Stress Field Eval in CGDs using Pseudo Stat & Pseudo-Dyn Approaches (2013) - Paper (15)

8/12/2019 Stress Field Eval in CGDs using Pseudo Stat & Pseudo-Dyn Approaches (2013) - Paper (15)

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STRESS FIELD EVALUATION IN CONCRETE GRAVITY DAMS USING THE

PSEUDO-STATIC AND PSEUDO-DYNAMIC APPROACHES

Paulo Marcelo VIEIRA RIBEIRODoctorate Student, Universidade de Braslia UnB

Lineu Jos PEDROSOPro!essor, Universidade de Braslia UnB

Silvio "ALDAS"ivil En#ineer, "entrais Eltricas do $orte do Brasil % ELE&RO$OR&E

Bra'il

&raditionall(, concrete #ravit( da)s *ave +een desi#ned and anal('ed +( asi)li!ied rocedure, -*ic* does not consider t*e structural elasticit( and t*e !luid

co)ressi+ilit(.Pseudo%Static Met*od/0 So)e aut*ors *ave alread( !ound out t*att*e consideration o! t*ese asects can roduce si#ni!icant stresses in t*e da),indicatin# t*at t*e si)le rocedure )i#*t not +e aroriate !or t*e desi#n o! t*ist(e o! structure 12,340

A stud( conducted +( 124 indicates an alternative rocedure !or evaluation o! t*eseis)ic actions, incororatin# t*e e!!ects o! t*e elasticit( o! t*e structure and t*eco)ressi+ilit( o! t*e -ater0 It is a si)li!ied anal(tical rocedure, +ased on t*esectral resonse o! t*e structure0 Its alication consists in t*e calculation o! t*eseis)ic loadin#, -*ic* s*ould +e alied to t*e da) in a e5uivalent staticanal(sis0

In desi#n conditions -*ere t*e da) can +e treated as a ri#id +od( .eriod o!vi+ration is aro6i)atel( e5ual to 'ero/, t*e roosed )odel +( t*e Pseudo%Static)et*od is aroriate, and a constant distri+ution o! seis)ic accelerations alon#t*e da)7s *ei#*t can +e adoted, ne#lectin# relative )otion contri+ution0 &*is)et*od considers t*at t*e da) is rovided -it* t*e sa)e acceleration o! anin!initel( ri#id !oundation, and t*e ea8 #round acceleration roduces t*e lar#estseis)ic e!!ects on t*e structure0

9o-ever, t*ere are conditions -*ere t*e e!!ects o! t*e !le6i+ilit( o! t*e da)


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s*ould +e considered, and anal(sis o! t*e d(na)ic resonse o! t*e structure isneeded0 &*ere are reorts o! accidents -it* da)s t*at -ere desi#ned +( t*etraditional rocedure, -*ic* -ere su+)itted to seis)ic actions )uc* *i#*er t*ant*ose laid do-n +( t*e usual ri#id +od( rocedure 1240 &*e :o(na da), !or

e6a)le, -as desi#ned -it* a seis)ic coe!!icient o! ;0;?eart*5ua8e, occurred in India, -as a+le to roduce actions t*at e6ceeded t*edesi#n considerations0 As a result, )an( crac8s -ere !or)ed alon# t*e da)0

&*e structural !le6i+ilit( is o! !unda)ental i)ortance !or understandin# t*eactions roduced +( t*e eart*5ua8e0 A lar#e a)li!ication o! t*e #roundacceleration can occur -it* t*e consideration o! t*is e!!ect0 @i#0 2 and 3 illustratet*e total acceleration resonses roduced in a s(ste) o! 2 de#ree o! !reedo).o+tained +( nu)erical inte#ration, usin# a !ourt* order Run#e%:utta rocedure/,-*en su+ected to a s*ort ran#e o! t*e nort*%sout* co)onent o! t*e El "entro

eart*5ua8e % 2=; 1C40 &*e !irst s(ste) *as a eriod o! vi+ration e5ual to ;0;3s,-*ile t*e second s(ste) resents a eriod o! vi+ration e5ual to 2s0 &*e da)in#!or t*e t-o situations is e5ual to 30 It can +e o+served t*at in t*e !irst s(ste).@i#0 2/ t*e resonse aroac*es t*e #round acceleration0 &*us, t*is indicates ari#id +od( )otion0 &*e second s(ste) resents an a)li!ication o! t*eacceleration resonse, -it* resect to t*e eart*5ua8e roduced co)onent0 At acertain instant t*e total acceleration ac*ieved +( t*e s(ste) is t-ice t*e value o!t*e #round acceleration0

&*e +e*avior s*o-n in @i#0 2 reveals an i)ortant c*aracteristic o! t*eseis)ic desi#n sectra0 On t*is dia#ra) t*e sectral acceleration tends to )ove

closer to t*e ea8 #round acceleration as t*e eriod o! vi+ration o! t*e structuredecreases0 &*is indicates t*at t*e s(ste) ac5uires roerties si)ilar to t*ose o! ari#id +od( )otion, -it* t*e total acceleration resonse aro6i)atel( e5ual to t*e#round acceleration0 In t*ese cases t*e use o! Pseudo%Static )et*od isacceta+le0 Accordin# to 14 t*e use o! t*is rocedure is valid !or da)s -it*!unda)ental eriods o! vi+ration less t*an ;0;Cs0 &*us, t*e da) can +e treated asa ri#id +od(, -it* a constant coe!!icient e5ual to t*e #round roduced acceleration,distri+uted t*rou#*out its *ei#*t .so)eti)es called seis)ic coe!!icient )et*od/0Structural relative )otion is ne#lected on t*is t(e o! anal(sis0 &*e +e*aviors*o-n in @i#0 3 illustrates a d(na)ic a)li!ication o! t*e #round )otion0 In so)ecases t*e #ain reac*es ?


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&*e Pseudo%Static )et*od seis)ic actions are derived !ro) t*e *(ot*esiso! a ri#id +od( )ovin# to-ards an inco)ressi+le !luid0 &*us, t*e structural )assis treated -it* a uni!or) distri+ution o! acceleration, e5ual to t*e in!initel( ri#id

!oundation acceleration0 &*e seis)ic loadin# .distri+uted er unit o! *ei#*t/ to +ealied in an e5uivalent static anal(sis is co)osed o! t-o arts t*e inertia !orceand t*e *(drod(na)ic ressures0 &*e !irst one is #iven +( t*e roduct o! t*ecorresondin# )ass distri+ution in t*e anal('ed section -it* t*e desi#nesta+lis*ed ri#id +od( acceleration0 &*e *(drod(na)ic ressure distri+ution is+ased on studies develoed +( 14, andreresents t*e inertial e!!ects o! t*e reservoir alon# t*e !luid%structure inter!ace0

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Stress Field Eval in CGDs using Pseudo Stat & Pseudo-Dyn Approaches (2013) - Paper (15)