MECHANICAL BEHAVIOR OF SQUARE STEEL TUBE SHORT COLUMNS FILLED WITH RECYCLED AGGREGATE CONCRETE UNDER AXIAL COMPRESSION AFTER HIGH TEMPERATURE

Twenty-four specimens were designed to study the mechanical behavior of square steel tube short columns filled with recycled aggregate concrete under axial compression after high temperature． Two parameters，i． e replacement ratio and temperature were taken into consideration． The damage process and failure mode of specimens were observed，and stress-strain curve and ultimate bearing capacity as well as other important data were obtained by test． The effects of replacement ratio and temperature of that new kind of composite structures were investigated． The method to calculate ultimate bearing capacity of square steel tube short columns filled with recycled aggregate concrete under axial compression after high temperature was analyzed． The results indicated that the ultimate bearing capacity and elastic stiffness of the specimens after high ten perature presented a decrease trend with an increase temperature． With the increasing of temperature，ductility and energy dissipation first decreased and then increased． An increase recycled aggregate replacement ratio decreased the bearing capacity but increased ductility and energy dissipation． While increasing recycled aggregate replacement ratio，the elastic stiffness first increased and then decreased．