-z/z- v;2..4, - concrete
TRANSCRIPT
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A 1R!C TUIA L E I I C I I I 'E R I i G
!TIUCTURAN MECX'NICS
cRADlAtE STltE{t ttsEttct xoloB?
-z/z- v;2..4,/t- r, i
Unlv€rrity ot c!1if or!i.Delaltrert of CIvi'I tn8thecilns
aerk]. y, Caltf.rda
EIIAVIOR OF A CO!:TIIiUOUS INESTNiSSED
COIiCREIE SL1.E ''ITI'
DRO! P4TAL6
Rob€r! J. Oal€llo
l. ri4. Mabta
Fqr.I s.ieer€! 19 57 N". 30?
la3r.E oF coltEms
LIS! OF FrGUR!6 . , . , . . . . . , . . . . . , . . . . . . . . t tusT 0t ? i lcrocl l t f i s , . . . . . . , , , . . . . . . . , . . , . . . . , , . . . . t t l
AESTFrCf. . . . . . . . . . . . . . . . . . . . . . . . . . . . . l i
I . INIRO'TJCIIoI . . . , . . . . . . . . . . , . . . . . . . , . . . . , . , . . . . , . . 1l , Goala ard Ecolo. i , , , i , , . . . . . . ! . . . . . . . . . . . . . .12. Aclno{ l€dgenebtr . . . . . . . . . . , . . . . . . . . . , . . . . . , .2
IL @mItEmAL pROci$. . . . . - - - . . . . . . . . . , . . . . . . . . . - ,t . Tesi specloen.. . . . . . . . . . . . . . . . . . . . , . . . . . . . . .J2. labrtcEl lor . . . . . , . . . . . . . . . . . . . . . . . . - . . . . . . . .4) . Uai€r la l . , . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . ,54. uothod ol l,o4dlng . . . . . . . . . . , , . . . . . . . . . . . . . . .55 . In6tlu€ntat1.r . . . . . . . , . . . . , , , . . . . . . . . . , . . , . 6
l l l . IHFpRETTCAL SI0DIES.. . . - . . . . . , , . . . . . . . . . . . . . . . .?l . Ela. t lc a8l tst ! . . . . . . . . . . . . . . . . . . . . . , . . . . . .72. s l i lc t€ Losar aE:,yal . . . . . . r . . . . . , . , . . . . . . . .6
tv. EXPEiIMENTAL R-oSIJITS!. . . . . . . , , . . , . . . . . . , . . . . . . .9f . roedlnS., , , . . r . . . . . . . . . . . . . . . . . . . . . . , . , , . , . ,92. Stralr 0a6€s., . . . . . . . . . . . . . . . , , , . . . . . . . . . . . f tf - Del lect lo!6. . . . . . . , , . . . . . . . . . . . . , , , , . . . . . . .114. Reoct lotr . . . . . . . . . . , . . , . . . . . . . . . . . . - . . . . . . . .1,
v. sutr4r,{AlY AlrD coNclJsrolre. . . . . . . . . . . . . , . . . . . . . . . . .11
I IGUBES.. . . . . . . . . . . . . , . . . . . . . , . . . . . . . . . . , . . . , . . . . . .16
; tcToeRAPHS.. . . . . , . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . t4
ct lc l j tATroNs.. . . . . . . . . . . . . . . . , . . . . . , . . . . . . , . . . . . . . .4)
qe! !E ElsilE&l
!I6u!6 lr
llau!€ 5t
l lgu! .61
Flgur. U
!14n end Ol€vsilon oi slab shdlrAsieel lrla.8€d€nt
Deta1l of Sup9olt AbBorbly
fyllcel Catlle llofIle
typl@l StF..-Sir'sIo CUF€ lor Conclot.
lae-c@p!e.!lee s!!€rgih Felatlo@btp
TY!1ceI st!...-9traln Curvo fo}!reBi!e6sIrg S!e€l
Locatlon of Oe8.3
untlotu lraal-D.1loct10n culv€ fo!
Doffecteil gb.pe. lo! unlloro lpail
Deflect€ar shale. tor unlton Loed
Measuled R€act10n.
