performance of pc slab

8/3/2019 Performance of PC Slab

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PERFORMANCE OF PRECASTPRESTRESSED HOLLOW CORESLAB WITH COMPOSITECONCRETE TOPPINGNorman L. ScottPresidentThe Consulting Engineers Group, Inc.Glenview, Illinois

This load test of a machine-made hollow-core slabwith composite topping verified a number ofaccepted industry design and fabrication practices,specifically the following:

1. Impact test hammer data taken on the sideof the member provided an accurate assessmentof concrete strength as determined by uncrackeddeflection behavior and ultimate moment capacity.

2. The observed ultimate moment was about10 percent greater than calculations based onEq.(18-3) in ACI 318-71 but nearly identical tocalculations based on strain compatibility byFig. 5.2.5 in the PCI Design Handbook.

3. The bilinear concept for predicting thedeflection of cracked prestressed members wasconservative well beyond a nominal bottom fibertensile stress of 12i,/ f'c.

4. Composite action between the precast andcast-in place portions was evident up to ultimateload. The top surface of the precast slab was a smooth,even, machine cast finish and did not comply withSection 17.7 of ACI 318-71. There was noreinforcing steel projecting from the precast slabinto the topping concrete.

5. A shear failure did not occur even though theultimate shear stress vu was 1.75 times vc as computedin accordance with ACI 318-71.

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I--00WZJW 500a-U)a ]J

4000Jaw000a _Mo:wa(n 000w _Ja 100

InitiaV 1 ^loading

22.625000 psiopping.0 .0.0 .700 psiprecast23.875

5 layers co nc. b lks = 540 plf

4ayers conc.blks = 432 plf

.Intia loading3 layers co nc b lks = 324 plf

Reloading/ I /2ayers conc . blks = 216 pifUnloading

layer c o n c . blks = 108 plf

Reloading

+ I1" -2 -3" -4 -5' -67" -8 -9" -10 -II"-12 -13"-14-15"CAMBEREFLECTIONFig. 1. Loa d-deflection curvesAt this time in the development of pre-stressed concrete it does not seem nec-essary to perform a load test of a wide-ly used pretensioned member. But aconscientious producer of Spiroll hol-low core slabs in La Crosse, Wisconsin(Hemstock Prestressed Inc.) asked fora load test just to confirm that theywere still producing a quality product.

The resulting load test was routineand the slab performed as expected butit also verified a numb er of design prac-tices and provisions of the 1971 ACIBuilding Code (ACI 318-71).The test member was an 8 in. deep24 in. wide machine made hollow coreslab with a 2 in. concrete topping (seeFig. 1). The precast pretensioned slab

PCI Journal/March-April 1973 5


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C) Table 1. Comparison of observed and calculated deflections for various loading stages

Load stage Calculated bottomfiber stress, psi Calculateddeflection frominitial camber, in.Calculateddeflection fromlevel, in.

Observeddeflection fromlevel, in. RemarksNo load 650 (comp ression) 0 -0.67* 0.661 layer of conc rete block108 lb per ft 75 (c ompression) 0.36 +0 .31 t +0.282 layers of concrete block216 lb per ft 499 (tension) 0.71 0. 04t 0.093 la yers o f c o nc rete blo c k C ra c king oc c urred324 lb per ft 1074 (tension) 1.07 0 . 4 0 t 1.72 while placing this

layer of b lockNo load 650 (c ompression) 0 +0.67* 0.40$1 layer of conc rete block108 lb per ft 75 (c ompression) 0.36 +0.31 t 0.152 layers of conc rete block Cracks reopened216 lb per ft 499 (tension) 0.71 +0.04t 0.60 while placing3 layers of conc rete block this layer of block324 lb per ft 1074 (tension) 1.07 0 . 4 0 t 1.724 layers of co ncrete block Further flexural432 lb p er ft 1649 (tension) 1.42 0. 76t 4.97 crac king but noshear cracks5 layers of conc rete block540 lb p er ft 2224 (tension) 1.78 1 .1 1 t 15.35 Slab graduallysettled to floo r

* Camber calculated with elastic materials properties indicated 0.62 in. Value here is obtained using multipliers to account for creep and prestress losses. See com-puter output in the Appendix.Values calculated are based on gross section properties. Crackin g occurred when the net tensile stress in the bottom fiber w as near 619 psi or 7.5 -\/t'. After crack-0ing, section properties are greatly reduced and observed deflection values are accordingly larger than calculated. See the deflection calculations in the Appendix andFig 2.

