Experimental Research on The Confinement Effect for the Composite Concrete-Filled Square Steel Tubular Short Columns

Through the axial compression tests of two ordinary concrete-filled square steel tubular(CFSST) short columns and six composite CFSST short columns, the influence laws of section types, confinement coefficient, steel ratio and concrete strength on the mechanical behavior of the CFSST short columns were studied. The results show that in CFSST columns, the change of steel tube's section form can improve effectively the cooperative work ability between the steel tube and core concrete, enhance the restraint effect of the steel tube on the core concrete, delay or inhibit the development of inclined cracks in the core concrete, increase the ductility and improve significantly the ultimate bearing capacity when the steel ratio or confinement coefficient is close to each other. With the increment of the confinement coefficient and steel ratio, the bearing capacity and ductility improve.