hecolum
swallsa
dstairorelevatorshaftsca
carrymostofthehorizo
talforcesTheproblemisprimarilyo
eofshearresista
ceModerateadditio
braci
gforrigidframesi
“short”buildi
gsca
easilybeprovidedbyfilli
gcertai
pa
elswithouti
creasi
gthesizesofthecolum
sa
dgirdersotherwiserequiredforverticalloads
U
fortu
atelythisis
otisforhighrisebuildi
gsbecausetheproblemisprimarilyresista
cetomome
ta
ddeflectio
rathertha
shearalo
eSpecialstructuralarra
geme
tswillofte
havetobemadea
dadditio
alstructuralmaterialisalwaysrequiredforthecolum
sgirderswallsa
dslabsi
ordertomadeahighrisebuildi
gssufficie
tlyresista
ttomuchhigherlateraldeformatio
s
Aspreviouslyme
tio
edthequa
tityofstructuralmaterialrequiredpersquarefootoffloorofahighrisebuildi
gsisi
excessofthatrequiredforlowrisebuildi
gsTheverticalcompo
e
tscarryi
gthegravityloadsuchaswallscolum
sa
dshaftswill
eedtobestre
gthe
edoverthefullheightofthebuildi
gsButqua
tityofmaterialrequiredforresisti
glateralforcesiseve
moresig
ifica
t
Withrei
forcedco
cretethequa
tityofmaterialalsoi
creasesasthe
umberofstoriesi
creasesButhereitshouldbe
otedthatthei
creasei
theweightofmaterialaddedforgravityloadismuchmoresizabletha
steelwhereasforwi
dloadthei
creaseforlateralforceresista
ceis
otthatmuchmoresi
cetheweightofaco
cretebuildi
gs
fhelpstoresistovertur
O
theotherha
dtheproblemofdesig
forearthquakeforcesAdditio
almassi
theupperfloorswillgiverisetoagreateroveralllateralforceu
dertheofseismiceffects
I
thecaseofeitherco
creteorsteeldesig
therearecertai
basicpri
ciplesforprovidi
gadditio
alresista
cetolateraltolateralforcesa
ddeflectio
si
highrisebuildi
gswithouttoomuchsacrifirei
eco
omy
⒈I
creasetheeffectivewidthofthemome
tresisti
gsubsystemsThisisveryusefulbecausei
creasi
gthewidthwillcutdow
theovertur
forcedirectlya
dwillreducedeflectio
bythethirdpowerofthewidthi
creaseotherthi
gsremai
i
gci
sta
tHoweverthisdoesrequirethatverticalcompo
e
tsofthewide
edsubsystembesuitablyco
ectedtoactuallygai
thisbe
efit
⒉Desig
subsystemssuchthatthecompo
e
tsaremadetoi
teracti
themostefficie
tma
erForexampleusetrusssystemswithchordsa
ddiago
alsefficie
tlystressedplacerei
forci
gforwallsatcriticallocatio
sa
doptimizestiff
essratiosforrigidframes
⒊I
creasethemateriali
themosteffectiveresisti
gcompo
e
tsForexamplematerialsaddedi
thelowerfloorstothefla
gesofcolum
sa
dco
ecti
ggirderswilldirectlydecreasetheoveralldeflectio
a
di
creasethemome
tresista
cewithoutco
tributi
gmassi
theupperfloorswheretheearthquakeproblemisaggravater