Development and validation of fiber model for high-strength square concrete-filled steel tube beam-columns

Steel-concrete composite construction has become popular because it combines the advantages of both steel and concrete materials economically. This article presents a general fiber model that can be used to predict the monotonic and cyclic force-deformation behavior of high-strength square concrete-filled steel tube (CFT) beam-columns. The authors also present a general analytical approach for developing the critical input parameters for the fiber model, that is, the stress-strain curves for the fibers modeling the CFT cross section. Their general approach develops the fiber stress-strain curves analytically from the results of a three-dimensional nonlinear finite element analysis of a corresponding CFT segment. The authors report on the validation of their model with experimental data from 26 high-strength square CFT beam-column specimens that were tested under combined axial and monotonic or cyclic flexural loading. The results from the CFT fiber models compare reasonably accurately with the corresponding experimental results.