Modeling of circular concrete-filled steel tubes subjected to cyclic lateral loading

In this paper, a simple and efficient yet fairly accurate analytical model for the cyclic behavior and strength capacity of circular concrete-filled steel tubes (CFT) under axial load and cyclically varying flexural loading is developed. Firstly, an accurate nonlinear finite element model is created using the ATENA software. The validity of this model is established by comparing its analyses results with those of experimental data published in the pertinent literature. Then, using this finite element model, an extensive parametric study is conducted to create a fairly broad databank of hysteretic behavior of circular CFTs, involving numerous circular CFT columns with different diameter to thickness ratios, steel tube yield stress and concrete strength. On the basis of this databank, empirical expressions are developed to evaluate the phenomenological parameters of the well-known Ramberg-Osgood hysteretic model. Additionally, empirical analytical relations providing a direct and efficient representation of the ultimate strength of circular CFT columns are constructed and validated. Comparisons between analytical and experimental results demonstrate that the proposed analytical model can describe efficiently and reliably the behavior of circular CFT columns under cyclic lateral loading.