$ Slab returned to within 0,26 in. of cambered position. Some creep set apparently occurred. With more time part of this set would probably have disappeared.


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was taken from stock and consequentlythere was no opportunity to determinethe concrete properties at time of mix-ing or the stressing provisions. Similar-ly, the concrete topping was cast with-out concrete cylinders so compressiontests could not be used to verify thestrength of the topping.Such a situation would seriouslyhandicap any serious research study butthis problem is typically encountered inthe load testing of existing structures.A straight strand pretensioned floorslab can be easily checked after castingfor dimensions, section properties, num-ber, location, and size of strands. Theconcrete properties were determinedwith a concrete impact hammer. Thedimensional measurements and the im-pact hammer data were sufficient toaccurately determine the structural be-havior and strength of the slab.It is unfortunate that we encounterso much suspicion and mistrust of theconcrete impact hammer (Swiss ham-mer) within the engineering profession.Frequently we find engineers who willput almost blind faith in concrete testcylinders as representing the concretein a structural member but will rejectimpact values taken directly on themember. Cores taken from concretemembers frequently furnish erratic re-sults but these too are usually givenmore credibility than impact values.The impact hammer is a practical meth-od for determining the concretestrength of machine-made slabs andconsiderably more accurate than testcylinders. This is because the compac-tion of the machine cannot be accurate-ly duplicated in making the cylinders.In my opinion the concrete impacthammer should be the standard methodfor determining compressive strength inmachine-made slabs.

The hollow core slab tested was pre-stressed with four 1/zin. diameterstrands having an ultimate catalogstrength of 250,000 psi. The precast

member is made with normal weightconcrete consisting of limestone coarseaggregate and natural sand fine aggre-gate. At the time of the test the precastslab had reached a compressivestrength of 6700 psi and the topping,3000 psi. Both of these strength valueswere obtained by a concrete impacttest hammer. An average of 8 readingswere taken on the slab and 11 readingson the topping.It should be noted that the impacthammer readings were taken on theside of the floor member with the in-strument in the horizontal position. Thecorrelation to 6 x 12 in. compressioncylinder strengths was made with theuse of curves printed on a plate at-tached to the instrument. Obviously, itwould have been better to have a cor-relation curve based on conc retes mixedfrom local materials but such data werenot available. Impact readings taken onhollow core floor and roof assemblieswith the instrument in the vertical posi-tion are not as reliable as horizontalreadings because of the presence of thecores. The cores tend to "soften" thehammer impact and hence indicatelower than actual compressivestrengths. Again, this is a serious handi-cap in evaluating the strength of hol-low core members in place on a build-ing but with a single slab we had nodifficulty obtaining reliable values fromthe sides of the slab.

DESCRIPTION OF TESTThe hollow core floor assembly was33 ft long and the slab was placed onsupports to provide a 31.5 ft clear span.One end of the slab was placed on asteel roller to eliminate the effects ofhorizontal friction which would be in-duced on a rigid support as the slabdeflects. If these frictional forces arenot eliminated, a negative moment isinduced at the supports and can affectthe results of the test. The roller end

PCI Journal/March-April 19737


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support consisted of two plates with a1 in. steel rod sandwiched between.The lower plate was supported by 6 x 8in. solid concrete blocks stacked twohigh such that the support was about15 in. above the floor. Deflection read-ings were taken with the aid of a transitlocked in the horizontal position and alevel rod reading in feet, inches, andeighths of an inch. Prior to the test,readings were taken at each end of theslab and in the center.

