Inelastic Steel Beams Under Uniform Moment

The out-of-plane behavior of closely braced steel wide-flange beams is examined. Unloading (failure) of such beams terminates their rotation capacity and thus their usefulness in plastic design. A theory of discontinuous yielding is used to estimate the out-of-plane behavior in the inelastic range and to provide an analytical prediction of the rotation capacity of beams under uniform moment. The lateral support spacing is found to be a function of the quantity of rotation which the beam is required to deliver. It is shown that the condition of the spans adjacent to the one under consideration has a marked influence on the behavior of the beam. The effective length concept is used to account for this effect.