Proposed Design Author Criteria for Stiffened Seated ... · engineering from The Citadel in 1982,...

Proposed DesignCriteria for

Stiffened SeatedConnections to

Column Webs

Duane S. Ellifritt

Thomas Sputo

AuthorSince 1984, Duane S. Ellifritt hasbeen Crom Professor of StructuralDesign in the Department of CivilEngineering at the University ofFlorida. He received a bachelor ofscience degree from Marshall col-lege, a master of science from theUniversity of Cincinnati, and aPh.D. from West Virginia Univer-sity.

Dr. Ellifritt previously worked asa product design engineer for theMetal Products Division of ArmcoSteel Corporation. He was assis-tant professor of civil engineering atOklahoma State University anddirector of engineering and re-search for the Metal BuildingManufacturers Association.

He is a professional member ofthe American Institute of Steel Con-struction, and a member of theAmerican Society of Civil En-gineers. He serves on the AISCCommittee on Specifications andthe AISI Advisory Group on theSpecifications of the Design ofCold-Formed Structural SteelMembers.Dr. Ellifritt is a registered profes-sional engineer.

AuthorThomas Sputo is a post-doctoralresearch assistant in the Depart-ment of Civil Engineering at theUniversity of Florida. He received abachelor of science in degree civilengineering from The Citadel in1982, and a master of engineeringdegree and Ph.D, both in structuralengineering, from the University ofFlorida in 1983 and 1990 respec-tively.

Between 1983 and 1987,Dr. Sputo served in a variety oftroop unit and staff positions as acommissioned officer in the UnitedStates Army Corps of Engineers.

He is a professional member ofthe American Institute of Steel Con-struction, and a member of both theAmerican Society of Civil En-gineers and the Society ofAmerican Military Engineers. Dr.Sputo is a registered professional

engineer in Virginia and Florida andis an active consulting structuralengineer.

SummaryIn multi-story braced frame con-struction, the connection of choicefor many fabricators for Type 2 orType PR connections betweenbeams and column webs is theseated connection. This connec-tion lends itself to ease of erectionbecause of its greater tolerancewhen compared to framing anglesor a "knife" connection. Becausethe beam may be cut short, insert-ing the beam between the columnflanges is a simpler procedure. Theadditional advantage of the seatproviding a stable erection platformfor the beam before bolts are in-stalled is an advantage for seatedconnections over framed connec-tions.

The strength and stability of thecolumn web supporting these con-nections has been questioned attimes, both by design engineersand code enforcement officials.

Research, sponsored by theAmerican Institute of Steel Con-struction, has been undertaken tostudy the behavior of this connec-tion, and to provide designguidance to designers anddetailers. Forty-seven connectionswere tested as part of a two yearstudy. A limit state for column webstrength has been noted as a resultof this testing.

Proposed design guidelines forboth Allowable Stress Design(ASD) and Load and ResistanceFactor Design (LRFD) for this con-nection have been developed.

8-1© 2003 by American Institute of Steel Construction, Inc. All rights reserved.

This publication or any part thereof must not be reproduced in any form without permission of the publisher.

PROPOSED DESIGN CRITERIA FOR STIFFENED SEATEDCONNECTIONS TO COLUMN WEBS

ByThomas Sputo and Duane S. Ellifritt

INTRODUCTION

In multistory frames, Type 2 or Type PR simpleconnections of beam to column web are often made by beamseats. Seated connections have advantages over framedconnections in that they possess larger erection andfabrication tolerance and provide a stable erection platformfor the beam before any bolts are installed.

The design of stiffened seated connections to columnwebs is an area where no definitive design guidance iscurrently available. This lack of guidance is acknowledgedin both manuals [1,2] in the connection design section bynoting that special connections must be designed forsupporting members (columns) with thin webs. The strengthand stability of the column web supporting these connectionshas been questioned by design engineers, fabricators, andcode enforcement officials.

A number of studies of a simpler, somewhat relatedsituation, that of a welded tab bracket on a column web havebeen undertaken [3,4,5,6,7,8], using a yield line analysisto model the column web behavior and determine the ultimateconnection strength. These studies, while helpful, are notdirectly applicable to the stiffened seat connection.

A two year research program was undertaken at theUniversity of Florida under the sponsorship of the AmericanInstitute of Steel Construction (AISC) to study the behaviorof this connection and to develop design guidelines for itssafe use.

BRIEF SUMMARY OF LABORATORY TESTING

Phase One Testing

Phase One testing consisted of 32 reduced scaleconnections. The intent of this phase was to study columnweb strength, observe column web/flange interaction, todetermine the interaction between column web bending andcolumn axial capacity, and to study the interaction betweenbeam curvature and column web out-of-plane deformations.