FLau!. r2er UeasuEd R.eclLo4E erd calculat.dvalu€a
r18ur6 1rr Load Dls!.1butlo!
tlg\r!€ 14: Craci Ittlem on BoitoD Suface
FlAu!€ l5r Crack Pattort on Io! surraoeat FatlurE
ltsT oF PitoTocilqls
: roto€raPh t : F.ro3 and steel ArraneeDpot
slab tn Place o. leCestels
Siab rith loadlbts l!a66 Just
lrchoraee lnd ot rroker Tendor
center sutrloli After Fellure
lEf,"ltAql
l't sl..ttc b6havlor .nd ultlnate Btrs|gth o! .
aontliuou. corcEt. !l.b pE.t!e.ae<l ln tE dhotiotr rith
rboD p.rl.t. tffr ftp.gtlgatad. IE .t.b r€ lupFrt d at
nln. point!, dlmrlrtidg . llat .labi rn.tr€sdlhg eor a.-
@plIrh.d b'y @$E o! sbond.d po.t-t.ntlon4d crblet. It
r.. lo.dlrr Etlolrrly by ea. ol .tr Fs!3uE in ptatic
b!g.. ErFdicnt.f raber fo! d.fl..ttoB .trd Eactlor h:i
6dp.ied f,lth th.ontlca! v.lE. obt.ltEd by .pttodD.t
th.orL. e.d b pF.ent d..lgt Eth..L. Ob..wt<l ullil@tc
.t!.!ctn d. cdD.Ed ro th.t obtatn d by tt!€ pl..tlc hiog.
th.ory lb cohj&ctto! d,th th. lpDrdls.t. b.d iethod a
.ppu.d to pre.tl!.!ed ila!..
I. INTI{ODUCTION
1. qs& gg. lcrrstoat-tenalored conclete ftoo! 31abe ale becmihg
incleashgly popular ln ncw conattuctron. They ofler th.
a<tuantageE of thinr cracL-free E.ctiona vhich are 6tong,
ecohhical, and adthetically plesing. ll4evet, becau6e
of the 6tatically ind€tenrnant natuE of the 51ab6 dd the
edded c@plicatloE of pe8tre$lngr n@t 6l-ab de6igns are
trased oh applotinat. oalyse6.
Tltough Buch Blab3 hav. pertotud @!1 in sedrce,
there ae only e fee telta shich corleLate the acnrat rith
predrted 8!ab b.havi,6. tn !956, l-in, Scordelts, atd
?ister,r Eported oh test6 of . pE.tessed flat slab sup-
Dorted at four coher.. ttte.. te5t. shored that coftct
€lestrc and yield lihe theories for 61ab eav. good indrca-
tions of the cracking ehd ultiMte roa.Is respectively. rn
195r, Lia, Scordelis' and ay' d.vrtolEd . B6t-enpelica1
lelationdhi! ror th. 6ll@abl,e Ehea! .t!ea5 .rosd col\lm
supports of p&stfeEsed 6labs. L!n, scordet is, ed I taya'
anelyzed dd tested a 31ab aupported on nahe colmN to in-
vestigate the .ffect! of .ontlnulty. ttreEe test8 BhoEd
cLo€e correlation b€ta.n e16!!ic ttEoryr bea method, {nd
the actu6! behavlor oE tl€ rta!. 1. l9drr Flank Lu of the
$riversity of Canterbuly, Cristchurch, New z€alahd, condEted
2.
