Shear-bond Strength of Studded Steel Deck Slabs

Transcription

1 Missuri University f Science and Technlgy Schlars' Mine Internatinal Specialty Cnference n Cld- Frmed Steel Structures (1984) - 7th Internatinal Specialty Cnference n Cld-Frmed Steel Structures Nv 13th Shear-bnd Strength f Studded Steel Deck Slabs Max L. Prter Lwell F. Greimann Fllw this and additinal wrks at: Part f the Structural Engineering Cmmns Recmmended Citatin Prter, Max L. and Greimann, Lwell F., "Shear-bnd Strength f Studded Steel Deck Slabs" (1984). Internatinal Specialty Cnference n Cld-Frmed Steel Structures This Article - Cnference prceedings is brught t yu fr free and pen access by Schlars' Mine. It has been accepted fr inclusin in Internatinal Specialty Cnference n Cld-Frmed Steel Structures by an authrized administratr f Schlars' Mine. This wrk is prtected by U. S. Cpyright Law. Unauthrized use including reprductin fr redistributin requires the permissin f the cpyright hlder. Fr mre infrmatin, please cntact schlarsmine@mst.edu.

2 Seventh Internatinal Specialty Cnference n Cld-Frmed Steel Structures St. Luis, Missuri, U.S.A., Nvember 13-14, 1984 SHEAR-BOND STRENGTH OF STUDDED STEEL DECK SLABS by Max L. Prtera Lwell F. Greimann a SUMMARY The shear-bnd strength f cmpsite deck slabs was increased by 8% t 33% by studs lcated at the end f the span. A design apprach utilizing a linear regressin fr nnstudded specimens als appeared reasnable fr the studded slabs. INTRODUCTION The use f cld-frmed steel decking as reinfrcement fr cncrete flr slabs has increased markedly in the past twelve t fifteen years. This kind f cmpsite flr system has tw primary advantages: the ability f the steel deck t prvide frmwrk during the casting stages f the cncrete and the ability t serve in cmpsite actin as tensin reinfrcement under psitive bending. Cmpsite shear transfer devices such as deck embssments r transfer wires prvide restraint fr hrizntal shear which develps at the deck-t-cncrete i.nterface. Many ther advantages in additin t thse mentined abve are given in Ref. [7]. Design recmmendatins fr vertical lads applied t frmed metal deck cmpsite slabs have been develped at Iwa State University [8]. The design is cntrlled primarily by ne-way behavir; that is, the relatively large bending stiffness f the slab parallels the lngitudinal directin f the deck. Previus research at Iwa State University [6-10] has resulted in design equatins [8] fr predicting the lad capacity f ne-way steel-deck-reinfrced cmpsite slabs withut end-span studs. The predminant mde f failure was fund t be shearbnd [10]. The design equatin fr shear-bnd capacity predictin was based n a mdificatin f Eq. (11-6) f the American Cncrete Institute (ACI) Cde [1]. Fr steel deck slabs that have end-span studs, tw types f cmpsite behavir need t be cnsidered. A general view f such a flr slab system with bth cmpsite deck and studs is shwn in Fig. 1. Past research n cmpsite steel deck slabs has nt cnsidered the effect f stud end restraint n shear-bnd behavir. Als, past aprfessr, Civil Engineering Department, Iwa State University, Ames, Iwa. 285

