50] R Tremblay P Bolduc R Neville and R DeVall ldquoSeismic test-ing and performance of buckling-restrained bracing systemsrdquoCanadian Journal of Civil Engineering vol 33 no 2 pp 183ndash1982006
![Chapter Propagation Buckling of Subsea Pipelines and Pipe ...investigates the effect of corrosion in the propagation buckling of subsea pipelines. Buckle arrestors [1, 18], pipe-in-pipe](https://static.documents.pub/doc/80x56/6129eddf23d782008d4867f7/chapter-propagation-buckling-of-subsea-pipelines-and-pipe-investigates-the-effect.jpg)