extensive tests on a 9-paDel post-tensioned slab. raft of
the reguLta eas described in a g.aduate 6tudent report at
U. c-, s.lkeley.s tlese tests again 6ho@d closc agEernt
of apploximate and co!rect eta8tic analyses rith the elEb
Itre curtent inE6ttgation 13 closely pattetual after
the Lint ScordeLis, Itaya tests. The slab is of the !.ne 6ize,
cohfiguation, and tendon affange.Ent. fhe hajo! difference
ls tn€ inclsaon of dtup panek over tlE colls suplorts. In
addition, the contltbution of the non-prestressed reihfo.ce-
ient over the suppolt. to the ultiEte Et.e!€th of the 31ab
rill !e .on6irieEd. the Flters fee! that such e iDve.tlga-
tion ril! be usetul beca8e designer8 dle beginning to se
drp panels to i4pFre the .tlength and behavro. of long-spd
lhi8 inv4tigstlon hd s.veral objectiveB. The ft.st
ia to d€temine ii the b.d @thod is applicable to 61ab. rith
ibop paEI.. since the ultimat. loa<t i€ a mportant <lestgn
consideratiotr, a Eecond goal is to det€rune how dlop DaneL6
alfect the failue node of the 51ab, Finally, the Fiter6
rish to gathe! sufficient data 60 that trtlle ihvectigatots
rar c@pare other aDpro*iMte o. exact method6 of d6!ysi3
with the actual slab hehdior-
2. 4eEeylg4sgrs$gIlIe .xpe.i@ntaL Progta 16. coAdet€d at the
strutu!5l Resealch knolatoly of the Univedlty of
califonia's Ri.hiohd Field Station, fiE Drogrd ras
6upFolted by iaculty 3nd studeht research glants tr@ the
DiviEion of Strctu.ar lbgine€ling end Stnctqal ltechantcs.
the Bite.6 ale indebted to oeolge sayLe! and Luis Tlescony
for their advice end help itr coturete pl&efunt, curing dil
ihstru€ntation fespectively. tle are thanktll !d Elvood
Bfomr! help in the initia! dtages of the expelinentBl vork.
tle alc aLao indcbted to Roy Stephen ard the 6ta!l of th€
stnrctoral Research kboratory fd 6dv1c. and aid. tle aE
alao thaDkful !o! the guldence Fovided by ;lote68or€ T. Y.
Lin, 14. S, !61ivka, dd A. C. Sco!de!i!.
11. EX(.]RI}ENIA! IROGR \ll
r. 1:!9 gtegisgs
Itre teat specien is ilesrgned to slmurat. 4 ap-
plorihat€Ly one-third sca'l€ f.de1 of a f@r bay lloof sy8t.i.
The ove!-all aize i6 fifteen feet by litteen feet. The slab
is suppo.ted at nane pointa fith s aeven-foot 6pe betEeh
the canteE ot suptorts- It. slab ;s thtee inch6 tbick dd
the drop !ane15 have a thicknesB of three addttlonal in hea.
fiE come! drop panels eere eLinicted to supufy fo@ng
dd consr4ction. (Se€ Figse 1) slnce ttley ale not in aeas
of clitical mo(ent or shearr thei! ab.ence should have littl.
eflect on the beh.vior. Th. slab rag post-tansloned by a
total of trenty-four l-in.h di3@tef tendd6 rith paper-.over
spaceil at fifteen inclEa center to cehte!. At the start of,
testlhg each tendon had a forc. of about 7750 posd3. TAe
teEdoD profile i3 sh6i in Fig@ 5. ftre drop-p4el6 contaln
4.
non-plesttessed letnforcenent in the fom o! +-inch di@te!
Ndefofred ba!s. t\. purlose of thi,s reinfolce@nt i6 to in-
cloade the €hear and honent eapacittr of the panels. A steeL
plete sith a bearing area of 3ix inches by 5ix inche6 {s
Eed at each slpport. A locke. and roller Erarrg4ent p€nitg
the neceesBry .otations and holizodta! nov€@nte so that no
feetraints r4l1 b€ intsduced at the suDporrs. (see rigGe 2.)
the cente! aupport pehits lotations about tro de6 but no
hodzdtal m@Ent.
the slatr ras foded and poued at gbuit leve1.
the lost-tensioning tendons and non-Dfestresed reinf orc@nt
@r. pleciaely held ln position by chails and sire.. The con-
crete tas d.Iive*d by ready-dx truck fsn a loce! supplier.
cylhderd and fl€$r. speci.hens were frade ^t
the tine of
c63ting. lle slab snd con..ol spciheG reE cuFd for r1
days under ret bufld! and plastic 6heeter and then teft to
dir-dry util te6ting. At the age of la daya the sleb Es!
pqt-tendioned 5o thAt teDdona were stressed to 17O l6i. At
2! days the p!est!€6s ras clEcked and set at 155 kgl for s1!