TEST LOADSBefore commencing the test it wasdetermined that the slab would proba-bly take about 500 lb per linear ft atfailure. This determination was quicklymade by a time-sharing computer. Thedata obtained from measurements onthe test slab were telephoned to our of-fice and the computer results were tele-

phoned back within a half hour. Beforethe availability of the computer it wasoften not possible to compare actual re-sults with analytical values until some-time after the test. In this case we couldmake comparisons as the test pro-gressed. It was decided to load the slabin five increments and these loadswould be applied using solid concreteblocks. The blocks were 55/s x 7 5/s x15 5/8 in. (nominal 6 x 8 x 16 in.). Tenblocks were weighed and the averagewas 54 1/s lb per block. It was thereforeassumed that each block would weighan even 54 lb each. The test slab wasmarked off with 21 equal spaces, 11/zft long over the 31V2 ft span. Since theslab was nominally 2 ft wide, each ofthe 21 rectangles represented 3 sq ft.By placing three 6 x 8 in. blocks in eachof these rectangles, each block repre-sented the load applied per square foot.In other words, one layer of blockplaced on the slab within these rectan-gles would represent 54 lb per sq ft or108 lb per linear ft. After each layer ofblock was placed on the slab, deflectionreadings were taken.

TEST RESULTSTable 1 shows the results of the five-

stage load test. The slab was first load-ed up to Stage 3 which consisted of 324lb per linear ft and the blocks were re-moved to determine the recovery. Thereason for this step is that ACI 318-71provides for a procedure to evaluate thestrength of existing structures. Part 6 ofthe ACI Building Code specifies thatthe structure shall be subjected to aload consisting of 0.85 (1.4D + 1.7L).This load is to be left on the structurefor 24 hours and the deflection readingstaken. If the measured maximum de-flection of a prestressed member ex-ceeds 12 /20,000h, the deflection re-covery within 24 hours after the remov-al of the test load shall be at least 80percent. In this case the 12/20,000hequals 0.715 in. It will be noted fromTable I that under the third stage loadour deflection was 1.72 + 0.66 =2.38 in. from the cambered positionwhich exceeds the value specified bythe ACI Code. Although it was notpractical to hold the load on for 24hours in this case, the recovery wasnevertheless observed. It can be seenfrom Table 1 that the member wentback to within 0.26 in. of its originalcambered position. This is an 89 per-cent recovery.Table 1 shows that the slab initiallyhad 0.66 in. of camber under its owndead load. The calculated camber valueas shown on the computer sheets in-cluded in the Appendix was 0.67 in.(0.68 in. at erection, 0.66 in. final).For the first two load stages the com-puter output shows that the bottom fi-ber stress would be less than the modu-lus of rupture (7.5Vf',) and thereforeelastic deflection behavior could be ex-pected. The member performed almostexactly as calculated, as can be seenfrom Table 1. Under the first load stageit was anticipated that 0.36 in. of de-flection would occur from the cam bered

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Load stage 5 540 plf

Load stage 4 432 plf

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the 7.5\/j' value seems reliable whenapplied to this type of prestressed mem-ber. After removal of the concreteblocks for the third load stage, the slabwas reloaded for Stages 1, 2, and 3.Since the slab had cracked during thefirst loading it could be expected thatthe cracks would reopen when the nettensile stress in the bottom became ze-ro. Computer calculations in the Ap-pendix show that this net tensile stressin the bottom corresponds to a super-imposed load of about 122 lb per linearft. It can be noted from Fig. 1 that thereloading curve begins to break awayfrom the straight line at about 122 lbper linear ft. When the third layer ofblocks was applied, the slab returnedexactly to the position that was ob-served for the first loading. This be-havior is consistant with the results ofmany other load tests involving the re-loading of previously cracked pre-stressed members. The next two layersof block were added with the results asshown in Table 1. Further flexuralcracking occurred during both of thesestages but there was no evidence ofshear cracking or separation of the com-posite slab from the precast portion ofthe member. Failure of the slab oc-curred very near the time when the lastblock was applied near midspan for thefifth load stage. The failure was gradualand was the result of yielding of theprestressing strand. Following this ten-sile failure the topping buckled at mid-span and separated from the precastslab about 6 ft each side of the center-line.As can be seen from the ultimatemoment calculations, the observed ulti-mate moment is first determined andthen the ultimate moment is calculatedbased on the two methods prescribedby ACI 318-71. The first calculations,based on Eq. (18-3) for f r , s ,he steelstress at ultimate, underestimates theobserved ultimate moment. The secondcalculation, based on strain compatibil-