Full details of this testing are contained in a reportto AISC [10]. Some important conclusions were:

1. Contrary to concerns of some engineers, the bottomtip of the stiffener will not punch through the

8-3

© 2003 by American Institute of Steel Construction, Inc. All rights reserved.This publication or any part thereof must not be reproduced in any form without permission of the publisher.

column web. This was verified on webs as thin as1/8 inch.

2. The connection will rotate more than the beam,reducing the eccentricity of the applied load,thereby reducing the stress on the welds.

3. Yield line mechanism formation in the column webis a valid concern. While no connection failed inthis manner, the mechanism was observed formingprior to the failure of the column by weak-axiscolumn failure.

4. The rotation of the connection and the column webmakes this a very flexible connection,approximating a fully simple condition.

5. The flexibility of the connection, coupled withthe small eccentricity of the load makes itunnecessary to consider any eccentricity of loador applied moment in the design of the column.

Phase Two Testing

Phase Two testing consisted of 16 connections, 15 tocolumn webs, and one to a column flange as a baseline test.Column sections (W10X33,W12X40,W14X61) were chosen to berepresentative of normal column sections with relativelyslender webs.

The connection chosen had a stiffener length (L) of 8inches, a seat plate length (BS) of 6-1/2 inches, and astiffener width (W) of 6 inches. The erection bolts were7/8 inch A-325 bolts, placed 3 inches out from the columnweb face, installed snug-tight. While this connectionprobably would not be typically encountered, it was chosenas a "worst case situation" of a short stiffener lengthcombined with a wide stiffener width. Most usualconnections would not be this severe.

The beam was a welded girder of Grade 70 steel,proportioned to rotate similar to a realistically sized beamwhich might frame into one of the chosen test columns, whilebeing strong enough not to yield under the full capacity ofthe test equipment.

Failure loads and material properties are shown inTables 1 and 2. Full details of this testing are containedin a report to AISC [11].

The predominant mode of failure was weld shear, asshown in Figures 1 and 2. Weld failure began at the cornersof the seat, then rapidly spread, leading to total loss ofload capacity. It was assumed that this was because of astress concentration due to shear lag effects. Shear lag iscaused by the force in the seat plate and weld migratingtowards the stiffer column flanges. Test W14X61 TA-R hadstrain gauges installed on the seat. Figure 3 shows thestress gradient in the seat plate.



A yield line collapse mechanism was observed to beforming in the column web prior to failure of the welds.Evidence of the mechanism forming is shown in Figure 4.

DEVELOPMENT OF DESIGN PROCEDURES

Introduction

Based on the observed behavior of the test specimens,the following failure modes were established:

1. Weld shear failure2. Yield line failure of the column web

These design recommendations are applicable to columnswhich meet the following criteria:

1.2.

3.

The first criterion is derived from test results toensure that the effects of shear lag on the welds do notcause the values for weld strength listed in the Manual ofSteel Construction [1,2] to be rendered unconservative.This is shown in Figure 5.

The second criterion is empirical, based on the limitsof experimental testing of column sections of nominal depthof 14 inches or less. As no sections of greater depth weretested, no assurances as to their performance can be made.

The third criterion is also empirical, designed toensure that the column flanges are torsionally stiff enoughwith relation to the web to allow the yield line mechanismto proceed to failure, if the welds were not to fail firstin shear. This criterion is derived from a ratio of themoment of inertia of the web to the torsional stiffness ofthe flange.

Removing constants produces criterion three. Theuppermost limit for tested sections in Phase Two was 0.362for the W10X33. As this section did not produce excessiveflange rotations, and the more flexible sections of PhaseOne did, the limit of 0.362 was chosen.

These criteria allow the use of all standard columnsections: W14X43 - W14X730

W12X40 - W12X336W10X33 - W10X112W8X24 - W8X67W6X20 - W6X25W5X16 - W5X19

8-5


Weld Strength

The load tables in both LRFD and ASD editions of theManual of Steel Construction [1,2] are based on weldstrength with the load located at an eccentricity of 0.8times the stiffened width from the welds, or 0.8W. When theconnection is located on the web, the web rotates more thanthe beam end, thereby decreasing the effective eccentricityto a value of less than 0.30W, reducing to some extent thetheoretical weld stress.

