Plastic Rotation of Composite Beams

The sagging rotation capacity of composite beams consisting of a concrete slab attached to a steel beam by a shear connection is studied. Tests are reported on four full-scale beams in the range of ductility parameter x from 0.65 to 3.0. This parameter is an index of the degree of strain-hardening developed in the steel beam at collapse. Expressions are proposed for the minimum inelastic rotation and deflection available at collapse. Examples are given of the application of these expressions to design problems with continuous composite beams. It is shown that, with a minimum value of x equal to 1.4, sufficient sagging rotation should be available to develop the conventional plastic design collapse load under the worst combinations of spans and loading.