design of single plate shear connections

8/12/2019 Design of Single Plate Shear Connections

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Design of Single Plate Shear ConnectionsABOLHASSAN ASTANEH, STEVEN M. CALL AND KURT M. McMULLIN

INTRODUCTIONSingle plate shear connections, often referred to as sheartabs , have gained considerable popularity in recent yearsdue to their efficiency and ease of fabrication. Shear tabconnections are primarily used to transfer beam end reactions to the supporting elements. The connection consistsof a plate welded to a support at one edge and bolted toa beam we b. Figure 1 shows typical applications of singleplate shear conne ctions. This pape r presents the summaryof a research project on the behavior and design of singleplate shear connections. Based on experimental and analytical studies, a new design procedure is developed andpresented.The AISC-ASD^^ as well as AISC-LRFD^^ specifications have the following provisions with regard to shearconnections:Except as otherwise indicated by the designer, connections of beams, girders, ortrusses shall be designed as flexible, and mayordinarily be proportioned for the reactionshears only.Flexible beam connections shall accommodate end rotations of unrestrained (simple)beams. To accompHsh this, inelastic action inthe connection is permitted.

Steel shear connections not only should have sufficientstrength to transfer the end shear reaction of the beam butaccording to above provisions, the connections should alsohave enough ro tation capacity (ductility) to accommodatethe end rotation demand of a simply supported beam. Inaddition, the connection should be sufficiently flexible sothat beam end m omen ts become negligible. Thus, like anyshear connection, single plate shear connections should bedesigned to satisfy the dual criteria of shear strength androtational flexibility and ductihty.Shear-Rotation Relationship in a Shear Connection

To investigate the behavior and strength of a shear connection, it is necessary that realisticshearforces and theircorresponding rotations be applied to the connection. InAbolhassan Astaneh is assistant professor, University ofCalifor-nia, Berkeley.Steven M. Call is graduate researcfi assistant. University ofCalifornia, BerkeleyKurt M. McMullin was graduate researcfi assistant, University ofCalifornia, Berkeley

an earlier research project,^ the shear-rotation relationship for the end supports of simply supported beams wasstudied. A comp uter program was developed^ and used tosimulate increased monotonic uniform loading of thebeams supported by simple connections until the beamscolla psed . 'The studies indicated that the relationship between theend shear and end rotation is relatively stable and dependsprimarily on the shape factor Z^/S of the cross section,L/d of the beam and the grade of steel used. Figure 2shows a series of curves representing shear forces and cor

responding rotations that will exist at the ends of simplysuppor ted be ams. The curves correspond to beams of A36steel having cross sections from W16 to W33 and L/d ra tios of 4 to 38. Also shown in Fig. 2 is a tri-linear curveabe d suggested to be a realistic repre sentative of theshear-rotation curves. The tri-hnear curve abed is proposed to be used as a standard load path in studies of shearconnections. Curve abed is used instead of the moreconse rvative curve aef because it is felt that curveabed represen ts a more realistic maximum span-to-depth ratio for most steel structures. For special cases ofvery large span-to-depth ratio or high strength steels, therotational demand may be greater than that of curveabed . For such cases special care must be taken to assure the rotational ductility demand of the beam is supplied by the connection.

CONCRETE SUPPORTBEAMrLSHEARH TAB W.

JL B E A M - ^SHEAR-^TAB

I J

i 1 laSH EAR - ^TAB 1JC

(a ) (b) ( c )COLUMN

BEAM ^ \

3^^

1

,J TT(d) (e)

Fig. 1. Typical Single Plate Shear Connections

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The shear-rotation curves plotted in Fig. 2 are estab-Ushed based on the assumption of elastic-perfectly-plasticbending moment capacity for the beam. To include the effect of strain hard enin g, the segm ent cd in curve abedis included.The behavior of shear connections has been studied inthe past by several investigators.^'^^ ^^ However, in mostcases, the shear connections have been subjected to moment and rotation or only direct shear without rotation instead of a realistic combination of shear and rotation. Figure 3 shows the shear rotation relationships that existedin several studies including this research project.EXPERIMENTAL RESEARCH

In order to identify limit states of strength and to verifythe validity of the design procedures that were developedand proposed, five full scale beam-to-column connectionassembhes were tested. A summary of the experimentalstudies follows. More detailed information on the researchproject can be found in References 3 and 6.Test S et-up