ity making use of the design aid in thePCI Design Handbook (Fig. 5.2.5),shows much better agreement with theobserved ultimate moment. The deflec-tion behavior and ultimate flexuralstrength clearly demonstrated that fullcomposite action was present up to theultimate load. The precast slab had asmooth top surface finished by the vi-brating screed that is part of the Spirollmachine. The surface obviously did notcomply with the surface roughness re-quirements of Section 17.7 in ACI 318-71. It is not practical to provide pro-jecting steel from a machine cast slaband of course none was provided.From the computer output in theAppendix, it should be noted that atthe final load stage (540 lb per linearft) the shear stresses were very highyet no shear distress occurred. It can benoted from the output that at a pointapproximately 3 ft from a support theshear stress in the member was 137 psiover the value specified for plain con-crete. This is considerably in excess ofwhat the ACI Code allows for beamswithout the use of reinforcing steel. Forbeams without stirrups, Section 11.1 ofthe ACT Code says that v,2, must be lessthan one-half v, but slabs and footingsare exempted from minimum shearsteel requirements. In this test v,, was1.75 v 0 at ultimate load. The load testproved that the code exemption forslabs is justified and applicable to ma-chine made hollow core slabs. In de-signing machine made slab floor sys-tems with high shear stresses it shouldbe recognized that accidential crackingor web tearing could be present andcould reduce the shear strength. Thetest, nevertheless, shows that theseslabs do possess a substantial shear re-sistance w ithout web reinforcem ent.

DEFLECTIONThe deflection calculations relate toLoad Stages 2 and 3. The computer

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output sheets also calculate deflectionsbut these computations are alwaysbased on the assumption of a gross sec-tion. Up to cracking this procedure isaccurate as can be seen from Table 1.After cracking, the moment of inertiais substantially reduced and deflectioncalculations based on the gross momentof inertia will be unconservative as canhe seen from Table 1.The ACI Building Code in Section1.8.4.2(c) states that when the net ten-sile stress is 12Vf', a bilinear momentdeflection relation must be used to cal-culate deflections. This relation isshown in the Appendix as well as inFig. 2. The actual moment-deflection(or load-deflection or bottom fiberstress-deflection) diagram is approxi-mated by two straight lines. The firstline has a slope proportional to thegross mom ent of inertia Igand the slopeof the second line is proportional to thecracked moment of inertia I,, the twolines joining at the point correspondingto a net tensile stress of 7.5^/f',. Thisbilinear approximation was first devel-oped by the PCI Committee on Allow-able Stresses and adopted for the ACIBuilding Code.

The calculations show that with thisprocedure the deflection at Load Stage3 would be 2.32 in. The observed de-flection was 1.72 in. so the bilinearmethod overestimates deflection at thisstress level (-1074 psi or 13Vr) andhence is conservative. At Load Stage 4(bottom fiber stress 1649 psi or 20i/)the calculated deflection is 4.84 in.and the observed deflection was 4.97in. Above this load or tensile stress levelthe bilinear method would greatly un-derestimate the actual deflection. Thebilinear method is apparently satisfac-tory for predicting deflections for thisproduct within the service load range.In my opinion it is just as simple andmore useful to calculate cracked de-flection using the two-step approach

rather than the effective moment of in-ertia method proposed in the ACI C o m -mentary and presented in the PCI De-sign Handbook .

CONCLUSIONSThe results of this test reemphasizethat the ultimate flexural capacity ofprestressed members can be predictedvery precisely using the provisions of

the ACI Building Code. The slab testedon a 31.5 ft span carried 270 lb per sqft (540 lb per linear ft) at flexural fail-ure. At service load, cracking will notoccur and the behavior can be judgedfrom Table 1 for Stages 1 and 2 loadingconditions. The test further demon-strated substantial shear strength capa-bilities for this member when used inconjunction with a 2 in. concrete top-ping of modest strength. Additionally,the test confirms that the bilinear meth-od of predicting deflection behavior inthe cracked range is conservative up to12 \/f', and beyond. In all respects, themember exhibited a behavior that is invery close agreement with the resultsexpected from calculations.