3 286 SEVENTH SPECIALTY CONFERENCE research and resulting design criteria n cmpsite decks with studs haye cncentrated n the cmpsite actin f the beam and supprt girder and did nt cnsider the slab actin [2,3,5]. This paper will fcus n the influence f end-span studs n steel-deck-reinfrced cmpsite slabs subjected t vertical lading. This wrk was part f a prject spnsred by the Natinal Science Fundatin n "Seismic Resistance f Cmpsite Flr Diaphragms" [11] and the details f the wrk perfrmed are described in Ref. [4]. TEST PROGRAM T determine the influence f end-span studs n steel-deck-reinfrced cmpsite slabs, several specimens were subjected t tw-pint lading, as illustrated in Fig. 2. Identical slabs withut end studs were tested t prvide a basis fr cmparisn. A ttal f fifteen specimens were cast and tested in this phase f the ISU study; hwever, the experience gained and the analysis prcedures develped frm the previus wrk [10] were applied in the analysis f these test results. In general, the shear-bnd mde f failure is characterized by the frmatin f a diagnal tensin crack in the cncrete at r near ne f the lad pints, fllwed by a lss f bnd between the steel deck and the cncrete, resulting in visible slip at ne end f the span, as illustrated in Fig. 3. The term shear-bnd was applied t this type f failure because f the simultaneus ccurrence f bth the shear and bnd failures. Shear-bnd failure results in a lss f cmpsite actin and hrizntal slippage ver the regin f the shear span length, L', as shwn in Fig. 3. The assciated end-slip indicated in the figure results frm the cncrete mving hrizntally and verriding, r failing, the shear transfer device. The additin f studs at the end f a shear span t prvide cmpsite actin between the slab and supprt beam culd be expected t prvide restraint against the end-slip assciated with shear-bnd failures. Thus, the primary gals f this study included: 1. Determining the percentage f lad increase fr studded versus nnstudded ne-way slab element specimens, 2. Determining the behaviral characteristics fr the studded specimens as distinguished frm nnstudded nes, 3. Develping an analysis prcedure fr the predictin f the ultimate lad f the steel deck specimens cntaining studs. Test Specimens All fifteen specimens were nminally 3 feet wide (91.4 cm), had an verall thickness f 5-1/2 inches (14 cm), and were reinfrced with

4 SHEAR-BOND STRENGTH OF SLABS inch (7.6-cm)-deep steel decking f either 16- r 20-gage thickness. The fifteen specimens were divided int fur grups n the basis f the ut-t-ut length f the specimen and the deck gage as shwn in Table 1. Each grup included tw studded specimens tgether with either ne r tw nnstudded cmpanin specimens fr cmparisn. Each f the studded specimens cntained typical headed studs, 3/4 inch (1.9 cm) by 4-7/8 inches (12.4 cm), placed in the dwn crrugatin 3 inches (7.6 cm) in frm the end f the specimen, as illustrated in Fig. 4. Tw studs were welded thrugh each end f the deck t 1/2- inch (1.3-cm) by 6-inch (15.2-cm) by 36-inch (9l.4-cm) steel plates with the same stud and burnff height typically used in full-scale tw-way slabs. The lading apparatus was designed t prvide twpint line lading, as illustrated in Fig. 2. Test Lading and Measurements In additin t lad measurements, behaviral determinatins were made fr: 1. vertical deflectin, 2. end-slip displacements between the deck and cncrete interface, 3. slip between the deck and supprt plate, and 4. specimen strains. The vertical displacements were determined at the center f the specimen and under the tw lad pints. The ultimate lads (P u ) recrded fr each specimen are shwn in Table 2. The studded specimens shwed a significant increase in ladcarrying capacity cmpared t their nnstudded cmpanin specimens. Fr the 60-inch (1.52-m) shear spans, Grups I and IV, the increase was 7.7% and 24.5%, respectively. Fr the l8-inch (45.7-cm) shear spans, Grups II and III, the increase was 32.5% and 30.5%, respectively. ANALYSIS Shear-Bnd Analysis Strength relatinships fr the predictin f shear-bnd have been prpsed [7,10] frm previus tests. These relatinships use a cmbinatin f the basic parameters t prvide a linear regressin equatin such as that illustrated by Fig. 5. Frm the figure a linear relatinship can be written as

