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1International Conference on Earthquake Analysis and Design of Structures (EQADS 2011), December 1-3, 2011 Department of Civil Engineering, PSG College of Technology,
Coimbatore, Tamilnadu, India
Dr.AjaySharmaAssociateProfessor
DepartmentofStructuralEngineering,FacultyofEngineering,J.N.V.UniversityJodhpur
2Overviewy Introductiony BaseisolatedBuildingy SemiactiveDampers
PredictiveControlledSemiactiveFrictionDamperResettingSemiactiveStiffnessDamperMRDamper
y NumericalStudyNumericalStudyy Conclusions
2
3Introductiony Baseisolationy NearfieldEarthquakesy SemiactiveDampersy StructuralResponseBasedisplacementAbs.FlooraccelerationBaseShearBaseShearStoreyDrift
3
4BaseisolatedBuilding
4
5NearfieldEarthquakes
15202530 Sylmar
Rinaldi Kobe Jiji
Spectral acceleration (m/s2)
2.53.03.54.0
0.1 1 1005
1015
Spectral Velocity (m/s)
Erzincan
Time(sec)
0.1 1 100.00.51.01.52.0
0.8
1.0
Time (sec)
Spectral displacement(m)
5
0.1 1 10
0.0
0.2
0.4
0.6
5 percent damping
Time (sec)Figure 4: Response Spectrums of the Earthquakes
6SEMIACTIVEDAMPERSPredictiveControlledSemiactiveFrictionDamper
L [2004] d l d i ti f i ti d hi h i bl t dj t itLu [2004] developed a semi-active friction damper which is able to adjust itsslip force by controlling its clamping force in real-time in response to astructures motion during an earthquake such that it always remains in slipstate. The semiactive friction damper utilizes the control named predictivecontrol.
( ) ( ) ( ) ( )gz t Az t Bu t Ew t= + +The force vector u (t) depends not only on the damper properties (the friction
coefficient, time-varying clamping forces and dampers stiffness, etc.), butalso on the structural dynamic response and can be expressed as
( ) ( ) ( )( ) [ { ( ) ( 1)} ( 1)]i g d i d i d i iu t k z t z t u t= +
( ) ( ) ( ) ( )g
6
7R tti S i ti Stiff D
SEMIACTIVEDAMPERSResettingSemiactiveStiffnessDamper
Yang et al., [4] derived a general resetting control law based on theLyapunov theory, which resets the RSASD stiffness at each momentwhen the relative velocity cross the damper reaches zero. When thevalve is closed the damper serves as a stiffness element with anvalve is closed, the damper serves as a stiffness element with aneffective stiffness kd provided by the bulk modulus of the fluid inside.
( ) ( )i d pu t k x x=
7
8SEMIACTIVEDAMPERSMRDMRDampers
820 Ton Magnetorheological fluid Damper (Yang and Spencer 2002)
9NUMERICALSTUDYThe overall governing equation of motion of complete structures can be written for the condensed linear-elastic superstructure with controlled isolated base, th ti f ti ithe equation of motion is
{ }0 0
0 0
00b b b bb b
M M R C K UU UR M R M R M C K UU U
M RU
+ + + + +
9
{ }gC bB
Uf R M R Mf
+ + = +
10
46
4 3 5
S y lm a r X d ire c t io n Y d ire c tio n4 .8 6 4 .7 44 5 6
-4-202
4 .3 5
F P S B a s e - is o la te d S A F r ic tio n
4 .5 6
0246
4.35 Sylmar X direction Y direction4.74.74
4.85
0369
Base-isolated M R Damper4.354.91
7.91
4.74
3 6 9 12-4-20
3 6 9 12 15FPS
Basr-isolated SA Stiffness
10
3 6 9 12-6-30
3 6 9 12 15
Time-history response of Top floor absolute acceleration of the Base-isolated Building
11
0.6
nt (m
)
S ylm ar X direction Y direction B ase-isola tedS A F ric tion
3 6 9 12-0 .6
-0 .3
0.0
0.3
3 6 9 12 15
B
ase
disp
lace
me n S A F ric tion
T im e (sec) T im e (sec)
0 .5020 .47 8 0 .35 9
0 .41 9
0 .3
0 .6 X -D irectionSylm ar Y -D irection B ase-isola ted S A S tiffness
3 6 9 120.6
0 .3
0 .0
3 6 9 12 150 .5 0 2
0 .4 7 3 0 .3 6 10 .4 1 9
0 00 .30 .60 .9
Y -D irec tion B ase-iso la tedM R D am p er
X -D irec tionS ylm ar
11
3 6 9 1 20 .60 .30 .0
3 6 9 1 2 1 50 .5 0 2
0 .3 4 8 0 .1 6 3 0 .4 1 9
Time-history response of Base displacement of the Base-isolated Building
12
5 0 0 0 07 5 0 2 0
6 8 0 9 0 5 6 8 2 0
3 5 5 6 0
B ase-iso la ted M R D am p er
3 6 9 1 2
5 0 0 0 0
0
3 6 9 1 2 1 5
3 5 5 6 0