APPENDIXUltimate moment calculations

The ultimate moment observed is:M u = 1.5(w n + w sz )L2= 1.5(160 + 540 ) (31.5)2= 1,040,000 in.-lb

To compute the ultimate momentcalculated use Eq. (18-3) of ACI 318-71. For bonded members:fps=fpu-0.5pl,fr, U l

fps _Aps fluPe f',d f0_(0.144)50 (22.625)(8.56) 3 = 0.25PCI Journal/March-April 19731


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LOAD ORMOMENT ORBOTTOMFIBER

STRESS

12HIS SLOPE ISA FUNCTION OFCRACKED MOMENTOF INERTIA

CHANGE OCCURS WHEN BOTTOMFIBER STRESS REACHES NETTENSILE STRESS = 7.5/C

THIS SLOPE IS A FUNCTION OFGROSS MOMENT OF INERTIA

DEFLECTION

Fig. Al. Bilinear mom ent-deflection diagram

The ultimate steel stress isfp s= 250 [1-0.5(0.25)]

= 219 ksiTo determine the true ultimate mo-ment, the 0 factor must be ignored.

M,, = Apsd(1-0.59Wr)A ,ps^p =bd f,

_ 4(0.144)1922.625(8.56)= 0.22M,, = 4(0.144)(219)(8.56) x[1 0 .59(0.22)]= 940,000 in.-lb

From the PCI Design Handbook(Fig. 5.2.5) determine fp sy straincompatibility.W,- bd . f'u -0.25

Now C = 1 for 3000-psi concreteand therefore Ca 0.25.

From the chart (bottom of Fig. 5 .2.5),fps/fpu = 0.93.

fp s = 0.93(250) = 235 ksiM ,, = 4(0.144)(235)(8.56) X

[1 0.59(0.235)]= 1,000,000 in.-lb

Thus, the ultimate moment usingthe strain compatibility method closelymatches the observed ultimate moment.Deflection calculations

Calculate the deflection using thebilinear mom ent- deflection relation (seeFig.l),s specifiednection18.4.2(c) of ACI 318-71.Use the PCI Design Handbook tocalculate Icracked-_g 29,000,000

= 6.15^ aE,716,000_ Aps_ 4(0.144) .003Ppd 22.625(8.563)

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npp= 6.15(0.003) = 0.0185From Fig. 5.2.27, C = 0.17.

bd3'cracked = C 12

_ 0.17(22. 625) (8.563)312

= 201 in.47.5 /6700=219 psi

Find the load at 619 psi by averag-ing the conditions at Load Stages 2and 3.

Stage 2 Tensile stress = 499 psi2161b,499 psi19L1 =187 Ib

Stage 3 Tensile stress = 1074 psi324 lb _ L21074 psi19

L 2 =268 lbzThe average of these two conditionsis 228 lb.

5wL4^l 384EIy5(228)(31.5)4(1728)

384(4,716,000)(1427)= 0.75 in.

From this deflection deduct the ini-tial camber (calculated) of 0.67 in.Therefore, the net deflection is 0.08in.Next, (calculate the deflection at

Load Stage 3 ( f b = 10 74 psi, tension).The applied load after cracking is:324 228 = 96 lb per ft5wL4384EIercked

5(96)(31.5)4(1728)384(4,716,000)(201)

= 2.24 in.To this deflection add i = 0.08 in.Thus, the total calculated deflectionis 2.32 in.From Table 1, the observed deflec-tion is 1.72 in.But, the allowable stress is 12Vf'e= 997 psi.Therefore, the bilinear method isconservative at this level.Finally, calculate the deflection atLoad Stage 4 (fn = 1469 psi, tension).The applied load after cracking is:432 228 = 204 lb per ft

_ 5(204)(31.5)4( 1728)384(4,716,000)(201)

= 4.77 in.To this deflection add A 1 = 0.08 in.Thus, the total deflection is 4.85 in.From Table 1 the observed deflec-tion equals 4.97 in.Therefore, the bilinear method isvery close at this stress level on thisfloor system.

