OSEA ASCE7-10 Most Common Errors in Seismic Design-04!14!15

8/16/2019 OSEA ASCE7-10 Most Common Errors in Seismic Design-04!14!15

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2015 OSEA Spring Conference – ASCE 7-10 Seismic - Common Errors 2

Acknowledgements

• Based Heail! on"

• #$e %ost Common Errors in Seismic

&esign'And How to Properl! Aoid

#$em• (CSEA )*+ Annual Con-erence

Proceedings

•B! #$omas . Heausler, PE, SE•Structural Engineer

•/ansas Cit!, %0


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Pre-ace

• 1isting o- common errors was

deeloped b! #om Heausler and Bob

Paullus during reiew o- ot$er

engineers2 work• Based 0n E3perience

• S$ould not be misconstrued as a

consensus document o- t$e ASCE 4Seismic Subcommittee

• %a! be used as a c$ecklist -or &esign

or Reiew


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Standards Coered

• ASCE 7-10

• IBC 2012

• AISC 360-10

• ASIC 341-10

• ACI 318-11 (including Chapter 21 and

Appendix !• "ther Standard#


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aorite #op #en Errors

• (o. +*" (eglecting Additional Re5uirements

-or C$ords, Collectors, 6 &iap$ragms

• (o. 7" 8mproper &istribution Base S$ear oer

Heig$t

• (o. 9" ailure to multipl! E b! *.4 -or AS&

design

• (o. 4" (eglect o- combining ort$ogonal

E--ects

• (o. :" R;


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aorite #op #en Errors

• (o. =" %odal Response Spectrum Anal!sis will

Capture All 8rregularities and be Conseratie

• (o. " (eglecting " (o or 8nade5uate Redundanc! in

S!stem

• (o. )" (o Continuous 1oad Pat$

• (o. +" ?8 &idn2t know 2all Had Eart$5uakes

Around Here


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Seismic &esign Categor! S&CD A

• ASCE 4;+* Section ++..+ ; %apped

Acceleration Parameters

• ASCE 4;+* Section ++.: ; SE8S%8C &ES8(

CA#E0R• ASCE 4;+* Section ++.4 ; &ES8(

REFG8RE%E(#S 0R SE8S%8C &ES8(

CA#E0R A

− Send to Section +. ; eneral Structural 8ntegrit!− reeboard Re5uirements -or RC 8< #anks"

Section +=.4.:.+.)


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Seismic &esign Categor! S&CD A

• ASCE 4;+* Section +. ; eneral Structural

8ntegrit!

− S$ould (ot Gse An! 0- #$e Proisions 0- C$apter +)

− 8nstead, Gse #$e eneral Structural 8ntegrit!

Proisions 0- Section +.

− eneral Structural 8ntegrit! Proisions Hae Some 1oads $ic$

%a! 0-ten Be Erroneousl! Gnaccounted or"

• #$e -orces re5uired include +I dead load, =I o- dead plus

lie load -or beam connections, and )*I o- wall weig$t -or

wall connections

• (on;Structural Components in Seismic &esign Categor! A

are e3empt -rom Seismic &esign re5uirements, as stated in

Section ++.4


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8mportance actor

• ASCE 7-10 Secti$n 11%&%1'a)le 1%&-2'

a)le 1%&-1

• IBC 2012 a)le 1604%&

− I*p$rtance +act$r I# Ba#ed ,p$n i#.

Categ$r/ And he A##$ciated ie Saet/'

aard And E##ential ature " he

Structure


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8mportance actor

• Chec. )$th ASCE 7 and IBC a)le#− A t/pical )uilding can #$*eti*e# e5$l5e int$

an Ie eual t$ 1%2& $r 1%& hen $ccupanc/ $r

u#e expand#%− Exa*ple#

• e5en relati5el/ #*all churche# ($ccupanc/

greater than 300!

