Bearing capacity of high-strength concrete-filled SHS and RHS Steel tubular members subjected to axial compressive load and biaxial bending moment

This paper firstly analyzed four possible loading-paths for concrete-filled steel tube (CFST) columns subjected to axial compressive load and biaxial bending moment. Then two typical loading-paths existing in the engineering practice were used to investigate the bearing capacity of CFST columns with special consideration for loading and unloading effects. On basis of the axial compression experiments of stocky columns, a nonlinear numerical program was developed to analyze effects of the loading-paths and loading-angles on the cross-section strength and the in-plan stability of the columns. Moreover, this paper illustrates the three-dimensional interrelated surfaces for the strength and the in-plan stable capacity. Finally, analytical results show that as far as square hollow section (SHS) in concerned, the two typical loading-paths have about 4% difference on the strength and the in-plan stable capacity, in addition, the loading-angles have no effect on the strength and have little effect on the in-plan stable capacity; as far as rectangular hollow section (RHS) is concerned, the two typical loading-paths lead to only about 5% difference on the strength and the in-plan stable capacity, however, it is worthy of attention that the loading-angles produce greater effects on them.