(See pp. 74-77 for typical computer output.)

Discussion of this paper is invited.Please f orw ard y our discussion to PC I Headquarters by A ugust 1, 1973, topermit publication in the September-October 1973 issue of the PCI JOURNAL.PCI Journal/March-April 19733


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Table Al. Typical computer output

THE CONSULTING ENGINEERS GROUPi INC.PRESTRESSED CONCRETE MEMBER DESIGN--PAGE 1

PROJECT;ESIGNER:DATE:SECTION:WIDTH(B)= 24.00 DEPTH(H) =.00 WEB(8W) =.00TOPPING WIDTH= 22.63HICKNESS= 2.00SECTION PROPERTIESPLAINOMPOSITE*A= 107O.IN. 137 SO.1N.I= 832 IN.4TH 1427 IN.4THY8= 4.00 IN 5.10 1N

YT= 4.00 IN 4.90 1NZ8= 208 1N.3RD 280 IN.3RDL1= 208 IN.3RD 291 1N.3RDW= 108 PLF 153 PLF*DIFFERENCE 1N MODULUS O F 'ELASTICITY OF TOPPING INCLUDED

CONCRETE STRANDWT=45 PCF AREA=144 SC IN PER STRANDFC=700 PSI FPU=50 KSIEC=716 KSI NO. OFTRAND=FCI= 3500 PSI INITIAL LOSS=0 PCTEC1= 3409 KSI FINAL LOSS=0 PCT

P1=01IPSTOPPING Pu=1IPS

WT=45 PCF P=1IPSFC= 3000 PSI END ECCENTRICITY=.56 INEC= 3156 KSI CTR ECCENTRICITY=.56NECC AT 0.4L=.56NLOAD STAGE 1SERVICE DEAD LOAD=PSFPLF EXCLUDING TOPPINGLIVE LOAD=7 PSF08 PLFSPAN= 31.50 FlSERVICE LOAD MOMENTSMIDSPAN 0.4L

MDL= 160 K-IN 15 4 K-iNMSDL= 0 K-1N 0 K-INMTOP= 68 K-IN 65 K-iNTOIL= 228 K-IN 219 K-INMLL= 161 K-IN 15 4 K-INTOIL= 389 K-1N 373 K-1N

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Table Al (cont.) . Typical comp uter outp ut

STRESSESRELEASEEND MIDSPANFB FT FB FTP/A 848 848 848 848PE/Z 1117 -1117 1117 -1117MDL/Z -771 771(MTOP+MSDL)/ZMLL/ZTOTAL 1964 -269 1193 502ALLOWABLE 2100 -177 2100 2100

CAMBER

SERVICE LOADSMIDSPAN 0.4LFB FT FB FT754 754 754 754992 -992 992 -992

-771 771 -740 740-326 326 -313 313-575 552 -552 52974 1410 141 13443015 3015 3015 3015

RELEASE MULT ERECTION MULL FINALPRESTRESS 1.46 1.65 2.41 2.20 3.22MEMBER WT -.84 1.75 -1.47 2.50 -2.10NET .62 .94 1.11SERVICE DL -.26 1.75 -.45NET .68 .66SERVICE'LL -.36NET .31

SHEARLOCAT10N VU VC VU-VC (VU-VC)BW00 143.7 409.3 -265.6 -15941.58 129.3 349.5 -220.2 -13213.15 114.9 190.0 -75.1 -4504.72 100.6 163.7 -63.1 -3796.30 86.2 163.7 -77.5 -4657.87 71.8 163.7 -91.9 -5519.45 57.5 163.7 -106.2 -63711.03 43.1 163.7 -120.6 -72412.60 28.7 163.7 -135.0 -81014.47 14.4 163.7 -149.3 -89615.75 .0 163.7 -163.7 -982

LOAD TO PRODUCE ZERO BOTTOM FIBER STRESSSERVICE DEAD LOAD= 0 PSF .0 PLF EXCLUDING TOPPINGLIVE LOAD= 65 PSF 122 PLFSPAN= 31.50 FT