But as previously noted, the stress in the seat plateis decidedly nonuniform due to shear lag effects.Therefore, the weld stress at the outside corners of theseat plate, where fracture is initiated, is magnified.These two actions of shear lag and decreased eccentricitytend to counterbalance themselves, rendering the existingweld tables somewhat conservative. Based on the limits oftesting, this assumption should not be extended to caseswhere the seat erection bolts are located more than 0.5times the stiffener width (0.50W) or 2-5/8 inches (greatervalue) out from the column web face.

Yield Line Analysis

It is a well known fact that the elastic limit is notthe true strength of a material such as steel which isductile and able to redistribute stresses. For example, theplastic moment capacity of a rectangular beam is 150 percentof the first yield moment of that same beam.

Ultimate strength analysis of plate structures whichprimarily resist load through flexure may be analysed by theyield line method. A yield line is a continuous plastichinge formed between two plate segments. The goal of yieldline analysis the same as that of plastic analysis of framedstructures, that is to determine an ultimate inelasticcollapse load. A complete discussion of the yield linemethod is beyond the scope of this paper and the reader isreferred to any reference on the topic. [12]

The least work collapse mechanism for a T-shaped seat,as shown in Figure 6, has been calculated [3] as:

Pu = k L m / e (1)

where:

Pu = Ultimate applied load

k = Yield line factor

= A [ B(C) + D + E ]

A = 2 / [2T-BS]

B = 2 + [0.866T/L]



BS = Seat plate length

L = Stiffener length

e = Eccentricity of applied load

m = Ultimate moment capacity of a unit width of plate

= F* t2 / 4F* = Limiting stress

t = Column web thickness

It must be noted that that the yield line method doesnot consider any factors other than bending, such as axialor shearing forces, membrane action, or the effects of largedeformations or strain hardening. The beneficial effect ofmembrane action and strain hardening has been taken intoaccount in various ways by different researchers. Onepossible method [9], which tended to provide reasonablyconservative results when compared to test data, is to use amodified ultimate stress value of:

F* = Fy + 2/3 (Fu - Fy) (2)

This modified stress value explicitly takes intoaccount the increased strength caused by strain hardening atlarge plate rotations, and implicitly considers the effectsof membrane strengthening of plates at large deflections.

PROPOSED DESIGN METHOD

Fabrication and Erection Criteria

The following design should be followed in fabricatingand erecting this connection.

1. Permanent high strength (A325 or A490) erectionbolts of no less than 3/4 inch should be used tosecure the beam to the seat. Welds should not beused as they lack the necessary ductility.

2. Erection bolts should be located no further fromthe column web face than the greater value of0.50W or 2-5/8 inch. This is shown in Figure 7.

3. Seat plate should not be welded to the columnflanges. To do so will negate this designprocedure and induce relatively large momentsinto the column cross section.



Weld Design

Welds should be designed from the applicable welddesign tables in the Manual of Steel Construction [1,2], andfabricated as shown in the accompanying manual figures, withthe exception of erection bolts substituted for erectionwelds.

Column Web Yielding

From the basic yield line equation, the two followingequations are suggested:

ASD (3)and

LRFD (4)where

Factored loadUnfactored loadStiffener lengthPlastic plate strength

tW2 F* /4Column web thicknessLoad eccentricity(B/2 + 1/4) inchesDistance from column web face to center oferection bolt

Fy + 2/3(Fu-Fy)0.90Yield line factor

The calculation of k can be somewhat complicated. Achart for the value of (k L) is provided in Table 3. Thechart assumes that the seat plate width (and length of weldbeneath the seat) is equal to 0.4L + 1/2 inch. The chart isslightly conservative for all possible larger seat widths.

REVISED DESIGN CHARTS FOR MANUAL OF STEEL CONSTRUCTION

Modifications to the design aids in the Manual of SteelConstruction were produced to allow direct selection ofconnections without resorting to calculation of the columnweb strength. The restrictions noted will ensure that weldfailure will occur before column web failure by yielding.The revised tables and charts are provided in an Appendix tothis paper.



SUMMARY AND CONCLUSIONS

Design criteria for stiffened seated connections tocolumn webs was presented. The procedure outlined is simpleand requires little change from present design, fabrication,and erection practice. The procedure recognizes two failuremodes and uses accepted engineering principles in theirsolution.

ACKNOWLEDGMENTS

Funding for this research was provided by the AmericanInstitute of Steel Construction, Inc.

Materials and services were donated by Owen SteelCompany of Florida, Jacksonville, Florida; SteelFabricators, Inc., Fort Lauderdale, Florida; and SheffieldSteel Products, Inc., Palatka, Florida.

The authors acknowledge the advice of Mr. David Ricker,Berlin Steel Construction Co., Dr. Thomas Murray, VirginiaPolytechnic Institute, the AISC Committee on Research, andthe AISC Committee on Manuals, Textbooks, and Codes.

