AISC LRFD 1.pdf

16 PROPORTIONS OF BEAMS AND GIRDERS [Sect. B10.subject to the applicable provisions in Appendix G1, provided they are not requiredto resist an axial force greater than b times 0.15F yf A g , where F yf is the specifiedminimum yield stress of the flange material and A g is the gross area. No limit isplaced on the web stresses produced by the applied bending moment for which ahybrid girder is designed, except as provided in Section K3 and Appendix K3. Toqualify as hybrid girders, the flanges at any given section shall have the samecross-sectional area and be made of the same grade of steel.Flanges of welded beams or girders may be varied in thickness or width by splicinga series of plates or by the use of cover plates.The total cross-sectional area of cover plates of bolted or riveted girders shall notexceed 70 percent of the total flange area.High-strength bolts, rivets, or welds connecting flange to web, or cover plate toflange, shall be proportioned to resist the total horizontal shear resulting from thebending forces on the girder. The longitudinal distribution of these bolts, rivets, orintermittent welds shall be in proportion to the intensity of the shear. However, thelongitudinal spacing shall not exceed the maximum permitted for compression ortension members in Section E4 or D2, respectively. Bolts, rivets, or welds connectingflange to web shall also be proportioned to transmit to the web any loads applieddirectly to the flange, unless provision is made to transmit such loads by directbearing.Partial length cover plates shall be extended beyond the theoretical cutoff pointand the extended portion shall be attached to the beam or girder by high-strengthbolts in a slip-critical connection, rivets, or fillet welds. The attachment shall beadequate, at the applicable design strength given in Sections J2.2, J3.8, or K3 todevelop the cover plate’s portion of the flexural design strength in the beam orgirder at the theoretical cutoff point.For welded cover plates, the welds connecting the cover plate termination to thebeam or girder shall have continuous welds along both edges of the cover plate inthe length a, defined below, and shall be adequate, at the applicable designstrength, to develop the cover plate’s portion of the design strength in the beam orgirder at the distance a from the end of the cover plate.(a) When there is a continuous weld equal to or larger than three-fourths of theplate thickness across the end of the platea = w(B10-4)wherew = width of cover plate, in. (mm)(b) When there is a continuous weld smaller than three-fourths of the plate thicknessacross the end of the plate(c)a = 1.5wWhen there is no weld across the end of the platea =2w(B10-5)(B10-6)LRFD Specification for Structural Steel Buildings, December 27, 1999AMERICAN INSTITUTE OF STEEL CONSTRUCTION