Study On Bearing Capacity Of Concrete-filled Circular Stainless Steel Stub Columns Under Axial Compression

Due to good corrosion resistance and high strength,the concrete-filled stainless steel tube（CFSST）structure has a wide application prospect in coastal construction,space structure and underground engineering.In order to study the bearing capacity of circular CFSST columns under axial compression,the axial compression tests of austenitic seamless CFSST columns with different wall thicknesses were carried out.The failure modes,load and axial displacement curves,load circumferential strain and axial strain curves,and the relationship between bearing capacity and the wall thickness of stainless steel tube were obtained.On the basis of the test,the reasonable finite element model was established by using the finite element software ABAQUS,and the parametric analysis including different wall thickness,concrete strength and restraint effect coefficient was carried out.And the axial force distribution between the stainless steel tube and core concrete was studied.Furthermore,through the linear fitting,the formula for predicting the axial compression bearing capacity of the circular CFSST short column was obtained.The prediction results were compared with the existing specifications in the world.Finally,according to the fitting formula,the bearing capacity model of circular CFSST short column was derived,and compared with Mander’s model,Li’s model,Xiao’s model and Teng’s model.The results show that the typical failure mode of circular CFSST stub columns under axial compression is local buckling failure.Additionally,the restraint effect,ductility and bearing capacity of the specimens increase with the increase of wall thickness.The results show that the finite element model established in this paper is in good agreement with the experimental results.With the same wall thickness,the increase range of ultimate bearing capacity of circular CFSST short column is from 30 to 40 MPa,from 50 to 60 MPa,and from 40 to 50 MPa.Besides,with the same concrete strength,the increasing range of ultimate bearing capacity decreases with the increase of wall thickness.Different from the concrete-filled steel tube（CFST）,when ξ_ss<1.2,the load axial displacement curve of CFSST column reaches the peak point,then decreases briefly,finally continues to rise.The load distribution between the stainless steel tube and core concrete can be divided into three categories.When ξ_ss<ξ₁,the axial load borne by concrete is greater than that of stainless steel tube.When ξ_ss>ξ₂,the result is just different from that of ξ_ss<ξ₁.When ξ₁<ξ_s<ξ₂,firstly,the axial force borne by concrete is more than that of the stainless steel tube,and then,the result is on the contrary.The prediction results of the ultimate bearing capacity of circular CFSST columns through the method of CFST columns is smaller compared with the tested results.And the calculated value by the fitting formula in this paper is closer to the test result.At the same time,the results of the bearing capacity model proposed in this paper,Xiao’s model,and Teng’s model are close to the test results.However,the standard deviation of the calculation results by this model proposed in this paper is the smallest.And the bearing capacity calculated by this model is slightly larger than those of Xiao’s model and Teng’s model.