• a )uilding here haard$u# *aterial# are #t$red

− +$r Building e#ign Ie 9 1%0' 1%2&' 1%&0


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8mportance actor

• $n-Structural C$*p$nent#− Ip 9 1%0' $r 1%& $nl/ ASCE 7-10 Secti$n 13%1%3

− Ip *a/ n$t eual Ie' and in #$*e in#tance# Ip

*a/ )e le## than Ie%


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Continuous 1oad Pat$

• ASCE 4;+* Section +).+.>

−


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Continuous 1oad Pat$

• ASCE 4;+* Section +).+.>

− 8n Addition #o #$e Speci-ics, #$e

Engineer 8s Re5uired #o Proide A

Continuous 1oad Pat$ or All 8nertialorces

− rom #$eir 0rigin #o #$e oundation

− Suc$ 1oad Pat$ S$all Con-orm #o #$e

Relatie Sti--ness And Strengt$ 0- #$eElements $ic$ E3ist 8n #$e Structure

• &e-ormational Compatibilit!


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Response %odi-ication actor" R

• ASCE 4;+* #able +).);+ and +=.;+, )

− #$e Response %odi-ication Coe--icient, R, 8s

Part 0- A Concept $ere An Elastic &esign

%a! Be Per-ormed− But it$ &ue Consideration 0- #$e

0erstrengt$ And &uctilit! 8n$erent 8n #$e

1ateral orce Resisting S!stem.


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Response %odi-ication actor" R

• #o Assure Reliabilit! 8n #$e 0erstrengt$

And &uctilit!, %an! Re5uirements Are

#riggered it$ Eac$ R actor •

?R #ables 1ist #$e &etailing Re5uirements#riggered

• #$e ?Strings Attac$ed #o A8SC R> Structures

And AC8 C$apter )+ Structures Can Be E3tremel!

Signi-icant


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0erstrengt$ actor" K*

• ASCE 4;+* #able +).);+

− Also in ASCE 4;+* #ables +=.;+, and +=.;)

• $en &iap$ragms Are le3ible

− Allowed #o Reduce K* actor B! *.=

− #$is Proision 8s 1isted 8n Small Print As

ootnote g And 8s 0-ten 0erlooked


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%odal Response Spectrum

Anal!sis #riggers

• ASCE 4;+* Section +).>

− #able +).>;+ ; HoriLontal 8rregularities

− #able +).>;) ;


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Anal!sis #riggers

• ASCE 4;+* Section +).> #able +).>;+

and #able +).>;)• #ables Re5uire Close Reiew #o 8nterpret #$e

#riggers.• #$e ASCE &esign uide Seismic 1oads" uide

#o #$e Seismic Proisions 0- ASCE 4;+* B!

inle! C$arne! Has A 1isting 0- #$e #riggers

8n A %ore Gser riendl! ormat


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0erstrengt$ actor, K*, #riggers

− ASCE 4;+* Section +). ; 1oad

Combinations wit$ K*

− ASCE 4;+* Section +).).=.) ; Cantileer

Columns

− ASCE 4;+* Section +).+*.).+ ; Collectors M

1ig$t rame, ood E3cepted

− ASCE 4;+* Section +).>.>.> ; Columns,

Beams Supporting &iscontinuous alls− ASCE 4;+* Section +).+>.:.= Pile Anc$orage

− A8SC w$ere R>

− AC8 C$apter )+, Appendi3 &, etc.


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0erstrengt$ actor, K*, #riggers

• K* 8s An Ampli-ication #o #$e orces

− or E3ample"

• 8n a steel braced -rame s!stem, in order -or t$e

diagonal brace to !ield and dissipate energ! in acontrolled and reliable manner, all ot$er portions

o- t$e load pat$ E.. Connections, bolts, welds,

gusset plates, anc$or bolts, columns and

collectorsD need to be stronger t$an t$e ma3imum

anticipated strengt$, or -orce, in t$e brace.#$ere-ore, omega Lero ampli-ication and load

combinations are speci-icall! triggered in t$e

sections mentioned aboe and in material

standards suc$ as A8SC and AC8.


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Redundanc! M R$o ND

• R$o 8s A actor #$at PenaliLes

Structures #$at &o (ot Hae

Redundanc!