REFERENCES

1. American Institute of Steel Construction, Manual ofSteel Construction, Load and Resistance FactorDesign, First Edition, AISC, Chicago, 1986.

2. American Institute of Steel Construction, Manual ofSteel Construction, Allowable Stress Design, NinthEdition, AISC, Chicago, 1989.

3. Abolitz, A. Leon and Marvin E. Warner, "Bending UnderSeated Connections." Engineering Journal, FirstQuarter, 1965, pp. 1-5.

4. Hoptay, Joseph M., "Ultimate Strength Capacity ofColumn Webs Subjected to Bracket Loading." M.S.Thesis, Clarkson College of Technology, Potsdam,NY, 1979.

5. Hoptay, Joseph M. and Heino Ainso, "An ExperimentalLook at Bracket Loaded Webs." EngineeringJournal, First Quarter, 1981, pp. 1-7.

6. Walsh, James J., "Determination of the Ultimate Loadfor Brackets Attached to Slender Column Webs."M.S. Thesis, Clarkson College of Technology,Potsdam, NY, 1980.



7. Hopper, Bruce E., "A Study of Welded Bracket to WebConnections." M.S. Thesis, Clarkson College ofTechnology, Potsdam, NY, 1983.

8. Hopper, Bruce E., Gordon E. Batson and Heino Ainso,"Bracket Loaded Webs With Low SlendernessRatios." Engineering Journal, First Quarter,1985, pp. 11-18.

9. Packer, Jeffery A. and T. Bruno, "Behavior of BoltedFlange Plate Connections in Rectangular HollowTension Members." Proceedings of the 10thAustralasian Conference on Mechanics of Structuresand Materials, 1986.

10. Ellifritt, Duane S. and Thomas Sputo, "Stiffened SeatedConnections to Column Webs, Phase One." Report tothe American Institute of Steel Construction.Department of Civil Engineering, University ofFlorida, 1989.

11. Ellifritt, Duane S. and Thomas Sputo, "Stiffened SeatedConnections to Column Webs, Phase Two." Report tothe American Institute of Steel Construction.Department of Civil Engineering, University ofFlorida, 1990.

12. Save, M.A. and C.E. Massonnet, Plastic Analysis andDesign of Plates, Shells, and Disks, Elsevier,New York, 1967.

EXAMPLE

Given:

8-10

Column - W12X40

Beam - W16X26

tw = 0.295 in.T = 9-1/2 in.Grade A-36 steel

DL = 5.75 kipsLL = 17.25 kipsTL = 23.00 kipsGrade A-36 steel


ASD Solution:1. Determine N

From Manual of Steel Construction (MSC)R1 = 15.8R2 = 5.94R3 = 15.0R4 = 1.77

N = (23.0-15.8)/5.94 = 1.21 inches= (23.0-15.0)/1.77 = 4.52 inches

Say N = 4-1/2 inchesSay W = 5 inches

2. Select SeatFrom MSC,

W = 5 in.L = 7 in.B = 2-5/8 in.Weld = 1/4 in.Load = 25.0 kips

NOTE: Yield line criteria need not be checked as thisconnection meets requirements of revised weld tables (seeAppendix).

3. Check Yield Line CriteriaB = 2-5/8 inchese = 2.625/2 + 0.25 = 1.56 in.From Table 3, (k L) = 98F* = 36 + 2/3(58-36) = 50.67 ksim = 0.25(.295)2(50.67) = 1.102 in-k

P = 0.60(98)(1.102)/1.56 = 41.5 kips41.5 > 23 OK

LRFD Solution:= 1.2(5.75) + 1.6(17.25) = 34.5 kips

1. Determine NFrom Manual of Steel Construction (MSC)

23.99.0022.52.65

N = (34.5-23.9)/9.00 = 1.18 inches= (34.5-22.5)/2.65 = 4.52 inches

Say N = 4-1/2 inchesSay W = 5 inches



2. Select SeatFrom MSC,

W = 5 in.L = 7 in.B = 2-5/8 in.Weld = 1/4 in.Load = 37.5 kips

NOTE: Yield line criteria need not be checked as thisconnection meets requirements of revised weld tables (seeAppendix).