The test set-up shown in Fig. 4 was used to apply shear-rotatio n relationship of curve abe d in Fig. 2 to the specimens.The main components of the test set-up were a computer based data acquisition and processing system, twoactuators R and S and support blocks. Actuator S, whichwas close to the connection, was force controlled and provided the bulk of the shear force in the connection. Actuator R, which was displacement controlled, provided andcontrolled the beam end rotation.Test Load Path

The proposed standard shear-rotation relationshipshown as curve abe d in Fig. 2 was apphe d to the connec

tions in all of the test specimens. To establish the curve,coupon tests of the plate material were conducted priorto connection tests and the yield point and ultimatestrength of the plate material were obtained. The shearyield capacity of the single plate in each test specimen wascalculated by multiplying the von Miess criterion of shearyield stress, l/VSFy, by the shear area of the plate. Theshear yield capacity of the plate, denoted as Ry,was takenas equal to the shear at point c of curve abe d in Fig.2. Thus the shear yield capacity of the shear tab was assumed to occur when the moment at midspan was equalto Mp. As a. result , a corresponding Mpcan be calculatedfor each connection to be equal to RyL/4. The end rotation of the beam when midspan moment reached Mpwasset equal to 0.03 radians.To establish point b in curve abe d , the shear at thispoint was set equal to AMylL and the rotation was setequal to 0.02 radian. This imphes that when beammidspan moment reaches My, the end rotation will beequal to 0.02 radian. The value of My, the end rotation

will be equal to 0.02 radian . The value ofMyfor each specimen was calculated by dividing M p by the shape factor.A shape factor of 1.12 was used in all specimens.Segm ent cd in Fig. 2 corresp onds to strain hardeningof the beam and the increased moment at beam midspanwhich results in increased shear at the beam ends. To es-tabhsh cd , i t was assumed that when the midspan moment rea ches a value of {FJFy)Mp,the beam end rotationwill be equal to 0.1 radian.In sum ma ry, load path abe d in Fig. 2 reflects the behavior of the beam and its effect on connection shear androtation. Segment ab corresponds to the elastic behavior of beam . At point b , midspan mom ent of the beamreaches My and the beam softens. Segment be corresponds to inelastic beha vior of the bea m. At point c , themidspan moment reaches Mp. Segment cd represen tsextra beam capacity that can develop due to beam strainhardening.

>>RI 0.40F 17)U seA36steel andselect a plate satisfying the following

r e q u i r e m e n t s :a. Ihand /^ > l.Sdi,.b . Lp > laC. tp< 4 / 2 + 1/16d. tp>A^g /Lpe. Bol t spacing =3 in.

(18)(19)(20)(21)

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3. Check effective net section:Calculate allowable shear strength of the effective netarea:R,,==[Lp-n(d,+Vi6)](t,)(03F,) (22)

and satisfy that R^ s ^ R-4. Calculate actual allowable shear yield strength of theselected plate:

R, = LJ, OAOFy) (23)Design fillet welds for the combined effects of shearR oand momentRoûsing Table XIX of the AISC Man ual. ^Cy^ is given in Eq. 16 as:

()(1.0) (16a)e^ = Max (16b)

The weld is designed for a capacity of Ro , and not forthe applied R, to ensure that the plate yields before thewelds. However, for A36 steel and E70 electrodes theweld size need not be larger than VAof the plate thickness.5. Check bearing capacity of bolt group:

{n)(t)(d,){1.2F,) > R (24)If the bolts are expected to resist a moment (as they normally would), this calculation should reflect the reducedstrength as de termin ed by Table X of the AISC Manual^âs demonstrated in the following examples.6. If the beam is cop ed, th e possibility of block shear failure should be investigated.

Application to Design ProblemsThe following examples show how the design procedurecan be implemented into the design of steel structures.

