Simulation of inelastic cyclic behaviour of steel concentric bracings

The modelling of non-linear cyclic response of conventional concentric braces is a crucial aspect when seismic analyses have to be carried out to assess the capacity of steel braced structures under seismic events, becoming an urgent need in case of catastrophic earthquakes. In those cases the "exact" evaluation of brace ductility demand is essential to get the structural response in a reasonable manner. With the aim to provide effective and useful modelling tool, a numerical study is presented in this paper. The study is devoted to examine and validate the capability of physical-theoretic brace models implemented using available features of the nonlinear finite element based software "SEISMOSTRUCT". The nonlinear cyclic axial force-deformation simulations were performed for braces made of steel hot-rolled wide-flange and cold-formed tubular sections. The developed nonlinear brace model is verified using available test results from the literature. The results are in excellent agreement to those given by experimental tests in terms of accuracy of the shapes of hysteresis loops. In addition, for what concerns the computational effort the proposed model is satisfactory for seismic analysis and design purposes in practice.