3. Check Yield Line CriteriaB = 2-5/8 inchese = 2.625/2 + 0.25 = 1.56 in.From Table 3, (k L) = 98F* = 36 + 2/3(58-36) = 50.67 ksim = 0.25(.295)2(50.67) = 1.102 in-k

= 0.90(98)(1.102)/1.56 = 62.3 kips62.3 > 34.5 OK

Table 1. Phase Two Material Properties

Section Fy(ksi) Fu(ksi) F*(ksi)

W10X33

W12X40

W14X61

51.5

50.6

61.3

67.9

69.9

80.2

62.4

63.5

73.9

F* = Fy + 2/3 (Fu - Fy)

Note: Test coupons taken from the column webs



Table 2. Phase Two Test Results

W10X33 NAW12X40W14X61

W10X33W12X40W14X61

W10X33W12X40W14X61

W10X33W12X40W14X61

W10X33W12X40W14X61

W14X61

NANA

TATATA

TA-RTA-RTA-R

TA-WAATA-WAATA-WAA

TA-R-WTA-R-WTA-R-W

TA-FLA

146.6101.5105.3

95.580.5120.3

111.3112.048.9*

83.485.090.2

45.151.145.1

57.9

36.836.836.8

36.836.836.8

36.836.836.8

57.257.257.2

36.836.836.8

27.6

73.673.673.6

73.673.673.6

73.673.673.6

114.4114.4114.4

73.673.673.6

55.2

103.198.7177.4

103.198.7177.4

103.198.7177.4

103.198.7177.4

103.198.7177.4

N/A

1.991.381.43

1.301.091.63

1.511.52*

0.730.740.79

0.610.690.61

1.05

3.982.762.86

2.592.193.27

3.023.04>1.33

1.461.491.58

1.221.441.22

2.09

NATARWAAWFLA

= No erection angle installed= Top angle installed= Weld return of 1/2" on seat= Weld across both top and bottom of seat= Beam welded to seat in addition to erection bolts= Connection attached to flange rather than web

= ASD design load, kips

= Test failure load, kips

= Ultimate load based on weld strength, kips

= Ultimate load based on yield line strength, kips

1. All welds are 1/4" E70 fillet welds except forW14X61 TA-FLA, which was 3/16" fillet.

2. (*)Test terminated prior to failure due toequipment malfunction.

8-13

SECTION

Note:


Table 3. Values of k L

T

L 4 3/4" 6 1/8" 7 5/8" 9 1/2" 11" 11 1/4"

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

102

130

164

203

246

***

***

***

***

***

***

***

***

***

***

***

***

***

***

***

***

91

112

137

166

199

235

277

321

360

***

***

***

***

***

***

***

***

***

***

***

***

86

103

123

146

171

199

231

265

303

345

390

436

***

***

***

***

***

***

***

***

***

82

98

114

133

153

176

200

227

256

287

322

359

398

441

486

533

578

***

***

***

***

82

96

111

127

146

165

186

209

234

261

289

320

353

388

426

467

509

555

601

649

689

82

96

110

127

145

164

185

207

231

257

285

315

347

381

418

457

499

543

589

637

683



Figure 1. Column Web Rotation at Ultimate Load

8-15


Figure 2. Weld Fracture in Seat Plate

Figure 3. Shear Lag in Seat Plate

8-16


Figure 4. Development of Yield Line Mechanism

COLUMN WEB SLENDERNESS LIMIT

Figure 5. Column Web Slenderness Limit

8-17


8-18

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re 6.

Yiel

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re 7.

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APPENDIXSTIFFENED SEATED CONNECTION DESIGN AIDS

Revisions to the Stiffened Seated Beam Connectionsection of the ASD and LRFD Manual of SteelConstruction are noted here. Restrictions noted herewill ensure that weld failure will occur before columnweb failure by yield line analysis. Direct design ofstiffened seated connections to column webs istherefore possible without refering to other sources,except in the most extreme and rare cases.

Notes for Stiffened Seated Connections to Column Webs

1. Design criteria is applicable to the followingcolumn sections: W14X43 - W14X730

W12X40 - W12X336W10X33 - W10X112W8X24 - W8X67W6X20 - W6X25W5X16 - W5X19

2. Beam must be connected to seat by high-strengtherection bolts (A325 or A490). Centerline ofbolts are located no further from the column webface than the greater value of 0.50W or 2-5/8".Welding beam to seat plate is not recommended.

3. For seated connections where W=8" or W=9" and3-1/2" < B < 0.50W, or W=7" and 3" < B < 0.50W fora W14X43 column, see Sputo, Thomas and Duane S.Ellifritt, "Proposed Design Criteria for StiffenedSeated Connections to Column Webs," AISCEngineering Journal, Vol. ??, No. ?, ?th Quarter,199?.

