Steel-concrete composite structures with concrete-filled steel tube (CFT) columns are an excellent candidate for fire resistant design due to their enhanced fire resistance resulting from the presence of concrete. Researchers at the National Research Council of Canada have conducted significant research on the fire resistance of CFT columns. However, these studies were firmly rooted in the current prescriptive fire-resistant design philosophy. Currently, there is a significant lack of knowledge of the fundamental force-deformation behavior of CFT beam-columns subjected to elevated temperatures due to fire loading. Knowledge of this force-deformation behavior will lead to performance-based guidelines for designing fire-resistant composite structures with CFT columns. The proposed research project provides experimental and analytical investigations in two areas: (1) the fundamental force-deformation behavior and (2) the influence of various material (steel yield stress and concrete strength) and geometric parameters (tube width and b/t ratio) on the behavior of CFT beam-columns subjected to elevated temperatures from fire loading. The experimental investigations will be conducted on large-scale CFT specimens using an innovative and specially designed test method. The analytical investigations will involve the development and validation of 3D finite element models for the thermal and structural (mechanics) behavior of CFT specimens under fire loading. The validated models will be used to conduct analytical parametric studies. The results from the experimental and analytical studies will be used to calibrate a macro fiber-based finite element for modeling CFTs that can be used to investigate the structural behavior of CFT frames under fire loading.