Design Example 1Given:Beam : W27 x 114,t^ = 0.570 in.Beam Ma terial: A36 steelSupp ort: Column flange (Assumed rigid)Reaction : 102 kips (Service Load)Bolts: Vs in. dia. A490-N (snug tight)Bolt Spacing: 3 in.We lds: E70X X fillet weldsDesign a single plate framing connection to transfer thebeam reaction to supporting column.Solution:1. Calculate number of bolts:Shear = R = 102kipsLet us assume M = 0, (will be checked later)n = RI r= 102/16.8 = 6.1

Try 7 bohsThe distance betwe en th e bolt fine and the weld linea is selected equal to 3 in.Check moment:ei, = (AZ -I )I .O - fl = 7 - 1 - 3 = 3.0 in.Mo me nt = 3 x 102 = 306 kip-in.Using Table X of the A ISC-A SD Manual^^ with eccentricity of in., a value of 6.06 is obtain ed for effective num berof bolts (7 bolts are only as effective as 6.06 bolts).Therefore,Rboit = 6.06 X 16.8 = 101.8 102 kips O.K.

Use: Seven ^ in. dia. A490-N bolts.2. Calculate required gross area of the plate:

A^ g = R/OAOFyA^g = 102/(0.40 X 36) = 7.08 in.Ûse A3 6 steel and select a plate satisfying the followingrequirements:a. Ih and / > 1.5Jlh = K =1.5 y8) = 1.32 in.W = f l H - 4 = 3 + 1.32 = 4 .3 2 ;use W =

41/2 in.b . Lp/a > 2.0Lp = 2 X 1.32 + 6 X 3.0 = 20.6 in.;use Lp=21 in.Check: Lp/a = 21/3 = 7 > 2 O.K.c. tp 102kips. O.K.

Use: PL 21x1/2x4^2, A36 Steel.4. Calculate the actual allowable yield strength of the selected plate:Ro = Lptp {OAOFy)Ro = 21 X 0.5 X 0.40 X 36 = 151 kipsDesign fillet welds for the combined effects of shearand moment:Shear = R^ = 151kips

^H; = Max n{1.0) = 7(1.0) = 7 in.a = 3 in.Therefore, e = 7.0 in.Moment = Rê = 151 x 7 = 1057 kip-in.Using Table XIX AISC Manual^^



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a = 7/21 = 0.333Ci = 1.0C = 1.07Di6 = RolCCiLp = 151/(1.0 X 1.07 x 21) = 6.72Since weld size need not be greater than 0.75tp,Use: in. E70 Fillet Welds.

5. Check bearing capacity:For plate:r^ = dbtp(1 .2 FJ = .875 x .5 x 1.2 x 58 = 30.45Rt,rg =6.06(30.45) = 184.5 kips > 102 kips. O.K .Since the beam web is thicker than the plate, the webwill not fail.

6. Beam is not coped , therefore , there is no need for consideration of block shear failure.

Design Example 2Given:Beam:Beam MaterialSupport :React ion:Bolts:Bolt Spacing:Welds:

W16X31, t^ = 0.275A572 Gr. 50 steelCondition of support is unknown33 kips (Service Load)3/4 in. d ia. A 325-N or A49 0 (snug tight)3 in.E70XX fillet weldsDesign a single plate shear connection to transfer thebeam reaction to the support.Solution:1. Calculate number of bolts:Shear = 33 kipsLet us assume M = 0, (will be checked later)Try A325-N bolts with 9.3 kips/bolt shear capacity:n = Rl r^ = 33/9.3 = 3.5Try 4 bolts.The distance between bolt line and weld line a isselected equal to 3 in.Check moment:Since condition of support is not known, the support is conservatively assumed to be flexible forbolt design. Therefore e^ is equal to 3 in.Moment = 3 x 33 = 99.0 kip-in.Interpolating from Table X^^ C -= 2.81Rail = 2.81 X 9.3 = 26.1 kips < 33 N.G .

Which indicates 4 A325 bolts are not enough. Letus try 4 A490-N bolts:Rail = 2.81 X 12.4 = 34.8 kips > 33 O.K.Use: Four in. dia. A490-N bolts,

2. Calculate required gross area of plate:A^ g = R/OAOFyA^ g = 33/(0.40 X 36) = 2.29 in.Ûse A 36 steel an d select a plate satisfying the following

requirements:a. 4 ^^^ h l-5 i^.lh = K = 1.5 3/4) = 1.125 in.W = f l + 4 = 3 + 1.125 = 4.125 in.Use: W = 4V2 in.b. Lp/a > 2.0L^ = 3 + 3 X 3 = 12 in.Check: Lp/a = 12/3 = 4 > 2 O.K.c. tp < 4 / 2 + 1/16

tp < (y 4) /2 + 1/16 = yi6 in.d . tp = A^g ILptp = 2.29/12 = 0.19 in.