tendos. At 22 4aya trr4 €t.b 'as
lifted out of the fotu by
attaching cabLeg to eye-bolis rhich Ere scEsed into nuts
cast into the slab at the auplorts. The slab {as teEloraltly
set alo.g-3ide its oliginal positlon vhiL the fona FeE
r€moved and 18-in.h dtsete! by 56-ihch high corclere cyLinders
EE p66itioheil to act $ pedestals. The supprts 'eE
then
set on thes4 ledestals and 6et to glade with the ue of d
€ngtneelt8 tevel to Blnutate the otiginal support elevatiohs
fo! the 9 support points, At 26 dEys the slab was ri-fted
and s€t on the 5ulport8. The .lab conerE culled up uder
it8 o@ rel,ght, plobably dE to the eccentric effects of the
non-concordant cab14. lilhetr the relght ot the ai! bag6 sd
testinE fre wag sdded on top of the 61ab, the suppolt points
Tne cosc!.te dix sa. d.signed to produc€ a coo-
plesslve strengtb ot 5,000 p8i at 14 d.ys, the abticipated
age of testihg. Il|e nix contsiEd 10.25 sack6 of type I1
c@nt. Ille eater-cccot latio,a! 5.4 gak. De! sacL.
frre eggEgat constuted of lleaEanton dand sd glsvel hding
a me*tna .it€ o! 3/8 inche!. latch proporti.c tty Fight
t'ased on BAturated .rtace dry condttloE rere: €te., o.r4i
c@nt, 1.ooi sand, L.55: gravel, 1.28. lbe fi.enels uoillJlc
of the rand,a. 2.95, gravel, 5.42. ttE sl@p ras appro*i-
mately 1 inch and conclete place@nt too& appro*iGtely I
hou!. An admi*tuft. rorzolar ar sa8 added ln the arcunt of
o.20 !b. pe! aack of cenent. Contlo! epeci@M eeE cued
ih the sde m6nne! a6 the .tab. Three 6- by 12- tnch t4t
cylinde.s rere test.d at 7, !4, and 28 &y6. $ro 6-teh by
6-inch fles.al test specihene were tested by thild point
loaiting oo en lA-inch Ep.n at J2 days to detehdne ttre m6du1@
of dpture. me s@cant (odulus of el@tlcltt ras detemined
fror the avelage of tto .yLlnderB tested at !4 day6. lhe
iesults of these testa afe rdoh rn t6ble 1.
TAILE I
The p@t-t.$tonlnS tendoB had a noduluo of e!es-
ticity ot 29.7 x 106 psi. tne stess strain itiagro i. in
Figui. 7. l1l. non-prestre.sed reinfolc.nent had a modu!.s
of.lasticity ot 29.0 x 106 psi $d a yicl.l stength of
4. U9!!99 € rpadiig
R4felenc.r 1 and 3 lepolted €ati.factory re6ult8
using d ai! b.g ple8siEg .gainst a reactton frde to load
the sleb. Thls rethod raE used in the present investigatiob
siee it qa8 quite conwdient to tie the &actioh frft to the
lEavy anchor floor slab at the stnctlra1 R.6earch laboratory.
Air pr6suE wq€ me@l@d by the ue of a rat€r banonet.r &d
a bourdon gage, ldth thi6 arrdgeRent the plessule could be
rea3u@d to tlE neaEat 5 plf .
5. Inltruentatlon
It4 t6 the sydetly of the slab, electrical strain
gag€s were plac€d on the top and botton V8 of tl'e 51ab 1n
the ardrgdeht sh(m in Idgu€ a. strains in the tendoE
were to be d€temined fron the electrical at.ain gages placed
on tb.n near ttE dchor€ge en<I6. Six typlcal gafi.6 EE
28 d. 53
conpEssive StEngth (Fi) 5? 20 6720 7975
odulus of Ruptule
rr.odulu3 of ELsticity
chos€n for these seasEenentai h@evei, the gages failed to
fBction on th.ee of th€s€. ttle 6age8 ve.e elaced o. th.
t.ndon. eftef the llab s* caat: a.cess to th.n r.s Fovidcd
by block-outs. Slnce the.. bLock-out3 sre 6nall and located
at the ferth€at poift from the inatM.nted qu.drst, thei.