0
50000
ear (
kN)
3 6 9 12
-50000
0
3 6 9 12 15
75020 7821056820
54300
T ime (sec)T ime (sec)
Bas
e sh
e
Base-isolated SA stiffness
0
500007 5 0 2 0
6 8 0 9 0 5 6 8 2 0
3 5 5 6 0
B ase-isolated M R D am per
12
3 6 9 12
50000
3 6 9 12 15
Time-history response of Base Shear of the Base-isolated Building
13
0.005
0.010 Base-isolatedSA Friction
Sylmar X direction Y direction
3 6 9 12-0.010
-0.005
0.000
3 6 9 12 150.0094 0.0103
0.00850.0085
0.000
0.005
0.010Sylmar
ft (m
)
X direction Y direction
3 6 9 12-0.010
-0.005
3 6 9 12 15
St
ory
drif
T ime (sec) Time (sec)
0.0094 0.00990.0085 0.0082 Base-isolated
SA Stiffness
.000
.005
.010 Sylmar X direction Y direction Base-isolated MR Damper
13
3 6 9 12.010
.005
3 6 9 12 150.0094 0.0068 0.0085
0.0051
Time-history response of Storey Drift of the Base-isolated Building
14
PeakValuesofStructuralParametersunderdifferentconditions
Peak Values Condition Sylmar Rinaldi Kobe Jiji Erzincan
Base Shear (kN)
Fixed 199205 265628 214740 127738 123116
Isolated 75048.49 60738.5 28541.09 107173.5 69143.18
SA Friction Damper 80990.78 68797.65 32215.29 106060.9 73976.71
SA Stiffness Damper 78239.76 64340.41 30660.58 98092.56 71141.35
MR Damper 68120.14 65835.9 32245.36 75532.76 60644.48
Isolated 0.50179 0.37117 0.21626 0.78836 0.50646
SA F i i
14
Base Displacement (m)
SA Friction Damper 0.47808 0.37882 0.20293 0.67445 0.47841
SA Stiffness Damper 0.4726 0.364 0.20138 0.62836 0.466
MR Damper 0.34822 0.32728 0.1443 0.48577 0.33857
15
Fixed 0.04545 0.09176 0.08768 0.03696 0.03784
Isolated 0.016226 0.015635 0.009769 0.024566 0.016753
Story Drift (m) SA Friction Damper 0.018281 0.016773 0.010368 0.022501 0.018079
SA Stiffness Damper 0.017108 0.016239 0.010037 0.020408 0.017348
MR Damper 0.016207 0.015436 0.015339 0.01625 0.01463
Abs. Floor Acceleration (m/s2)
Fixed 17.842 27.518 27.059 11.582 11.125
Isolated 4.5388 7.5424 5.1293 3.5483 2.5505
SA Friction Damper 4.873007 5.428201 3.497105 5.509789 2.73764
SA S iff D 4 848028 5 419945 3 504952 5 537238 2 642188
15
SA Stiffness Damper 4.848028 5.419945 3.504952 5.537238 2.642188
MR Damper 7.916139 5.853629 5.88858 4.71399 3.461321
16
RMS Base Displacement (m)
Isolated 0.15429 0.08142 0.04227 0.2794 0.14988
SA Friction Damper 0.13568 0.08139 0.04264 0.21977 0.1327
SA Stiffness Damper 0.12391 0.07221 0.04147 0.20515 0.12508
MR Damper 0.06749 0.05924 0.03312 0.12391 0.08393
Fixed 2.267 5.681 5.165 2.507 2.379
Isolated 0.915891 0.795738 0.865654 1.840038 0.930855
RMS Abs. Floor Acceleration (m/s2)
SA Friction Damper 0.924392 0.860956 0.910435 1.689969 0.948888
SA Stiffness Damper 0.847722 0.84289 0.906044 1.540652 0.889127
MR Damper 0.777966 1.096831 1.314699 1.165429 0.867645
SA F i ti D 8238 28 7665 5 4318 191 11394 66 8798 873
16
PeakControl Force (kN)
SA Friction Damper 8238.28 7665.5 4318.191 11394.66 8798.873
SA Stiffness Damper 7505.04 6440.726 3507.768 10165.83 7937.672
MR Damper 16535.46 18497.54 13848.27 14646.51 14301.21
17
ConclusionsThe comparative performances of semiactive dampers inbaseisolated building under the action of strongearthquakes acting bidirectionally have beenevaluated. The role of semiactively controlledstiffness/ friction dampers along with MR dampers inreducing the large base displacement in base isolatedreducing the large base displacement in baseisolatedbuilding are found suitable since they do not increasethe structural response like, top floor accelerations,base shear etc. to alarming level. MR dampers provedcomparatively better semiactive controlled dampers incomparatively better semiactive controlled dampers incomparison to friction or stiffness dampers.
17
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2) Spencer,Jr.,B.F.,andSain,M.K.,Controllingbuildings:anewfrontierinfeedback,SpecialIssueoftheIEEEControlSystemsMagazineonEmergingTechnology,17(6),
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