AISC LRFD 1.pdf

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Sect. B10.] PROPORTIONS OF BEAMS AND GIRDERS 132. Design by Plastic AnalysisDesign by plastic analysis is permitted, as limited in Section A5.1, when flangessubject to compression involving hinge rotation and all webs have awidth-thickness ratio less than or equal to the limiting p from Table B5.1. For circularhollow sections see Footnote d of Table B5.1.3. Slender-Element Compression SectionsFor the flexural design of I-shaped sections, channels and rectangular or circular sectionswith slender flange elements, see Appendix F1. For other shapes in flexure ormembers in axial compression that have slender compression elements, see AppendixB5.3. For plate girders with slender web elements, see Appendix G.B6. BRACING AT SUPPORTSAt points of support for beams, girders and trusses, restraint against rotation abouttheir longitudinal axis shall be provided.B7. LIMITING SLENDERNESS RATIOSFor members in which the design is based on compression, the slenderness ratioKl/r preferably should not exceed 200.For members in which the design is based on tension, the slenderness ratio l/rpreferablyshould not exceed 300. The above limitation does not apply to rods in tension.Members in which the design is dictated by tension loading, but which may besubject to some compression under other load conditions, need not satisfy the compressionslenderness limit.B8. SIMPLE SPANSBeams, girders and trusses designed on the basis of simple spans shall have aneffective length equal to the distance between centers of gravity of the members towhich they deliver their end reactions.B9. END RESTRAINTBeams, girders, and trusses designed on the assumptions of full or partial endrestraint, as well as the sections of the members to which they connect, shall havedesign strengths, as prescribed in Chapters D through K, equal to or exceeding theeffect of factored forces and moments except that some inelastic but self-limitingdeformation of a part of the connection is permitted.B10. PROPORTIONS OF BEAMS AND GIRDERSWhen rolled or welded shapes, plate girders and cover-plated beams are proportionedon the basis of flexural strength of the gross section:(a) If0.75F u A fn 0.9F y A fg (B10-1)no deduction shall be made for bolt or rivet holes in either flange,where<strong>LRFD</strong> Specification for Structural Steel Buildings, December 27, 1999AMERICAN INSTITUTE OF STEEL CONSTRUCTION
14 PROPORTIONS OF BEAMS AND GIRDERS [Sect. B10.TABLE B5.1Limiting Width-Thickness Ratios forCompression ElementsDescription of ElementWidthThicknessRatio p(compact)Limiting Width-Thickness Ratios r(noncompact)Flanges of I-shaped rolledbeams and channels inflexureb / t 038 . E / F y [c] 083 . E / F L [e]Unstiffened ElementsFlanges of I-shaped hybrid orwelded beams in flexureFlanges projecting frombuilt-up compressionmembersFlanges of I-shaped sectionsin pure compression, platesprojecting from compressionelements; outstanding legs ofpairs of angles in continuouscontact; flanges of channelsin pure compressionb / t 038 . E / F yf 095 . E /( FL / kc ) [e],[f]b / t NA 064 . E /( F / k )b / t NA 056 . E /y c [f]F yLegs of single angle struts;legs of double angle strutswith separators; unstiffenedelements, i.e., supportedalong one edgeb / t NA 045 . E /F yStems of tees d / t NA 075 . E /F yA fg = gross flange area, in. 2 (mm 2 )A fn = net tension flange area calculated in accordance with the provisions ofSections B1 and B2, in. 2 (mm 2 )F u = specified minimum tensile strength, ksi (MPa)(b) If0.75F u A fn < 0.9F y A fg (B10-2)the member flexural properties shall be based on an effective tension flange areaA fe5 FuA (B10-3)fe= Afn6 Fyand the maximum flexural strength shall be based on the elastic section modulus.Hybrid girders shall be proportioned by the flexural strength of their gross section,<strong>LRFD</strong> Specification for Structural Steel Buildings, December 27, 1999AMERICAN INSTITUTE OF STEEL CONSTRUCTION
Page 1 and 2: LOAD AND RESISTANCEFACTOR DESIGNSPE
Page 3: iiCopyright © 2000byAmerican Insti
Page 6 and 7: vTABLE OF CONTENTSSYMBOLS . . . . .
Page 8 and 9: TABLE OF CONTENTSviiSPECIFICATION (
Page 10 and 11: TABLE OF CONTENTSixSPECIFICATION (C
Page 12 and 13: TABLE OF CONTENTSxiCOMMENTARY (Cont
Page 18 and 19: SYMBOLSxviistrength (for those stee
Page 20 and 21: SYMBOLSxixS eff Effective section m
Page 22 and 23: SYMBOLSxxit s Web stiffener thickne
Page 24 and 25: xxiiiGLOSSARYAlignment chart for co
Page 26 and 27: GLOSSARYxxvEffective moment of iner
Page 28 and 29: GLOSSARYxxviiLateral bracing member
Page 30 and 31: GLOSSARYxxixPost-buckling strength.