4. Top angle is welded or bolted in place, 1/4"minimum thickness.

5. Seat plate should not be welded to column flanges.

6. Except as noted, maximum weld size is limited tocolumn web thickness (tW) for connections to oneside of the web. For connections in line onopposite sides of a column web, limit E70XX weldsize to 0.50tW for Fy=36ksi and 0.67tW forFy =50ksi.

8-19


STIFFENED SEATED BEAM CONNECTIONSWelded—E70XX electrodes

TABLE VIII

Seated connections should be used only when the beam is supported by a top angleplaced as shown above, or in the optional location as indicated.

Design loads in Table VIII are based on the use of E70XX electrodes. The tablemay be used for other electrodes, provided that the tabular values are adjusted for theelectrodes used (e.g., for E60XX electrodes, mult iply tabular values by 60/70 or0.86, etc.) and the welds and base metal meet the provisions of LRFD SpecificationSect. J2.

Design weld capacities in Table VIII are computed using traditional vectoranalysis.

Based on Fy = 36 ksi bracket material, minimum stiffener plate thickness, t, for

supported beams with unstiffened webs should not be less than the supported beamweb thickness for Fy = 36 ksi beams, and not less than 1.4 times the beam webthickness for beams with Fy = 50 ksi. Based on bracket material of Fy = 50 ksi orgreater, the min imum stiffener plate thickness t for supported beams with unstiffenedwebs should be the beam web thickness multiplied by the ratio of Fy of the beam to Fy ofthe bracket [e.g., Fy (beam) = 65 ksi; Fy (bracket) = 50 ksi: t = tw (beam) x 65/50,min imum] . The min imum stiffener plate thickness. t, should be at least two times therequired E70XX weld size when Fy of the bracket is 36 ksi, and should be at least 1.5times the required E70XX weld size when F

y of the bracket is 50 ksi.

Thickness t of the horizontal seat plate, or tee flange, should not be less than 3/8".If seat and st iffener are separate plates, finish stiffener to bear against seat. Welds

connecting the two plates should have a strength equal to, or greater than, thehorizontal welds to the support under the seat plate.

Welds at taching beam to seat may be replaced by bolts.ASTM A307 bolts may be used in seated connections, provided the stipulations of

LRFD Specification Sect. J1.9 are observed.For stiffener seats in l ine on opposite sides of a column web of Fy = 36 ksi

mater ia l , select E70XX weld size no greater than 0.50 of column web thickness. Forc o l u m n web of Fy = 50 ksi, select E70XX weld size no greater than 0.67 of column webthickness.

AMERICAN INSTITUTE OF STEEL CONSTRUCTION

LRFD MANUAL

8-20


STIFFENED SEATED BEAM CONNECTIONSWelded—E70XX electrodes

TABLE VIII Ultimate loads in kips

L,In.

6789

10

1112131415

1617181920

2122232425

2627

4

Weld Size, In.

34.044.956.769.282.3

95.8110124138152

167181196211225

240254269283297

312326

42.556.170.886.5

103

120137155173191

209227245263281

300318336354372

390408

51.167.385.0

104123

144165186207229

250272294316338

359381403425446

468489

59.678.699.2

121144

168192217242267

292318343369394

419445470495520

546571

Width of Seat W, in.

5

Weld Size, In.

35.246.959.873.788.5

104120137154171

189207225243261

279297315334352

370388

I

42.256.271.788.5

106

125144164185206

227248270291313

335357378400422

444466

49.365.683.7

103124

146168192216240

265290315340365

391416442467492

518543

56.375.095.6

118142

167192219246274

302331360388417

446476505534563

592621

6

Weld Size. In.

29.940.151.463.877.2

91.3106122138154

171188206223241

259277295313331

349368

35.948.161.776.692.6

110127146165185

205226247268289

311332354376397

419441- * —

41.956.172.089.3

108

128149170193216

240264288313337

362388413438464

489515

47.864.182.2

102123

146170195220247

274301329357386

414443472501530

559588

Connections to column webs

B 2-5/8" max

W12X40, W14X43 -

for L 9",

limit weld ¼"

2-5/8" max 3" max

Note: Loads shown are tor E70XX electrodes. For E60XX electrodes, multiply tabularloads by 0.86, or enter table with 1.17 times the given reaction. For E80XXelectrodes, multiply tabular loads by 1.14, or enter table with 0.875 timesthe given reaction.


LRFD MANUAL

8-21


STIFFENED SEATED BEAM CONNECTIONS

Welded—E70XX electrodes

TABLE VIII Ultimate loads in kips

L,In.

1112131415

1617181920

2122232425

2627282930

3132

Width of Seat W, In.

7

Weld Size, In.