• ASCE 4;+* Section +).>.− R$o O +.* or +.>

− R$o O +.* -or" S&C B, C, -or &ri-t

Calculations, p (on;structuralComponentsD orces, Collectors, K* 1oad

Combinations, and &iap$ragms


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1oad Combinations and

Allowable Stress &esign M *.4 E

• or Allowable Stress &esign AS&D 1oad

Combinations

• ASCE 4;+* Section +)..).>

• Section +)..) s$all be used in lieu o-

Sections ).>.) and )..+

− Eart$5uake orces Are At Strengt$ 1eel

So or #$e AS& Combinations, Gse *.4 Eor 1R& Gse +.* ED

− #$e *.4 E Applies #o p (on;structural

Component orcesD Also


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0rt$ogonal E--ects

• Eart$5uake orces S$all Be Calculated

or Eac$ 0- #$e #wo Primar!

0rt$ogonal &irections

− #o Consider #$e E--ects 0- Eart$5uakeorces At Some Angle 0t$er #$an #$ose

#wo &irections, ?0rt$ogonal E--ects %ust

Be Considered


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0rt$ogonal E--ects

• ASCE 4;+* Section +).=

− Re5uires #$at 8rregular Buildings 8n S&C C,

And Corner Columns 8n S&C &,E, Be

Considered it$ +**I 0- orces 8n 0ne&irections And >*I 8n 0t$er

− 8t S$ould Be (oted #$at 8EEE :7>

Electrical E5uipmentD Applies 0rt$ogonal

E--ects #o All Conditions, 8ncluding CornerAnc$or Bolts


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E--ectie Seismic eig$t

• ASCE 4;+* Section +).4.) de-ines t$e

E--ectie Seismic eig$t, .

− E3cept as mentioned below, lie load is not

included in t$e inertial -orce, $oweer t$eseismic -orce is later combined wit$ dead

and lie loads in t$e load combinations

• ASCE 4;+* Section +).4.) stipulates t$at

s$all include t$e -ollowing masses")=I o- Storage lie load, Partitions +*

ps-


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E--ectie Seismic eig$t

• ASCE 4;+* Section .>.)

− 8ndustrial 0perating eig$t M and

unbalanced conditionsD, )*I o- snow

>*ps-, and Roo- ardens.


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Period #

• ASCE 4;+* Section +).9.).+ $as comple3

met$ods and limits on calculating t$e

Period #.

− 8t 8s Acceptable #o Gse # O #a, orSimplicit!

− Appro3imate ormulas S$all (ot Be Gsed

or (on;building 8ndustrialD Structures,

ASCE 4;+* Section +=..


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&istribute Base S$ear oer Heig$t

• ASCE 4;+* Section +).9.>

− 0nce #$e Base S$ear,


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&istribute Base S$ear oer Heig$t


− 0nce #$e Base S$ear, 0- #$e Heig$t Aboe #$e Base, (ot

+) Heig$t 0r Center 0- rait!


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&istribute Base S$ear 0er

Heig$t ormula


− E5. +).9;+)D 3 O C3 <

− C3 O w3 $3k Sum wi $ik

− Spreads$eets are o-ten used to calculatet$e -orces at eac$ -loor leel

− A common mistake is to $ae errors wit$in

t$e spreads$eet logic andor calculate C3and t$en multipl! it b! total eig$tD orw3 weig$t at eac$ -loor. C3 s$ould be

multiplied b! t$e Base S$ear


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Anal!sis

• ASCE 4;+* Section +).7

− #$e purpose o- a %odal Response

Spectrum Anal!sis is (0# to re-ine t$e

magnitude o- t$e Base S$ear − Purpose 8S to more accuratel! per-orm t$e

-ollowing"

• &istributes Base S$ear 0er Heig$t

• HoriLontal #orsional E--ects• Hig$er %ode E--ects


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%odal Anal!sis

• ASCE 4;+* Section +).7..+

− Scaling 0- #$e Results 0- %odal Response

Spectrum Anal!sis 8s Re5uired And

Allowed.− Especiall! or Buildings, #$e Results 0-

#$e Response Spectrum S$ould Be


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%odal Anal!sis

• ASCE 4;+* Section +).7..+" Results

must be scaled to wit$in 9=I o- <

calculated b! E1 %et$od

− 8t is o-ten wise to c$eck !our so-twareresults wit$ a small regular structural

model w$ere results are predictable wit$

$and calculations

• Con-idence is gained to use t$e so-tware on alarge comple3 structural models.