.ffect on the 31ab behavlor end data ras assqeil to b. n.g-
lte suppolt ftactiona weE easureil by pEssure
mete!8. aach pE6sure @ter consisted of 6-inch dieeler by
J/4-lnch rteer platea -ith
e 1/r6-incn oiL tih batreen them.
ltle pe63uE df th. oil tilo ,s deeduEd by a 6tandad pRs-
.ue gag. and the gages re!. caLiblated prao! to 8.. fh.
cente! aupport lequi.ed thlee s@h @tef6 because of thc
liFited lange of th. awail.bLe plessur gage6.
1II. Ti{IURITICAL STUDIES
r. gu4:9 44slx95llE elestic anBlysts {a6 based on the uea netnoa.4
Thi! e.thod consirt. of cobsi&ling the entile ridth of the
.leb a. e beo lupported on coniinuou tqlife-sdgd i! on.
directlon rhen the total noment is anal,yzed iE the perpeh-
dicular dtrection, The sual design cllterlon lor !ost-
ten€ion.d s1ab6 is based on al1@1rg no tenslLe lorce in the
concfete. sased on a to!.. of 7750 lb8. in each tendonr E
de3ig! load fo! ttl1a sLab vas 112 p!f. u6hg the see effec-
tive tendon force and a noduhs ot ruptEe o! 455 psi, the
load at vdich ctacLlrui stalted at the top of
port llhe ra6 conputed to he tt1 p3t.
a.
ltc deflection .t the center of a bay say also be
approxihated b'y the q€ ot the be4 @thod. The proc$6 con-
sist6 ot guperinposing the deflections of a 6ea acrcss the
collm suppolts and a beai in the opposite dilection consisting
of a one-foot strl! ni.lway bettreen the co1un6. By this nethod
the deflection was catcuLated to b@ 996 VE. ntLele { is the
unifonly distributed toad ltr p8f and E is the moduhs of
elasticity of concrete in D31, snd the deflectioh is in inches,
Ehe reactionE were also detelnined by use of the
bea method. ltre reactioN, expesded a6 a palt ot the total
load on the a1ab, l,l, aE 0.435 It fo! the cent€r supportr O.ll2 W
for the 6i.de suplprt6 etrd 0.029 W for the coha! supports.
2. ultinate Led 4lguglqBased on the bed method and the plastic hinga
theory, the ultinate }o.d wa5 c.lculated to be 5oo p3f.
According to this an.lysi8, hinges sholld foa over the cen-
ter suppolt tl@ ahd 2.45 f.et frm the side support lines.
n\is toad ras based on the fotlokj.ng a6suptioN: a recte-
gula! codclete stlesg btock at failuie' uttiMt. concrcte
strain of 0.OO34, @rimM tendon stress of 2oO k6i at failure.
fliLe carcul.ted leactions near the ultt@te load vele 0.344 W,
o.l1a w, ahd 0.056 \l at thc cente!, 6ide, and corner support6
respectively. An snalysis of the uLtinate ehea! capacity of
the slab indicated th€t rhear lellure should not be a probleb
at Loads belw 650 paf.
IV. EXIERI}IENTAL RESIJLIS
r. I4eggsMea.uraent. ere filst taken in apploximately
50 psf incEmcnts up to a load ot 20o psf.
then reteased fron th. air bag8. Next the Load was increase(l
in loo Ff incemertd to e load of loo p3f, at rhich poiht it
e$ incrcas.il by 50 plf incre@n$ unti! the fir8t vidible
cfac|ing at the bott@ of tbe 6lab occued st 434 paf. Lad
pas increased to 5OO psf wh.n noBt of the bottoh cia.ks de-
veloped. llE plessuE ,aa then &leaaed until the clEcks
alnost closed at !45 Ff- lbed eee then increas.d unti! the
alab f,ailed in fresft et 5Ao psf. Ihe Blab ras stiu abte
to s$tain ad<lttional road until lt faile.t in conbine<l lhed
tnd ftexure at 612 psf. tte c.ack psttems on the bottd
.nd top of the Blab .ppear in ligaes t4 and L5 reapectivel,y.