SERVICE LOAD MOMENTSMJDSPAN 0.4LMDL= 160 K-1N 154 K-1NMSDL= 0 K-IN 0 K-INMTBP= 68 K-1N 65 K-INTOTL= 228 K-1N 219 K-iNMLL= 182 K-IN 174 K-1NTDTL- 410 K-1N 393 K-IN

PCI Journal/March-April 1973 75


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Table Al (cont.). Typical computer output

STRESSESRELEASE SERVICE LOADSEND MIDSPAN MIDSPAN 0.4LFB FT FB FT FB FT FB FTP/A 848 648 848 848 754 754 754 754PE/Z 1117 -1117 1117 -1117 992 -992 992 -992MDL/Z -771 771 -771 771 -740 740(MTOP+MSDL)/L -326 326 -313 313MLL/Z -649 623 -623 598TOTAL 1964 -269 1193 502 0 1481 70 1412ALLOWABLE 2100 -177 2100 2100 -962 3015 3015 3015

CAMBERRELEASE MULT ERECTION MULT FINALPRESTRESS 1.46 1.65 2.41 2.20 3.22MEMBER WT -.84 1.75 -1.47 2.50 -2.10NET .62 .94 1.11SERVICE DL -.26 1.75 -.45NET .68 .66SERVICE LL -.40

NET 26

SHEARLOCATION VU VC VU-VC (VU-VC)BW.0 0 152.3 409.3 -257.0 -15421.58 137.0 349.5 -212.4 -12753.15 121.8 190.0 -68.2 -4094.72 106.6 163.7 -57.1 -3436.30 91.4 163.7 -72.3 -434

7.87 76.1 163.7 -67.6 -5259.45 60.9 163.7 -102.8 -61711.03 45.7 163.7 -116.0 -70812.60 30.5 163.7 -133.3 -80014.17 15.2 163.7 -148.5 -69115.75 .0 163.7 -163.7 -982LOAD STAGE 5 - ULTIMATE LOAD

SERVICE DEAD LOAD= 0 PSF 0 PLF EXCLUDING TOPPINGLIVE LOAD= 286 PSF 540 PLFSPAN= 31.50 FT

SERVICE LOAD MOMENTSMIDSPAN 0.4LMDL= 160 K-IN 154 K-IN

MSDL= 0 K-1N 0 K-INMTOP= 68 K-1N 65 K-INIOTL= 228 K-IN 219 K-INMLL= 804 K-1N 772 K-1N101L= 1032 K-1N 991 K-1N

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Table Al (cont.). Typical computer output

STRESSESRELEASE SERVICE LOADSEND MIDSPAN MIDSPAN 0.4LF8 FT FB FT FB FT FB FTP/A 848 848 848 848 754 754 754 754PE/Z 1117 -1117 1117 -1117 992 -992 992 -992MDL/Z -771 771 -771 771 -740 740(MIP+MSDL)/Z -326 326 -313 313MLL/L -2874 2758 -2759 2647TOTAL 1964 -269 1193 502 -2225 3616 -2066 3462ALLOWABLE 2100 -177 2100 2100 -982 3015 -962 3015

CAMBER

RELEASE MOLT ERECTION MULT FINALPRESTRESS 1.46 1.65 2.41 2.20 3.22MEMBER WT -.84 1.75 -1.47 2.50 -2.10NET .62 .94 1.11SERVICE DL -.26 1.75 -.45NET .68 .66SERVICE LL -1.78NET -1.11

SHEARLOCATION VU VC VU-VC (VU-VC)BW0 0 408.6 409.3 -.6 -41.58 367.8 349.5 18.3 1103.15 326.9 190.0 136.9 8214.72 286.0 163.7 122.3 7346.30 245.2 163.7 81.5 4897,87 204.3 163.7 40.6 2449.45 163.5 163.7 -.3 -211.03 122.6 163.7 -41.1 -24712.60 81.7 163.7 -82.0 -49214.17 40.9 163.7 -122.8 -73715.75 .0 163.7 -163.7 -982

performance of pc slab

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