Technical Note: Optimum Flexural Design of Steel Members Utilizing Moment Gradient and Cb

Abstract

Flexural strength of members based on the limit state of lateral-torsional buckling is a function of the moment gradient of the unbraced length under consideration. Bending modification factor, Cb, accounts for the shape of the moment gradient within the unbraced length and allows for adjustment of the member flexural strength, possibly increasing it by a considerable amount. Therefore, neglecting the impact of Cb on member strength may lead to over-design. This paper discusses application of Cb to design of members subjected to bending including beams as well as members subjected to combined loading (compression and bending, tension and bending, or biaxial bending). Numerical examples are presented using both ASD and LRFD methods.