5 288 SEVENTH SPECIALTY CONFERENCE V e bd (1) where V is the experimental shear strength, b is the specimen width, d is th effective depth, p is the reinfrcement rati, l' is the shear span (as illustrated in Fig. 2), f' is the cncrete strength, mi is the slpe f the regressin line itfig. 5, and kl is the rdinate intercept f the regressin line in Fig. 5. Fr design purpses the experimental regressin line shwn in Fig. 5 is reduced t btain new values fr m and k t prvide fr a design equatin similar t that f Eq. (1) but with reduced m and k values. Design standards based n the research perfrmed at Iwa State University [7] and currently being develped by the American Sciety f Civil Engineers thrugh their Technical Cuncil n Cdes and Standards are scheduled fr publicatin in the near future. Analysis f the Specimens Tested The shear-bnd analysis apprach described abve (as shwn in Fig. 5) was als applied t the studded and nnstudded specimens tested in this series. Tw appraches were tried in cnnectin with the regressin analysis f the studded specimens. One entailed a prpsed regressin line fr the studded specimens btained by using the same percentage increase fund in the series f tests. The test results and the assciated average percent increase fr the studded specimens are given in Table 2. Figures 6 and 7 shw the final results fr the 20- and I6-gage studded specimens, respectively. The prpsed regressin lines illustrated in these tw figures were derived by using the percentage increase in capacity fund in the stud specimens as shwn in Table 2. As can be seen in Figs. 6 and 7, the I8-inch (45.7-cm) shear span specimens shwed a sizable lad increase ver the value predicted fr the regressin curve indicating the additinal lad cntributin f the stud. Thus, apparently this apprach des nt prvide a cnsistent predictin fr all shear spans. A secnd shear-bnd regressin apprach was frmulated n the basis f a regressin analysis f the studded specimens themselves. The results f this analysis (Fig. 8) shw that the shear-bnd regressin frmulatin apprach appears feasible fr the studded specimens and that the same basic parameter frmulatin may als wrk fr the determinatin f ' the shear-bnd strength fr cmpsite slab decks cntaining studs at the ends f the shear span.

6 SHEAR-BOND STRENGTH OF SLABS 289 BEHAVIOR Vertical Deflectins Generally the flexural behavir exhibited three stages f stiffness, as illustrated in Fig. 9. Stage I in Fig. 9 represents the uncracked stiffness, Stage II represents the cracked stiffness, while Stage III represents the additinal stiffness due t the end restraint, (i.e., due t stud shear restraint when it is present). Fr the deflectins beynd ultimate lad, the studded specimens exhibited greater ductility. Deflectin behavir fr the nnstudded versus studded specimens f Grups III and IV is cmpared in Figs. 10 and 11. End-Slip Displacements The studded specimens prvided a significant lad increase after first slip. Typical lad versus end-slip behavir as illustrated by the Grup IV specimens is given in Fig. 12. Nte that in this figure the studded specimens were able t achieve a slightly mre ductile slip behavir and slipped at a stage prir t ultimate. Failure Mde All f the nnstudded specimens ultimately failed because f a lss f shear-bnd strength. Strains bserved during testing indicated that the bttm fibers f the steel deck had yielded at the center line prir t ultimate fr the specimens in Grups I, III, and IV, even thugh the ultimate failure mde was that f shear-bnd. Large diagnal tensin cracks frmed under a pint f lading, and the cncrete sectin f the shear span slipped hrizntally ver the decking, resulting in the slip bserved at the end f the specimen. All f the studded specimens except ne failed ultimately frm tearing f the deck near the uter perimeter f the entire stud weld. In the ne exceptin, lngitudinal tensin cracks frmed in the cncrete at the studs and prpagated arund the stud, resulting in the cncrete slipping arund the stud. In this case, failure f the cncrete.arund the stud did nt allw tearing f the deck t ccur. SUMMARY AND CONCLUSIONS The tests described in this paper indicated that the additin f end studs increased the lad capacity f ne-way steel-deck-reinfrced slabs by 8% t 33%, depending n the span and gage thickness f the deck. The nnstudded specimens ultimately failed frm a lss f interfacial frce in the shear span. The studded specimens ultimately failed frm tearing f the deck near the stud and slippage between the cncrete and steel ver the length f the shear span. The increase in lad capacity

7 290 SEVENTH SPECiALTY CONFERENCE fr the specimens cntaining studs was attributed t the additinal stud resistance which develped as the cncrete within the shear span attempted t verride the deck embssments. Tw shear bnd analysis appraches were attempted. The first was t find the percent f increase in the measured ultimate shear capacity and apply it t the change in the previusly btained shear-bnd strength regressin curves. This apprach did nt lead t cnsistent predictins fr all shear spans. The secnd was t determine a linear regressin curve fr all specimens cntaining studs fr each gage thickness f deck. This apprach appears t give cnsistent results fr the parameters pltted. Thus, a design apprach similar t that fr nnstudded specimens is reasnable fr thse slab elements cntaining studs at the ends f the shear spans.