Page 32 and 33: GLOSSARYxxxiStrain-hardening strain
Page 34 and 35: 1CHAPTER AGENERAL PROVISIONSA1. SCO
Page 36 and 37: Sect. A3.] MATERIAL 3Cold-Formed We
Page 38 and 39: Sect. A3.] MATERIAL 5ASTM A449 bolt
Page 40 and 41: Sect. A6.] REFERENCED CODES AND STA
Page 42 and 43: Sect. A7.] DESIGN DOCUMENTS 9tion A
Page 44 and 45: Sect. B4.] STABILITY 11(a) When the
Page 48 and 49: Sect. B10.] PROPORTIONS OF BEAMS AN
Page 50 and 51: 17Chap. CCHAPTER CFRAMES AND OTHER
Page 52 and 53: Sect. C3.] STABILITY BRACING 19all
Page 54 and 55: Sect. C3.] STABILITY BRACING 214. B
Page 56 and 57: Sect. C3.] STABILITY BRACING 231.0;
Page 58 and 59: Sect. D3.] PIN-CONNECTED MEMBERS AN
Page 60 and 61: 27Chap. ECHAPTER ECOLUMNS AND OTHER
Page 62 and 63: Sect. E4.] BUILT-UP MEMBERS 29(a) F
Page 64 and 65: 31Chap. FCHAPTER FBEAMS AND OTHER F
Page 66 and 67: Sect. F1.] DESIGN FOR FLEXURE 33Lp=
Page 68 and 69: Sect. F2.] DESIGN FOR SHEAR 35Lpd
Page 70 and 71: 37Chap. GCHAPTER GPLATE GIRDERSI-sh
Page 72 and 73: Sect. H3.] ALTERNATIVE INTERACTION
Page 74 and 75: Sect. I2.] COMPRESSION MEMBERS 41ti
Page 76 and 77: Sect. I3.] FLEXURAL MEMBERS 434. Lo
Page 78 and 79: Sect. I3.] FLEXURAL MEMBERS 45welde
Page 80 and 81: Sect. I5.] SHEAR CONNECTORS 47A c =
Page 82 and 83: 49Chap. JCHAPTER JCONNECTIONS, JOIN
Page 84 and 85: Sect. J1.] GENERAL PROVISIONS 518.
Page 86 and 87: Sect. J2.] WELDS 53Welding ProcessT
Page 88 and 89: Sect. J2.] WELDS 55For end-loaded f
Page 90 and 91: Sect. J2.] WELDS 57Types of Weld an
Page 92 and 93: Sect. J3.] BOLTS AND THREADED PARTS
Page 94 and 95: Sect. J3.] BOLTS AND THREADED PARTS
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Sect. J3.] BOLTS AND THREADED PARTS
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Sect. J3.] BOLTS AND THREADED PARTS
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Sect. J4.] DESIGN RUPTURE STRENGTH
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Sect. J8.] BEARING STRENGTH 69J6. F
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71Chap. KCHAPTER KCONCENTRATED FORC
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Sect. K1.] FLANGES AND WEBS WITH CO
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For P u 0.4P yR v = 0.60F y d c t
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Sect. K3.] DESIGN FOR CYCLIC LOADIN
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79Chap. LCHAPTER LSERVICEABILITY DE
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81Chap. MCHAPTER MFABRICATION, EREC
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Sect. M4.] ERECTION 83(2) Bottom su
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Sect. M5.] QUALITY CONTROL 85The fa
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Sect. N3.] EVALUATION BY STRUCTURAL
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89App. BAPPENDIX BDESIGN REQUIREMEN
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App. B5.] LOCAL BUCKLING 914kc=h/tw
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App. B5.] LOCAL BUCKLING 93é0.877
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App. E3.] DESIGN COMPRESSIVE STRENG
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App. F1.] DESIGN FOR FLEXURE 97For
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App. F1.] DESIGN FOR FLEXURE 99TABL
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App. F1.] DESIGN FOR FLEXURE 101Cri
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App. F3.] WEB-TAPERED MEMBERS 103j
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App. F3.] WEB-TAPERED MEMBERS 105Fw
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107App. GAPPENDIX GPLATE GIRDERSThi
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App. G3.] DESIGN SHEAR STRENGTH 109
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App. G5.] FLEXURE-SHEAR INTERACTION
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App. H3.] ALTERNATIVE INTERACTION E
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115App. JAPPENDIX JCONNECTIONS, JOI
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App. J3.] BOLTS AND THREADED PARTS
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App. K2.] PONDING 119æçMetric:lC
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App. K3.] DESIGN FOR CYCLIC LOADING
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NUMERICAL VALUES 141TABLE 2ItemShap
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NUMERICAL VALUES 143Klr123456789101
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NUMERICAL VALUES 145TABLE 3-50Desig
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NUMERICAL VALUES 147TABLE 4Values o
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NUMERICAL VALUES 149TABLE 5 (cont
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NUMERICAL VALUES 151TABLE 7Values o
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NUMERICAL VALUES 153f vVAwnTABLE 8-
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NUMERICAL VALUES 157hf vVAwnTABLE 9
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NUMERICAL VALUES 161ht wf vVAwnTABL
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163COMMENTARYon the Load and Resist
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Comm. A2.] TYPES OF CONSTRUCTION 16
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Comm. A3.] MATERIAL 167and Chen, 19
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Comm. A3.] MATERIAL 169than the ant
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Comm. A4.] LOADS AND LOAD COMBINATI
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Comm. A5.] DESIGN BASIS 173where =
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Comm. A5.] DESIGN BASIS 175( )bsln(
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177Comm. BCHAPTER BDESIGN REQUIREME
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Comm. B5.] LOCAL BUCKLING 179(c) Al
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Comm. B5.] LOCAL BUCKLING 181load.
