AISC LRFD 1.pdf

27Chap. ECHAPTER ECOLUMNS AND OTHER COMPRESSION MEMBERSThis chapter applies to compact and non-compact prismatic members subject to axialcompression through the centroidal axis. For members subject to combined axial compressionand flexure, see Section H1.2. For members with slender compression elements,see Appendix B5.3. For tapered members, see Appendix F3.E1. EFFECTIVE LENGTH AND SLENDERNESS LIMITATIONS1. Effective LengthThe effective length factor K shall be determined in accordance with Section C2.2. Design by Plastic AnalysisDesign by plastic analysis, as limited in Section A5.1, is permitted if the columnslenderness parameter c does not exceed 1.5K.E2. DESIGN COMPRESSIVE STRENGTH FOR FLEXURAL BUCKLINGThe design strength for flexural buckling of compression members whose elementshave width-thickness ratios less than r from Section B5.1 is c P n :(a) For c 1.5 c = 0.85P n = A g F crλ c( . )Fcr = 0658 2(b) For c > 1.5Fcr= ⎡ 0877 .Fy⎣ ⎢ ⎤2λc⎦⎥whereλ c = Kl FyrπEA g = gross area of member, in. 2 (mm 2 )F y = specified minimum yield stress, ksi (MPa)E = modulus of elasticity, ksi (MPa)K = effective length factorl = laterally unbraced length of member, in. (mm)r = governing radius of gyration about the axis of buckling, in. (mm)LRFD Specification for Structural Steel Buildings, December 27, 1999AMERICAN INSTITUTE OF STEEL CONSTRUCTIONFy(E2-1)(E2-2)(E2-3)(E2-4)