8 SHEAR-BOND STRENGTH OF SLABS 291 APPENDIX--REFERENCES 1. American Cncrete Institute, BUilding Cde Requirements fr Reinfrced Cncrete, ACI Standard , Detrit, Michigan: American Cncrete Institute, American Institute f Steel Cnstructin, Inc., "Specificatin fr the Design, Fabricatin and Erectin f Structural Steel fr Building," New Yrk: AISC, Grant, J. A., Fisher, J. W., and Slutter, R. G., "Cmpsite Beams with Frmed Steel Deck," AISC Engineering Jurnal, American Institute f Steel Cnstructin, First Quarter 1977, pp Krupicka, G. L., "The Behavir and Analysis f Steel-Deck-Reinfrced Cncrete Slabs with End-Span Studs," Master's Thesis, Iwa State University, Ames, Iwa, 1979, 97 pp. 5. Ollgaard, J. G., Slutter, R. G., and Fisher, J. W., "Shear Strength f Stud Cnnectrs in Lightweight and Nrmal-Weight Cncrete," AISC Engineering Jurnal, American Institute f Steel Cnstructin, 8, N.2, April 1971, pp Prter, M. L., and Ekberg, C. E., Jr., "Behavir f Steel-Deck Reinfrced Slabs," Jurnal f the Structural Divisin, ASCE, Vl. 103, N. ST3, Prc. Paper 12826, March 1977, pp Prter, M. L., and Ekberg, C. E., Jr., "Cmpendium f ISU Research Cnducted n Cld-Frmed Steel-Deck-Reinfrced Slab Systems," Bulletin 200, Engineering Research Institute, Iwa State University, December Prter, M. L., and Ekberg, C. E., Jr., "Design Recmmendatins fr Steel Deck Flr Slabs," Jurnal f the Structural Divisin, ASCE, Vl. 102, N. ST11, Prc. Paper 12528, Nvember 1976, pp Prter, M. L., and Ekberg, C. E., Jr., "Design vs Test Results fr Steel Deck Flr Slabs," Prceedings f Third Specialty Cnference n Cld-Frmed Steel Structures, Department f Civil Engineering, University f Missuri-Rlla, Octber 1975, pp Prter, M. L., Ekberg, C. E., Jr., Greimann, L. F., and Elleby, H. A., "Shear-Bnd Analysis f Steel-Deck-Reinfrced Slabs," Jurnal f the Structural Divisin, ASCE, Vl. 102, N. ST12, Prc. Paper 12611, December 1976, pp Prter, M. L., and Greimann, L. F., "Seismic Resistance f Cmpsite Flr Diaphragms," ISU-ERI-Ames-80133, Iwa State University, Ames, Iwa, Final Reprt submitted t Natinal Science Fundatin, May 1980, 174 pp.

9 292 SEVENTH SPECIALTY CONFERENCE APPENDIX--NOTATION A s b Crss-sectinal area f steel deck r area f negative mment reinfrcing steel where used as tensin reinfrcement Unit width f slab Width f cmpsite test slab Effective slab depth (distance frm extreme cncrete cmpressin fiber t centridal axis f the full crss sectin f the steel deck) f' ct k Cmpressive test cylinder strength at time f slab testing Ordinate intercept f reduced shear-bnd line (see Fig. 5) Ordinate intercept f shear-bnd line (see Fig. 5) Length f span L' m Length f shear span; fr unifrm lad, L' span Slpe f reduced shear-bnd line (see Fig. 4) Slpe f shear-bnd line (see Fig. 4) ne quarter f the P e V e p Maximum applied experimental slab lad at failure btained frm labratry tests (includes weight f lading system but nt weight f slab) Maximum experimental shear at failure btained frm labratry tests (nt including weight f slab) Reinfrcement rati f steel deck area t effective cncrete area, A/bd

10 SHEAR-BOND STRENGTH OF SLABS 293 LIST OF TABLES 1. Specimen grups fr vertical lading. 2. Vertical lading test results.

11 294 SEVENTH SPECIALTY CONFERENCE Table 1. Specimen grups fr vertical lading. Specimen Steel Length thickness Grup Specimens (inches) Deck Gage (inches) I 1-4* II III IV *Refers t slab number and type in Table 2.

