Overstrength and deformation 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, current version of European seismic code provides limited rules and guidance to evaluate the ductility as well as the plastic rotation capacity of HSS members. Within the framework of revision of Eurocodes, still in progress, the research activity carried out in this study is aimed at developing formulations to predict both deformation capacity and overstrength of cold formed HSS beams and columns. Therefore, parametric finite element simulations were carried out on a comprehensive set of members varying the shape of cross sections (i.e. both square and rectangular HSS), local and global slenderness, shear length and axial load. The adopted finite element models were calibrated against results of cyclic experimental tests available from existing literature. The results of the parametric analysis were processed in order to derive analytical equations predicting the overstrength factor and the deformation capacity at both significant damage and near collapse limit states.