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Accidental #orsion

• ASCE 4;+* Section +).9..)

− Accidental #orsion %ust Be Applied

− 8n Addition #o 8n$erent #orsion

− Re5uired #$is 8s #o Preent eak#orsional Resisting Arrangements As ell

As Account or Gne3pected &istribution 0-

1ie 1oad And Gne3pected Sti--ness 0-

Structural And (on;structural Elements− Proision Applies #o (on;building

Structures As ell As Buildings


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Accidental #orsion


− or #orsionall! 8rregular Buildings,

Ampli-ication 0- #$e Accidental #orsion

%a! Be Re5uired− ASCE 4;+* Section +).9..>

• See igure +).9;+ #orsional Ampli-ication

actor, A3

•


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Accidental #orsion


− ASCE 4;+* Section +).9..>

• $en C$ecking -or #!pe +a or +b #orsional

8rregularit!

− Gse #able +).+);+ to &etermine Ta

• #$e ollowing Recommendation 8s (ot

Currentl! in ASCE 4

− Recommendation rom Presenter, 0nl!

− 8 #$e Stor! &ri-ts At All 1ocations 0n A1eel Are 1ess #$an *.+=Ta to *.)*Ta, &o (ot

Consider A #orsional 8rregularit!


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Accidental #orsion

• E3ample" #orsion w


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&ri-t C$eck

• ASCE 4;+* Section +).+)

− Section +).9.: &ri-t &etermination

• ASCE 4;+* #able +).+);+ ; Allowable

&ri-t 1imits− Results -rom t$e elastic anal!sis must be

ampli-ied b! Cd to render actual e3pected

de-lections.

− Cd is a er! large alue, t!picall! a -actor o-

about > to =


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&ri-t C$eck

• ASCE 4;+* #able +).+);+ ; Allowable

&ri-t 1imits

− #$e dri-t is t$en diided b! 8e, because t$e

allowable dri-ts are organiLed into a tablew$ic$ considers Risk Categor!

− Be care-ul w$en using Allowable Stress

&esign load combinations

− &0 (0# appl! t$e *.4E to dri-t calculations


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&iap$ragm orces

• ASCE 4;+* Section +).+*.+.+

− orces At 1ower loor &iap$ragms %a! Be

Hig$er #$an #$ose Gsed or #$e 1ateral

orce Resisting S!stem− &ue to &iap$ragms #rans-erring 1oads

-rom 0ne


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&iap$ragm orces

• ASCE 4;+* Section E5 +).9;+)D 3OC3<

− #$is 8s &ue #o Hig$er %ode E--ects 8.E.

%odes Hig$er #$an #$e irst %odeD $ere

#$e 1ower loors %a! Be AcceleratingHig$er #$an Calculated 8n E5 +).9;+)D

− #$e &iap$ragm orce E5uation ASCE 4;+*

Section E5 +).+*;+D 8s Similar #o E5 +).9;

+)D, Howeer p3 %inimums 0- E5 +).+*;)D0-ten oern or #$e 1ower loors


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p (on;structural Components

C$apter +>

• ASCE 4;+* E5 +>.>.+D

− (on;structural components ma! also

e3perience $ig$er local accelerations due

to $ig$er mode e--ects as well asampli-ication o- t$e -orce wit$in t$e non;

structural element itsel-

− 8ndustrial structures o-ten -eature er!

large p -orces


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C$apter +>

• ASCE 4;+* E5 +>.>.+D

− 8t 8s Gnlikel! #$at #$e p orces 0n #wo

&i--erent loors ould 0ccur At #$e Same

Point 8n #ime− 0ne %et$od 0- Accounting or #$e p

orces 8n A Computer %odel 8s #o Run #wo

Conditions


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C$apter +>

− #o Run #wo Conditions"

• Run < 1oad Combinations it$ #$e eig$t 0-

#$e E5uipment 8ncluded 8n #$e Seismic eig$t

0- #$e loor And Base S$ear &istributed 0er

#$e Heig$t Per E5 +).9;+)D• Run p 0n Piece 0- E5uipment 0nl! #o


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C$apter +>

• ASCE 4;+* Section +=.> ; (on;Building

Structures Supported B! 0t$er

Structures

− $en t$e eig$t o- t$e Supported (on;Building Structure is 1ess t$an )=I o- t$e

#otal Structure %ass

• Gse C$apter +>

− $en (on;structural Components et .)