12 SHEAR-BOND STRENGTH OF SLABS 295 Table 2. Vertical lading test results. Span Shear Span Ultimate Slab Number Length, L Length, L' Lad, P Average % and Type (inches)c (inches) (kips)u Increase 1 - nnstudded nnstudded studded } studded nnstudded nnstudded studded } studded nnstudded nnstudded studded studded } nnstudded studded } studded inch = 2.54 cm kip = 4.45 kn

13 296 SEVENTH SPECIALTY CONFERENCE LIST OF FIGURES 1. Typical cnstructin utilizing cld-frmed steel decking with cmpsite supprt beams. 2. Typical arrangement fr testing ne-way slab elements. 3. Typical shear-bnd failure. 4. Studded specimen details prir t casting. 5. Typical shear-bnd plt shwing the reduced evaluatin f m and k. 6. Prpsed studded specimen curve, 20-gage. 7. Prpsed studded specimen curve, 16-gage. 8. Plt f studded specimen results, gages cmbined. 9. Three stages f bending stiffness. 10. Lad vs. center line deflectin diagram, Grup III. 11. Lad vs. center line deflectin diagram, Grup IV. 12. Lad vs. shear-bnd end-slip, Grup IV.

14 STRUCTURAL 7' CONCRETE ".J COMPOS ITE COLD-FORMED STEEL DECK CELLULAR COMPOSITE COLD-FORMED STEEL DECK Fig. 1. Typical cnstructin utilizing cld-frmed steel decking with cmpsite supprt beams. rn ::x:: : trj Z ::x:: I'%j E rn CO...;J

15 Fig. 2. Typical arrangement fr testing ne-way slab elements. t-:) 00 '" 00 tr.j <: tr.j Z ::t: 00 'i:l tr.j C':l ><: tr.j Z C':l tr.j L

16 SHEAR-BOND STRENGTH OF SLABS 299 STEEL DECK Fig. 3. Typical shear-bnd failure.

17 I L _I 10 1T :0 36" 1 0 : if ;0 I -13". 1-+j3" I- cl ljii/" '\ STEEL DEC; h;2" Fig. 4. Studded specimen details prir t casting 3" r1 O.:l rn t.:j <: t.:j rn "ti t.:j Z >:rj t.:j Z t.:j

18 SHEAR-BOND STRENGTH OF SLABS 301 L' ct Fig. 5. Typical shear-bnd plt shwing the reduced evaluatin f m and k.

19 2.0 l l.4 a 1.2 a V u LL 1.0 bdyf-r STUDDED c (PROPOSED) IN. SHEAR SPAN 60 IN. SHEAR SPAN (x 10-4) L'/F c Fig. 6. Prpsed studded specimen curve, 20-gage l a a 18 IN. SHEAR SPAN 060 IN. SHEAR SPAN L'1f' c Fig. 7. Prpsed studded specimen curve, 16-gage. C;.; r.n t?=:j <: t?=:j z ::t: r.n I-d t?=:j... -< Z t?=:j

20 SHEAR-BOND STRENGTH OF SLABS O.OL Fig. 8. Plt f studded specimen results, gages cmbined.

21 304 SEVENTH SPECIALTY CONFERENCE 5 STAGE II STAGE I DEFL. Fig. 9. Three stages f bending stiffness.

22 SHEAR-BOND STRENGTH OF SLABS 305 GROUP III 16-GAGE DECK 18 IN. SHEAR SPAN FIRST END SLIP (TYPICAL) 40 i \I) Q.. -:..: I I I I I I SPECIMEN 12 STUDDED) 20 Fig. 10. (IN. ) Lad VB. center line deflectin diagram, Grup III. Q...J FIRST END SLIP (TYPICAL) I I I I I I I I SPECIMEN 14 (STUDDED) GROUP IV 16-GAGE DECK 60 IN. SHEAR SPAN OL- -L L CENTER LINE DEFLECTION (IN.) Fig. 11. Lad VB. center line deflectin diagram, Grup IV.

23 306 SEVENTH SPECIALTY CONFERENCE Cl c:(...j Vl CL... 8 SPECIMEN 15 STUDDED) Cl c:( 0...J 4 OL SHEAR-BOND END-SLIP (in.) Fig. 12. Lad vs. shear-bnd end-slip, Grup IV.