Use: PL 12xV4x4V2, A36 Steel.3. Calculate allowable shear strength of the net area:R,, =[Lp-n d, + Vi6)](g( 0 .3F jR^s = [12 - 4(3/4 + i/i6)](y4)(0.3 X 58) = 3 8.1 kipsR^s ^ ^ is satisfied.4. Calcu late actual allowable yield strength of the selectedplate:

R, = Lptp(0.40F,)Ro= llx 0.25 X 0.40 X 36 = 43.2 kipsDesign fillet welds for the combined effects of shearand moment:Shear = Ro = 43.2 kipse^ = Max

(n)(1.0) 4(1.0) = 4 in.= 3.0

Therefore, e^, 4.0 in.Moment = Rê = 43.2 x 4 = 172.8 kip-in.Using Table XIX AISC Manual^â = 4/12 = 0.33Ci = 1.0C = 1.07D16 = RJCCiLp = 43.2/(1.0 X 1.07 x 12) = 3.36Since weld size need not be greater than O.lStp,

Use: 3/16 in. E70 Fillet Welds.Check bearing capacity.For plate:ndf^tp (1.2FJ = 2.81 x .75 x .25 x 1.2 x 58= 36.7 kips > 33 kips,and for beam:ndi,t^{l.2F^) = 2.81 x .75 x .27 x 1.2 x 65

= 44.4 kips > 33 kips.Beam is not coped, therefore, no need for consideration of block shear failure.

CONCLUSIONSBased on the studies reported here, the following conclusions were reached:1. Th e experim ental studies of single plate connections in-

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dicated that considerable shear and bearing yieldingoccurred in the plate prior to the failure. The yieldingcaused reduction of the rotational stiffness which inturn caused release of the end moments to midspan ofthe beam.2. Th e limit states associated with single plate connectionsare:a. Plate yielding.b . Fractu re of net section of plate.c. Bolt fracture.d. Weld fracture.e. Bearing failure of bolt holes.3. A new design procedure for single plate shear connections is developed and recommended. The procedureis based on a concept that emphasizes facilitating shearand bearing yielding of the plate to reduce rotationalstiffness of the connection.

4. To avoid bearing fracture, the horizontal and verticaledge distance of the bolt holes are recommended to beat least 1.5 times diameter of the bolt. The study reported here indicated that vertical edge distance, particularly below the bottom bolt is the most critical edgedistance.

5. Single plate connections that were tested were veryductile and tolerated rotations from 0.026 to 0.061 radians at the poin t of maximum shear. Rotation al flexibility and ductility decreased with increase in number ofbolts.

ACKNOWLEDGMENTSThe project was supported by the Department of CivilEngineering, the University of California, Berkeley andthe American Institute of Steel Construction, Inc. Thesupport and constructive comments provided by R. O.Disque, N. Iwankiw and Dr. W. A. Thornton are sincerely appreciated. Single plates used in the test specimens were fabricated and supplied by the Cives SteelCompany. The assistance of R. Stephen, laboratory manager, in conducting the experiments was essential and isappreciated.

REFEREN ES1. Asta neh , A., Expe rimental Investigation of Tee-Framing Connection , Progress Report submitted to

Am erican Institute of Steel Construction, A pril 1987.2. Astane h, A., De man d and Supply of Ductility inSteel Shear Connections , Journal of Steel Construction Research, 1989.3. Asta neh, A. , K. M. McMullin, and S. M. Call, De sign of Single Plate Framing Connections, ReportNo. UCB/SEMM-88/12, De partm ent of Civil Engi

