Fast Design of Beams with Cb Greater Than 1.0

The allowable flexural stress for steel beams with less than full lateral support is given by AISC Eqs. (1.5-6a), (1.5- 6b), or (1.5-7). Each of these equations contain the term Cb , a coefficient dependent upon the moment gradient. In Part 2 of the AISC Manual are curves for beams with allowable moment plotted for varying unsupported lengths. The curves are for Cb = 1.0. The following procedure affords a fast selection of a beam using the beam curves when the value of Cb is other than 1.0. A considerable saving of steel can result.