Performance of composite steel/concrete members under earthquake loading. Part I: Analytical model

This paper presents an advanced non‐linear model developed for the analysis of composite steel/concrete frame structures subjected to cyclic and dynamic loads. The formulation consists of beam‐column cubic finite elements accounting for geometric non‐linearities and material inelasticity. The non‐linear cyclic concrete model considers confinement effects and the constitutive relationship for steel includes the effect of local buckling and variable amplitude cyclic degradation. The model is calibrated and compared with experimental data from cyclic and pseudo‐dynamic tests conducted by the writers on a new ductile partially‐encased composite beam‐column. The accuracy and efficiency of the developed model are demonstrated through the correlation between the experimental results and analytical simulations. In a companion paper, the model is used to conduct parametric studies leading to important conclusions for ductility‐based earthquake‐resistant design.