neering, University of California, Berkeley, July,1988.4. Asta neh , A ., and M. Nader, Design of Tee FramingShear Connect ions, Engineering Journal, AmericanInstitute of Steel Construction, First Quarter, 1989.5. Asta neh , A ., and M. Nader, Behavior and Design ofSteel Tee Framing Connections, Report No. UCBISEMM-88111,Department of Civil Engineering, University of California, Berkeley, July, 1988.6. Call, S. M ., and A . As tan eh, Behav ior of SinglePlate Shear C onnections with A325 and A490 Bolts ,Report No. UCB/SEMM-89/04, Department of CivilEngineering, University of California, Berkeley,April 1989.7. Iw ankiw, N. R., Design for Eccentric and InclinedLoads on Bolts and Weld Groups, Engineering Journal, American Institute of Steel Construction, 4thQuarter, 1987.8. L ipson, S. L., Single-Angle Welded-Bolted Connect ions , Journal of the Structural Division, March,1977.9. McMullin, K. M., and A. Astaneh, Analytical andExperimental Investigations of Double-Angle Connect ions , Report No. UCBISEMM-88114, Department of Civil Engineering, University of California,Berkeley, August, 1988.10. Patrick, M ., I. R. Thoma s, and I. D . Ben netts, Testing of the Web Side Plate Connection, AustralianWelding Research, December, 1986.

11 . Richard, R. M., P. E. Gillett, J. D. Kriegh, and B.A . Lewis, The Analysis and Design of Single PlateFraming Connec tions, Engineering Journal, American Institute of Steel Construction, 2nd Quarter,1980.12. W hite, R. N., Framing Connections for Square andRectangular Structural Tubing, Engineering Journal,American Institute of Steel Construction, July, 1965.13. American Institute of Steel Construction, Manual ofSteel Construction, 8th Edition, Chicago, 1980.14. American Institute of Steel Construction, Manual of

Steel Construction. LRFD, 1st Editio n, Chicago,1986.15. American Institute of Steel Construction, Inc.,Specification for the Design, Fabrication and Erection ofStructural Steel for Buildings, Chicago, November 13,1978.16. American Institute of Steel Construction, Inc., Loadand Resistance Factor Design Spe cification for Structural Steel Buildings, Chicago, September 1, 1986.



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AAygcCi

N OM E N C L A T U R ENet area in shear, in.Êffective net area of plate in shear, in.^Gross area of plate in shear, in^.Coefficient in the AISC Manual Tables X and XIXCoefficient in the AISC Manual Table XIXNumber of sixteenth of an inch in fillet weld sizeSpecified minimum tensile strength of steel, ksi

F^ y Allowable shear stress for plate in yielding =0.40F^, ksi

F^ u Allowable ultimate shear strength = 0.30F^, ksiFy Specified yield stress of steel, ksiL Length of span, in.Lp Length of plate, in.Mp Plastic moment capacity of cross section =Z^FyM y^bolt

RoR.

Y i e l d m o m e n t of be am cro ss sect ion , k ip- in .R e a c t i o n of the b e a mdue to serv ice load , k ipsA l l o w a b l e s h e a r c a p a c i t y of bol t g roupAl lo wable sh ear f r ac tu re cap ac i t yof the netsect ionAl lo wable sh ear y i e ld s t r en g th of p la te , k ipsR e a c t i o n c o r r e s p o n d i n g top last ic co l lapseof b e a m ,kips

Sx S e c t i on m o d u l u sin.^V Sh ear fo rce , k ip sW W i d t h of p l a t e , in.Zx P las t i c sec t i o n m o d u lu s ,in.â Coeff icien t in the A I S C M a n u a l T a b l eXIXa Di s t a n ce be tw een bo l t l i n e and weld l i n e ,in.d D e p t h of b e a m , in.dh D i a m e t e r of b o l t , in.e E c c e n t r i c i t y of p o i n t of inflection from the su p p o r te^ E c c e n t r i c i t y of be am re ac t i o n f ro m bo l t l i n e ,in.^w Eccen t r i c i t y of be am reac t i o n f ro m weld l i n e ,in.fyy C o m p u t e d s h e a r s t re s s in p l a t e g ro ss a rea ,ksifû C o m p u t e d s h e a r s t re s s in p late effect ive net a rea ,

ksiIh H o r i z o n t a l e d g e d i s t an c e of bo l t s ,in.l^ Ver t i ca l ed g e d i s t an ce of bo l t s ,in.n N u m b e r of bol tsr^ Al lo w ab le sh ear s t r en g thof onebol t , k ipstp T h i c k n e s s of p l a t e , in.ty^, Thickness of beam web, in.

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design of single plate shear connections

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