Effect of stiffeners on the eccentric compression behaviour of square concrete-filled steel tubular columns

摘要

Concrete-filled steel tubular (CFST) structures are extensively used in engineering applications in China owing to their high strength and section modulus, ease of construction, and good seismic performance. However, the steel tubes of CFST members are prone to outward buckling under compression loads. Welding longitudinal stiffeners on these steel tubes is one of the most efficient approaches used for delaying the local buckling and improving the mechanical performance of CFST members. This study attempted to investigate the eccentric compression behaviour of concrete-filled stiffened steel tubular members with square sections by experimental studies and finite element analysis (FEA). First, 12 CFST columns with different slenderness ratios and loading eccentricities were subjected to compression loads and tested. It was found that the use of stiffeners increased the ultimate strength and improved the stability of the columns. Subsequently, the behaviour of the stiffened CFST columns was investigated by performing a three-dimensional FEA. The accuracy of the FEA model was verified based on the test results. The working mechanisms of the stiffened CFST members were analysed in detail in terms of the failure modes, load versus deformation responses, deformation of the steel tubes, interaction between the steel tube and core concrete, as well as axial stress distribution of the core concrete. A parametric study was conducted to further evaluate the stiffening schemes that affected the ultimate strength and ductility of the CFST members. Finally, design recommendations on the type of eccentrically-loaded stiffened CFST columns were provided.