AISC LRFD 1.pdf

Sect. F2.] DESIGN FOR SHEAR 35Lpd⎡ ⎛ M ⎞ E= 0.12 + 0.076⎤⎛ ⎜ ⎟⎞r1⎢ ⎜ ⎟⎥yM ⎜2F ⎟⎣ ⎝ ⎠⎦⎝ y ⎠(F1-17)whereF y = specified minimum yield stress of the compression flange, ksi (MPa)M 1 = smaller moment at end of unbraced length of beam, kip-in. (N-mm)M 2 = larger moment at end of unbraced length of beam, kip-in. (N-mm)r y = radius of gyration about minor axis, in. (mm)(M 1 /M 2 ) is positive when moments cause reverse curvature and negative forsingle curvature(b) For solid rectangular bars and symmetric box beams:⎡ ⎛ M ⎞⎤⎛ ⎞ ⎛ ⎞1E ELpd = ⎢0.17 + 0.10⎜ ⎟⎥⎜ r ≥ ⎜ ⎟y0.10⎜ r ⎟y⎣ ⎝M2⎠⎦⎝Fy⎠ ⎝Fy⎠(F1-18)There is no limit on L b for members with circular or square cross sections nor forany beam bent about its minor axis.In the region of the last hinge to form, and in regions not adjacent to a plastic hinge,the flexural design strength shall be determined in accordance with Section F1.2.F2. DESIGN FOR SHEARThis section applies to unstiffened webs of singly or doubly symmetric beams,including hybrid beams, and channels subject to shear in the plane of the web. Forthe design shear strength of webs with stiffeners, see Appendix F2 or Appendix G3.For shear in the weak direction of the shapes above, pipes, and unsymmetric sections,see Section H2. For web panels subject to high shear, see Section K1.7. Forshear strength at connections, see Sections J4 and J5.1. Web Area DeterminationThe web area A w shall be taken as the overall depth d times the web thickness t w .2. Design Shear StrengthThe design shear strength of unstiffened webs, with h / t w 260, is v V n ,where v = 0.90V n = nominal shear strength defined as follows.(a) For h / t w 245 . E/F ywV n = 0.6F yw A w (F2-1)(b) For 245 . E/F yw < h / t w 307 . E/F ywLRFD Specification for Structural Steel Buildings, December 27, 1999AMERICAN INSTITUTE OF STEEL CONSTRUCTION