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1arge p (on;structural

Components C$apter +=

− $en (on;structural Components E3ceed

)=I 0- #otal Structure %ass

• or #$ese Hea! Components, A Computer

%odel Capturing #$e Sti--ness And &esign

Coe--icients 0- Bot$ #$e Component And #$ePrimar! Structure %ust Be Considered #oget$er

− %ust Appl! E #o p Combinations

− R$o Redundanc!D O +.*

− K*

&oes (ot Appl! #o p

1oad Combinations

• E3cept, K* &oes Appl! 8n AC8 Appendi3 &

Calculations


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all &esign

• all Panels %ade 0- Concrete And

Concrete %asonr!, C%G Hae

Per-ormed Poorl! 8n Past Eart$5uakes

• ASCE 4;+* Section +).++.+ ; allPanels

• ASCE 4;+* Section +).++.).+ ; all

Connections S$ould Be 8mplemented,As ell As AC8 Appendi3 & or

Anc$orage


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oundation #ies

• AC8 >+9;++ C$apter )+"

− #o Assure #$at #$e oundation S!stem

Acts As An 8ntegral Gnit

− Preents 0ne Column 0r all rom %oingAppreciabl! wit$ Respect to Anot$er

− Applies #o Pile Caps 8n S&C C, As ell As

&,E,, and Spread ootings -or S&C E and

− Can Possibl! Be 8ntegral it$ Slab or1ig$tl! 1oad Buildings Engineered %etal

BuildingsD


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Reduction o- oundation

0erturning

• ASCE 4;+* Section +).+>.

− Allows -or a reduction o- t$e bearing

pressures at t$e Soil;oundation 8nter-ace

− orces ma! be reduced b! )=I inrecognition t$at t$e -irst mode triangular

-orce distribution will likel! not occur

wit$out $ig$er mode e--ects occurring and

negating t$e direction o- t$e -irst mode• Results in reduced oerall oerturning moments


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8BC )*+) 0errides

− ASCE 4 is on a si3 !ear update c!cle and

8BC is on a t$ree !ear

− Also tec$nical c$anges to 8BC o-ten $ae

to be approed well be-ore t$e issue date• 8neitabl!, Coordination Between #$e #wo

Su--ers

• %aterial Standards 8ssues %ust Be Coordinated,

0-ten #$roug$ Errata, Supplements 0r 8BC

Publis$ed Amendments. 8t 8s Essential #oPeriodicall! C$eck or #$ese C$anges

• See Standards Suc$ As" A8SC, AC8, A8S8, AC,

Etc.


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ASCE 4;+* #H8R& PR8(#8(

− 8t 8s Recommended #$at #$e Gser %ake

Gse 0- #$e ASCE 4 E3panded Seismic

Commentar!

−

+>= Pages 0-


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ASCE 4;+* #H8R& PR8(#8(

− or #$ose #$at 0wn A irst And Second

Printing, ou %a! &ownload A U .pd-D ile

0- #$e Commentar! or ree rom #$e

ASCE ebsite

− #$is Commentar! as &eeloped B! #$e

(EHRPBSSC Proisions Gpdate

Committee and &escribes #$e Reasons or

#$e 8ndiidual Proisions 0- #$e ASCE 4

Standard


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Re-erences

• ASCE 4;+*, %inimum &esign 1oads -or

Buildings and 0t$er Structures, #$ird

Printing, American Societ! o- Ciil

Engineers, Reston,


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Re-erences

• AC8 >+9;)*++, American Concrete

Association, armington Hills, %8 9>>+

• ASCE C$arne! P$.&., P.E., inle! A."Seismic 1oads" uide to t$e Seismic

Proisions o- ASCE 4;+*, American

Societ! o- Ciil Engineers, Reston,


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OSEA ASCE7-10 Most Common Errors in Seismic Design-04!14!15

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