Concrete-filled steel tubes subjected to axial compression: Life-cycle based performance

Abstract

This paper presents a life-cycle based finite element analysis modelling for concrete-filled steel tubular (CFST) stub columns. The effects of initial imperfections (e.g., residual stresses induced by cold forming or welding, and initial geometric imperfections), preloads during the construction process, long-term sustained loads and corrosion are considered in the modelling. To reveal the life-cycle time-dependent behaviour of CFST stub columns, influences of the above factors on the full-range load-displacement relations and the load-transfer mechanism are discussed in regard of five typical working conditions as: Case 0 - short-term loading; Case 1 - initial imperfection with short-term loading; Case 2 - initial imperfection, short-term loading followed by sustained load; Case 3 - initial imperfection, short-term loading followed by sustained load and corrosion; as well as Case 4 - initial imperfection, preload, short-term loading, sustained load and corrosion. Considering the effects of these factors, definition of the ultimate state of CFST stub columns under typical working conditions are discussed. Parametric studies are then carried out to calibrate the simplified design models for CFST stub columns at different loading cases. A database with information of 1096 CFST stub column specimens are established. Reliability analysis proves that the proposed simplified methods meet the reliability requirements in accordance with current design standards for CFST members under the five discussed cases. Partial factor for axial compressive strength of the composite section is suggested at the end of this paper.