I. Figue 14, the nhbers i,Ddicate the d€q@nce ih shich the
crack6 .ppeared at the bottd. fhis clack pattem is aLmost
the sl@ as that predicred by the !1ti@r. fo6d &alysls.
r11e 6ldb lailue ,a itrtelesting i. 66ny ray.. fde
ftatefr half of the 31ab (See Figurc 14.) exhibited the ndt
.eve* clacking and deflectioru. ltle odinu d.flection
@ssufed at the north-south c.ack on that half of the stab
wa. about r l/4 inche.. Altef the 61ab t6ir,ed dd the live
load ra. ftleaaed, thi8 defl,ection rd leduc.d to about 1 1/4
inche8. Tni. lBylnetrical failuE mig-ht have been th. !e-
.ult of a slight leak obsened in the air bag oh the nolth-
lo,
A second interesting th€ faituE o!
a button on the jacking end of th. thi.d tendon fron the
northem €dge of th. 8lab. ttlen the tendon {ailed et e load
ol app.o*i@tely 600 p3lt the dchorag. €nd of the tendon
p|erced a 3/4 inch 6heet of plr{ood 6d dld not stop stil
appfoximately 2 feet of the tendon qss plojecting out of ths
.onclete. An exanibation of the bltton indicated a clp-cone
typ€ failure ,lth the tip of the cone about I/4 button .adi@
within the button. Srch a fractu. indicates teilule ra8
csused by a strecs concentration arornd the buttm .athe!
than a cooplet. te$lt. failse of, the tendon itself. SEh
. failuE not only defionstratea the asfety hazltds ihvolved
in the testin8 of unbonded tendona, it ako indlcateE a po-
tential .ouEe of @.loess ih th€ type of tehdotu ued i!
A cdrbined shear and flesre failu@ aroed ttE
center support vas the source 6f the dltimate faiL!!€ of
the slab. Crack3 occuned on the top of the 61ab at a to-
cEtion approxiRately above the edge of the dloP p6nel, IhF
.facLs weft at an angre of about 25o flm tlE horizont3l-
fhe pledicted failule toad ea! 500 p8fi howevell
the slab actually failed in fLesre at 58o psf. tlE brok€n
tendon indicated the hdihs tendon stE66 may have excee&d
the asa@d val@ ot 2OO krt. If, re asswe a narin@ tendon
ltlees of 250 kBi at failute, the .alculated ultimte load
bec6de. 562 p3f. thi6 value is rithin i l/2 per cent of
the t€st value. such a deviAtion iE well rithln the inac-
cula.ies inherent in er?erirentat @!kt the asseption of .
rectangular stress block for conccte, and the bee hethod
T.blc 11 codpa.es the b€travio. of th€ present slat
with that ol the slab in Rcference 3, the only slgnificant
rodlfication in the present 31ab i. the sddition of drcp
pdel. and the slightly hiEh.. tendoh stre.s (about 15 pe!
cent) in both tbe .lestic and uLtinat. rdge. 11t13 table
6ho€ thet in this case, drop panels incea6ed the over-all
average depth by abolt 15 rer centr rhe.eas '
the cleckiEg
and ultinate loads @re incleased .bout 25 and 40 per cent
Are rcst unfortsate occuEsce durtne thi,o studt
ras the l@s of strain gage data. I'tE aut@atic recoldihg
apparatus which the Mitels pLaNed to use .ould not b€ !e-
paired in ti@ for the test. At the cdpletlon of the testingr
the alteoste, ndual recording devtce va6 lomd to be MI-
functioning, and e a !esu!t, al! ltrain neasuErents ree
eSSE
Up to a load of 400 p8f, the cente! defLection!
varied linearlr {ith the loed. (Se€ Fieule 9.) secaue ot
thid linea. vadatlon it 1. eady to compaE ttE cglculated
and ne6sued deflectioN at a given load of !00 D5!. U3ltrg
the seaeuEd vaL@ o! E ih the explessim €or the d.flectld
givcs 0.026 lnch€a et the center of the bey. !t€ Eeesulsd
vale ea€ 0.042 inches. thi. difference reflects the
t3.
epp.oxi@te natlre of the lem dethod, Due to the lalgs nu-
be! of ucontroued factol8 in a design si.tuation, B@h an
er!o. i3 acceptable i! the designer Ealizes the qualitative
nature of th. eatihate.
