Push-out Test Research On The Interfacial Anti-shear Performance Of Concrete-filled Square Steel Tube Stiffened With PBL

Concrete-filled Square Steel Tube stiffened with PBL is a type of composite structure,in which PBL are weld together by tube wall.PBL connector can improve the interfacial anti-shear bearing capacity of CFST and prevent disengaging of CFST interface.It also can stiffened the tube wall.At present,there are some researchs of this specimen's axial compressive performance and node fatigue resistance performance,while there aren't researchs for interfacial anti-shear performance.Therefore,to investigate the interfacial anti-shear performance of this specimen,the main works in this paper are presented as following:(1)A total of 17 test specimens were used in the Push-out test,by which the effects of coarse aggregate size,hole spacing of PBL and radius of PBL.The interfacial failure mechanism and interfacial anti-shear performance were also studied.The distribution regularities of coarse aggregate were also studied.The result show that:the interfacial anti-shear performance of Concrete-filled Square Steel Tube stiffened with PBL is good;Appropriately increase the coarse aggregate size,the radius of PBLand decrease the hole spacing of PBL can effectively improve the interfacial anti-shear bearing capacity.The Ag/Ac is fixed,when use the same coarse aggregate size and the radius of PBL is different.(2)Using the common FEM software ABAQUS,a series of numerical models of specimens were built by adopting the appropriate material constitutive relation and their valedities were verified by the test results.And on this base,the effecti of the concrete strength,steel yield strength of PBL,hole spacing of PBL,width thickness ratio of PBL on C specimens were investigated.The numerical results show that increase the concrete strength and hole spacing of PBL are the main influence parameters of interfacial anti-shear performance.To avoid stress concentration of concrete in PBL,the hole spacing of PBL to be 2d is better.The steel yield strength of PBL and width thickness ratio of PBL did not affect interfacial anti-shear performance.(3)Through the analysis of experiment and finite element results,and combining with domestic and foreign test data,it can be found that interfacial anti-shear capacity of PBL increased by linear growth trends with the bigger hole diameter.It can be found that interfacial anti-shear capacity of PBL increased by parabolic growth trends with the bigger hole radiu.It can be found that interfacial anti-shear capacity of PBL increased by linear growth trends with the bigger Ag/Ac.A new equation for PBL calculation has been suggested.According to the principle of superposition,on the basis of the square steel tube and core concrete interface shear bearing capacity calculation formula and PBL connector formula to calculate the shearing resistance,this has made a proposed formula to interfacial anti-shear bearing capacity of Concrete-filled Square Steel Tube stiffened with PBL.