Prediction of the cyclic rotation capacity of steel members with cold‐formed hollow cross‐section

Cold formed Hollow Structural Sections (HSS) are widely used in structural applications, especially in multi‐storey buildings located in seismic areas because of their high strength‐to‐weight ratio and torsional stiffness. However, the current version of the European seismic code provides limited rules and guidance to evaluate the ductility and the plastic rotation capacity of HSS members. The research activity carried out in this study aims to develop formulations to predict both the deformation capacity and the overstrength of cold formed HSS beams and columns at significant damage and near collapse limit states. Therefore, parametric finite element simulations have been carried out on a large set of members with different cross section (i.e., both square and rectangular HSSs), local and global slenderness, shear span and axial load ratio (from 0 to 0.5). The adopted finite element models have been calibrated against results of cyclic experimental tests available from the literature. The accuracy of the proposed equations has been statistically verified and discussion of practical applications is also provided.