81.094.7

109124139

155172188205223

240258275293311

329347365383402

420438

97.2114

131149167

186206225246267

288309330352373

395417438460482

504526

113133153174195

217240264287312

336361385410435

461486511537562

588613

130151174198223

249275301329356

384412440469498

526555584613643

672701

8

Weld Size, In.

72.585.198.3

112127

142157173189206

222240257274292

309327345363381

399417

87.1102118135152

170189208227247

267287308329350

371393414436457

479501

116136157180203

227251277303329

356383411439467

495524552581610

639668

145170197224253

283314346378411

445479514548584

619655690726762

799835

9

Weld Size. In.

65.677.189.3

102116

130144159175191

207223240257274

291308326344362

379397

78.792.5

107123139

156173191210229

248268288308329

349370391412434

455477

105123143164185

208231255280305

331357384411

438

466494522550578

607636

131154179204232

260289319350381

413446480513548

582617652687723

759795


B 3-1/2" max

W14X43, limit

B 3"See Note 3.

3-1/2" max

See Note 3.3-1/2" max

See Note 3.

Note: Loads shown are for E70XX electrodes. For E60XX electrodes, multiply tabularloads by 0.86. or enter table with 1.17 times the given reaction. For E80XXelectrodes, multiply tabular loads by 1.14, or enter table with 0.875 timesthe given reaction.


LRFD MANUAL

8-22


STIFFENED SEATED BEAM CONNECTIONSWelded-E70XX Electrodes

TABLE VIII

Seated connections should be used only when the beam is supported by a top angleplaced as shown above, or in the optional location as indicated.

Allowable loads in Table VIII are based on the use of E70XX electrodes. Thetable may be used for other electrodes, provided the tabular values are adjusted forthe electrodes used (e.g., for E60XX electrodes, multiply tabular values by , or0.86, etc.) and the welds and base metal meet the provisions of AISC ASD Specifica-tion Sect. J2.4.

Allowable weld capacities in Table VIII are computed using traditional vectoranalysis.

Based on Fy = 36 ksi bracket material, minimum stiffener plate thickness, t, forsupported beams with unstiffened webs should not be less than the supported beamweb thickness for Fy = 36 ksi beams, and not less than 1.4 times the beam web thick-ness for beams with Fy = 50 ksi. Based on bracket material of Fy = 50 ksi or greater,the minimum stiffener plate thickness, t, for supported beams with unstiffened websshould be the beam web thickness multiplied by the ratio of Fy of the beam to Fy ofthe bracket (e.g., Fy (beam) = 65 ksi; Fy (bracket) = 50 ksi; t = tw (beam) x 65/50,minimum). The minimum stiffener plate thickness, t, should be at least two times therequired E70XX weld size when Fy of the bracket is 36 ksi, and should be at least 1.5times the required E70XX weld size when Fy of the bracket is 50 ksi.

Thickness t of the horizontal seat plate, or tee flange, should not be less thanin.

If seat and stiffener are separate plates, finish stiffener to bear against seat.Welds connecting the two plates should have a strength equal to, or greater than, thehorizontal welds to the support under the seat plate.

Welds attaching beam to seat may be replaced by bolts.ASTM A307 bolts may be used in seated connections, if the stipulations of

AISC ASD Specification Sect. J1.12 are observed.


ASD MANUAL

8-23


Should combinations of material thickness and weld size selected from TableVIII exceed the limits set by AISC ASD Specification Sects. J2.2 and J2.4, increasethe weld size or material thickness as required.

In addition to the welds shown, temporary erection bolts may be used to attachbeams to seats (optional).

To permit selection of the most economical connection, the reaction valuesshould be given on the contract drawings. If the reaction values are not given, theconnections must be selected to support the beam end reaction calculated from theAllowable Uniform Load Tables for the given shape, span, and steel specification ofthe beam in question. The effect of concentrated loads near an end connection mustalso be considered.

EXAMPLE 19

Given:

Beam: W 30 × 116 (flange = 10.495 in. × 0.85 in.; web = 0.565 in.)ASTM A36 steel (Fy = 36 ksi)

Welds: E70XXReaction: 100 kips

Design a two-plate welded stiffener seat using ASTM A36 steel.

Solution:

From the Fy = 36 ksi, Allowable Uniform Load Table for W30 x 116, note that R1,= 54.5 kips, R2 = 13.4 kips/in., R3 = 79.9 kips, R4 = 4.33 kips/in.

For yielding N, req'd = (R - R1)/R2= (100 - 54.5)/13.4 = 3.40 in.