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Comm. B7.] LIMITING SLENDERNESS RAT
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Comm. C1.] SECOND ORDER EFFECTS 185
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Comm. C1.] SECOND ORDER EFFECTS 187
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Comm. C2.] FRAME STABILITY 189Buckl
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Comm. C2.] FRAME STABILITY 191Notes
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Comm. C2.] FRAME STABILITY 193Where
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Comm. C3.] STABILITY BRACING 195age
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Comm. C3.] STABILITY BRACING 197pla
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Comm. C3.] STABILITY BRACING 199The
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Comm. C3.] STABILITY BRACING 201Par
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203Comm. ECHAPTER ECOLUMNS AND OTHE
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Comm. E4.] BUILT-UP MEMBERS 205TABL
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Comm. F1.] DESIGN FOR FLEXURE 207ha
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Comm. F1.] DESIGN FOR FLEXURE 2092b
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Comm. F4.] BEAMS AND GIRDERS WITH W
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Comm. H2.] UNSYMMETRIC MEMBERS AND
Page 248 and 249:
Comm. I2.] COMPRESSION MEMBERS 215d
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Comm. I3.] FLEXURAL MEMBERS 217may
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Comm. I3.] FLEXURAL MEMBERS 219The
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Comm. I3.] FLEXURAL MEMBERS 221wher
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Comm. I3.] FLEXURAL MEMBERS 223proc
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Comm. I4.] COMBINED COMPRESSION AND
Page 260 and 261:
Comm. I5.] SHEAR CONNECTORS 227tal
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229Comm. JCHAPTER JCONNECTIONS, JOI
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Comm. J1.] GENERAL PROVISIONS 231 P
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Comm. J2.] WELDS 2332b. Limitations
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Comm. J2.] WELDS 235When longitudin
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Comm. J2.] WELDS 237due to cyclic f
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Comm. J2.] WELDS 239(b) Plane 2-2,
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Comm. J3.] BOLTS AND THREADED PARTS
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Page 278 and 279:
Page 280 and 281:
Comm. J4.] DESIGN RUPTURE STRENGTH
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249Comm. KCHAPTER KCONCENTRATED FOR
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Comm. K1.] FLANGES AND WEBS WITH CO
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Comm. K1.] FLANGES AND WEBS WITH CO
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Comm. K2.] PONDING 255Even on the b
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257Comm. LCHAPTER LSERVICEABILITY D
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Comm. L5.] CORROSION 259orthotropic
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Comm. M4.] ERECTION 261It is sugges
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Comm. N4.] EVALUATION BY LOAD TESTS
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Comm. N5.] EVALUATION REPORT 265N5.
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267Comm. A-EAPPENDIX ECOLUMNS AND O
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Comm. App. F3.] WEB-TAPERED MEMBERS
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271Comm. A-GAPPENDIX GPLATE GIRDERS
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273Comm. A-KAPPENDIX JCONNECTIONS,
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Comm. J2.] WELDS 275found to be con
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Comm. K3.] DESIGN FOR CYCLIC LOADIN
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279ReferencesAckroyd, M. H., and Ge
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REFERENCES 281Bjorhovde, R. (1972),
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REFERENCES 283Fielding, D. J., and
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REFERENCES 285Johnson, D. L. (1985)
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REFERENCES 287Ollgaard, J. G., Slut
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REFERENCES 289Zhou, S. P., and Chen
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SUPPLEMENTARY BIBLIOGRAPHY 291Kotec
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Metric Conversion Factors for Commo
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