Deformation capacity of steel structures

Abstract In ultimate limit state design and seismic design, the formation of plastic hinges is assumed in the frame analysis, postulating an unlimited rotation capacity of structural members. However, the plastic deformation capacity of steel structural members with a stress gradient along their length is closely related to the stress-strain relationship of the steel, and if the yield ratio (the ratio of yield stress to tensile strength) of the steel is too high, one cannot expect any substantial plastic deformation. In this paper, the plastic deformation capacities of tension members, columns, beam-columns and beams are evaluated as functions of the yield ratio. For beam-columns and beams, the deformation capacities are evaluated more precisely in terms of the complementary energy of the steel. The deformation capacity of steel members subjected to local buckling is also discussed.