For buckling N, req'd = (R - R3)/R4= (100 - 79.9)/4.33 = 4.64 in.

Stiffener width = 4.64 + 0.5 (setback) = 5.14 in.

Use W = 6 in.

Enter Table VIII with W = 6 in. and a reaction of 100 kips; select a -in. weld withL = 15 in., which has a capacity of 103 kips. From this, the minimum length of weldbetween seat plate and support is 2 x 0.2L = 6 in. This also establishes the minimumweld between the seat plate and the stiffener as 6 in. total, or 3 in. on each side ofstiffener.

Stiffener plate thickness t to develop welds is 2 x = in., or 0.625 in. This isgreater than the beam web thickness of 0.565 in.; thus, the stiffener plate thicknessneed not be increased.

Use: -in. plate for the stiffener and -in. plate for seat.


ASD MANUAL

8-24




TABLE VIII Allowable loads in kips

L

In.

6789

10

1112131415

1617181920

2122232425

2627

Width of Seat W, In.

4

Weld Size, In.

17.022.428.334.641.1

47.954.861.969.076.2

83.590.798.0

105112

119127134141148

155163

22.729.937.846.154.9

63.973.182.592.0

101

111121131140150

160169179189198

208217

28.437.447.257.668.6

79.891.4

103115127

139151163175188

200212224236248

260272

34.044.956.769.282.3

95.8110124138152

167181196211225

240254269283297

312326

39.752.466.180.796.0

112128144161178

195212229246263

280296313330347

364380

5

Weld Size, In.

14.118.723.929.535.4

41.648.154.861.668.5

75.682.789.997.1

104

111118126133140

148155

18.825.031.939.347.2

55.564.173.082.191.4

100110119129139

148158168177187

197206

23.531.239.849.159.0

69.480.291.3

103114

126138150162174

189198210222234

247259

28.137.547.859.070.8

83.396.2

110123137

151165180194209

223238252267281

296310

32.843.755,868.882.6

97.1112128144160

176193210227243

260277294311328

345362

37.550.063.778.694.4

111128146164183

202221240259278

298317336356375

394414

6

Weld Size, In.

19.926.734.342.551.4

60.970.881.191.9

103

115126137149161

173185197209221

233245

23.932.041.151.161.7

73.185.097.4

110123

138151164179193

207221236250265

279294

27.937.348.059.672.0

85.299.2

114129144

160176192208225

242258275292309

326343

31.942.754.868.182.3

97.4113130147165

183201219238257

276295315334353

373392


B 2-5/8" max

W12X40,W14X43 -

for L 9",

limit weld ¼"

2-5/8" max 3" max

Note: Loads shown are for E70XX electrodes. For E60XX electrodes, multiply tabular loadsby 0.86, or enter table with 1.17 times the given reaction. For E80XX electrodes, multi-ply tabular loads by 1.14 or enter table with 0.875 times the given reaction.

AMERICAN INSTITUTE or STEEL CONSTRUCTION

ASD MANUAL

8-25




TABLE VIII Allowable loads in kips

L

in.

1112131415

1617181920

2122232425

2627282930

3132

Width of Seat W. In.

7

Weld Size, in.

54.063.172.782.692.9

104114126137148

160172183195207

219231243256268

280292

64.875.787.299.1

112

124137151164178

192206220234249

263278292307321

336350

75.688.4

102116130

145160176192208

224240257274290

307324341358375

392409

86.3101117132149

166183201219237

256274293312331

351370389409428

447467

8

Weld Size, in.

48.456.765.574.884.4

94.4105115126137

148159171183195

206218230242254

266278

58.068.178.789.8

101

113126138151165

178192205219233

248262276291305

319334

77.390.7

105120135

151167184202219

237255274292311

330349368387406

426445

96.6113131149169

189209230252274

296319342365389

412436460484508

532556


B 3-1/2" max

W14X43, limit

B 3"

See Note 3.

3-1/2" max

See Note 3.

9

Weld Size, in.

43.751.459.668.277.2

86.596.2

106117127

138149160171182

194206217229241

253265

52.461.771.581.892.6

104115127140152

165178192205219

233247261275289

303318

69.982.295.3

109123

138154170186203

220238256274292

310329348367386

405424

87.4103119136154

173192212233254

276297320342365

388411435458482

506530

3-1/2" max

See Note 3.

Note: Loads shown are for E70XX electrodes. For E60XX electrodes, multiply tabular loadsby 0.86, or enter table with 1.17 times the given reaction. For E80XX electrodes, multi-ply tabular loads by 1.14 or enter table with 0.875 times the given reaction.


ASD MANUAL



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