Experimental Study On Bond-slip Behavior Of Thin Walled Concrete-filled Stainless Steel Tube

The bond strength and bond-slip constitutive relation between steel tube and concrete are the main topics of concrete filled steel tube(CFST).The structure of concrete-filled stainless steel tube(CFSST)not only has good mechanical properties of ordinary CFST,but also has excellent durability of stainless steel.Therefore,the bond slip of thin-walled CFSST is studied in this paper.Repeated push-out tests of 32 circular and 32 square CFSST specimens are completed in this paper,which studies the effects of height-diameter(width)ratio,diameter(width)-thickness ratio,strength of concrete on shear bond strength.In addition,the strain distribution on outer surface of 4 circular and 4 square CFSST specimens are tested.Based on the results of experiment,the failure characteristics of the interface,the composition of the bonding force and the main factors affecting the bond strength are discussed.Besides,the variation characteristics of load slip curve and the variation of the strain distribution on outer surface in the process of bond failure are summarized.Then the experimental results are compared with the calculated values of bond strength from existing calculation formula of CFST.Result shows that the calculation formula of CFST does not apply to thin-walled CFSST,so it's necessary to put forward a more reasonable formula of bond strength.On the basis of the experiment,the finite element simulation of thin-walled CFSST is carried out,the load slip curve and the ultimate bond strength are in good agreement with the test results.In addition,the parameters of thin-walled CFSST are analyzed with the verified finite element model.The main research parameters are height-diameter ratio,diameter-thickness ratio and strength of concrete for circular thin-walled CFSST.The main research parameters are height-width ratio and width-thickness ratio for square thin-walled CFSST.Finally,the suggested formula of bond strength of thin-walled CFSST is put forward based on the finite element analysis.The calculated value of the proposed formula is in good agreement with the finite element results of the parametric analysis,which can provide some reference for practical engineering.