RESEARCH ON MECHANICAL BEHAVIOR FOR HIGH STRENGTH CONCRETE-FILLED SQUARE STEEL TUBULAR COLUMNS

Through the low cyclic load test of eight high strength concrete-filled square steel tubular columns, considering the effect of the axial compression ratio, steel ratio and slenderness ratio, the hysteretic curve, ductility, degradation of stiffness, energy dissipation capacity, failure mechanism and characteristics of the specimens were researched. The influence law of the axial compression ratio, steel ratio and slenderness ratio on the mechanical and seismic behavior of these columns were analyzed. The results indicate that the high concrete-filled square steel tubular columns have plump hysteretic loops, stronger energy dissipation capacity, and good ductility after the specimens reach ultimate loads, that the displacement ductility coefficient is between 3.05 and 4.07, and that the columns can meet the requirement of ductile specimens. The axial compression ratio has larger influence on the load-carrying capacity and the seismic behavior, with the increment of the axial compression ratio, the load-carrying capacity decreases, the displacement ductility and energy dissipation capacity reduces, and the stiffness degradation is faster; with the increment of steel ratio, the load-carrying capacity and elastic stage stiffness increase, and the displacement ductility and energy dissipation capacity increase; with the increment of the slenderness ratio, the load-carrying capacity and elastic stage stiffness reduce obviously.