Experimental And Theoretical Study On The Bond Properties At The Interface Of Concrete-Filled Square Steel Tubes

The bond strength and the bond-slip constitutive equations at the interface between the steel tube and the concrete of concrete-filled square steel tubes (CFSST) is one which is further concerned by more and more construction engineers and managers. The study on the bond-slip behaviors at the interface of CFSST is significant on the theory and utility value.In this paper, axial push-out test of CFSST is completed. Based on the results of experiment, the bond strength of the interface between the steel tube and the concrete in CFSST is studied. The influencing factors of the bond strength are discussed. The factors which affect the bond strength of CFSST are analyzed by Grey connection. Based on the date of this test and the former tests, a calculation formula of the bond strength is established. The checking computations of the bond strength of the joint of CFSST is given, this method can be used in the practice structure.The numerical simulation of the push-out test specimens were conducted with the ANSYS program, the simulation results were good agreement with the experimental results, therefore, the methods of numerical simulation of CFSST push-out test specimens in ANSYS program presented in this paper could be introduced into the simulation of the CFSST members and structures.The CFSST under axial load was numerically simulated with the ANSYS program, the two cases considering and not considering the bond-slip performance between steel tube and concrete were both conducted and compared with the experimental results. The influence of the bond-slip and different types of loading conditions on mechanical behaviors of CFSST under axial load is analyzed.