The deflected shap€s lot valious cross-ssctions at
loo .hd 200 Ff are shom in FiSuEs Io and U. Itese .hape6
may plove to be of se for cooparison fith va1ue6 foad by
& exact eLastlc anely8ls.
lte measuled reaction€ at different supports fo!
vdiou load. are 6h(m in ?igue 12. rtese valnea tend lo
cd€ cloae to the pr€dicted values in th4 elastic range. Ihe
valiationE nay be due to E.me slleht hsymetly in the Bleci-
nen. Dre to the plastic load ledtutribtrtion, the reactio@
in the ulti@te rane.€ tended to be E@h clo6e! to the D!e-
dicted value6. (See Flgu.. ia.)
V. SII}OIARY AND CO'I:LUSIONS
ltE behgvior of . 15 x I5 foot pEatressed concEte
Blab, 5 ihches thi.L, auppolted at 9 pointG wlth <irop panel!
a additlonal 5 lnch€B thick aldnd the suppolte w$ studicd
exp.rinentally and by appro*imte theoretical anrlysia. Lait-
ing conditions Fere tlEt of a aifofrLy distlibuted load der
lbing the bee @thod of analysis the de6igr live
load ba3ed on no tetuion in the con.ete ras cmputed t6 !.
1L2 psf. Itte liv€ road fo! cracking based or a Dodulu of
L4.
tupture for conc&te of 453 psi, ra6 557 psf. Ite ulti@te
live load based on a maxinm tendon stlea6 of 200 k6i was
500 p8f. tlE .ctul hehavio. proved to tE id.at fo. prac-
tical applications o! thia typ€ of slab. Due to the lo6s o!
strain gage data, ther ra8 no ray of detemining when the
fi!6t crack occuried at the top 6ulfacet Howqver, clecking
at the bottm sulface ,aB filet ob6eded at a llve 1o.d of
4t4 p3f. fhe lBinu deflectioh at tbat tine las about 0.40
inctEs. Itle slab failed in flsre at 580 Fs! and cohplete
failua of c@bined shear anal fl€$r. oc.ured at . live load
of 612 paf. Ju6t p!io. to cmplete failure, the maxind de-
flsction ras r r/4 inches.
saaed on th16 6tudy the lo11owing con.l@ions se!.
1. Ite bean nethod of aEtysls may !e used to
.stisfactorily pEdi.t the elastic ed ultiMte behavio. o!
a po6t-t€n6io@d cohc.ete .Iab with drop panel€.
2. Fo! plactical applicatioE, mEh Fo4 cignifi-
cance ahould b€ given to the ultimte load thah to the c!!cL-
irlg Io.d since the 31ab c6n sBtain nEh add:itioMl Ioad md
dcllectlon betueen cracking and cNplete faiLufe.
t. Codpaling the bebavior o! the plesent alab *lth
thst d4cribed ln REfelence 5, the only lignific€ht modtfica-
tion b€ing the addition of drop panel6, the clacLing sd
ultiEate load cBllyi,Dg capacity of the .!ab wele iEcleased
REPRENCES
l. ]'in, T- Y.t s€ordelie, A. c., and fioter, k. S.,nstlenqth of a ConcEte slab Plestlessed in t\.oDi lect Ion. ' r , ACI Jotmal, vol .23, No.3, Septe(berL956, Dp. 24I-255.
2, I lnr t . Y. , scord. l is , A. C., sd Vlyr H. R,, ' 'Sh.dingStEngth of FeatEased Concr.t. L!!t Stabarr, ACIJomalr vol. 50, no. 4, octobe. 1950, pp. 4a5-506.
, . l tn, I . Y. , Scord. I is , A. c. , .nd l t .y6, R., "B€haviorof a Conti.neu s!.ab !E!t!er!ed in T$o D1!actionr'!.AcI JorEt, vo!. 31, No. 6, tEceDber L9s9, pD- 44L459.
4. Lin, T. Y., "De61gn o! Eestle.Bed coDcletc stactuEs',Johr wiley & Sor., Ner York! 1965, Dp. 579-163.
5. G\rptE, B. S., rtAn Analysis ot 6 conttnuoB Flat Stat)Ple6tles€ed tn two DhectionB". Craduate Student Re6earchreport, Dlv. of S. E- S. M., Uiir€4lty of Califonia,lerk ley, 1966.
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