Research On Axial Compression And Seismic Performance Of Of Square Steel Tube-concrete-circular Steel Tube Composite Column

This paper proposes a square steel tube-concrete-circular steel tube（HSCS）composite column.It’s insist of the inner and outer steel tubes are placed concentrically,and the ring concrete is filled between them.Steel tube can effectively improve the axial compression performance of this composite columns,and it can not only provide the necessary confinement effect for concrete,but also provide part of the axial compression gain.The ring concrete is constrained by the outer steel tube and laterally supported by the inner steel tube,which causes it to be in a three-dimensional stress state,which effectively improves the ability of the composite column to resist deformation.Due to the supporting effect of the ring concrete,it can effectively delay or avoid local buckling or global buckling failure for the steel tube in the process of axial compression.In order to study the axial compression performance of the square steel tube-concrete-circular steel tube（HSCS）composite short column,27 HSCS specimens are designed by considering the main parameters of compressive strength(f_ck)of the ring concrete,the tensile strength(f_yo),thickness（t_o）and width（B）of the outer steel tube,the tensile strength(f_yi),thickness（t_i）and diameter（D）of the inner steel tube,the slenderness ratio（λ）and section hollow rate（T）.Based on a reasonable material constitutive model,mash rationality analysis and verification analysis of existing test specimens,the prediction accuracy of the model is determined,furthermore the influence of each parameter on the axial compression performance of the full-size HSCS short column is obtained.The results show that with the increasing of B,t_o,f_yi,f_yoand f_ck,the axial compression bearing capacity of this specimens is significantly improved,but with the increasing of T,it gradually decreases.The best value of T is recommended to be 0.1～0.3.Finally,the calculation expression of the axial compression bearing capacity of the HSCS short column is derived,which has high prediction accuracy and can meet the needs of engineering practice.With the help of a reasonable finite element modeling method,the axial compressive strength(f_ck)of the ring concrete,the tensile strength(f_yo),thickness（t_o）and width（B）of the outer square steel tube,and the tensile strength Strength(f_yi),thickness（t_i）and diameter（D）of the inner steel tube,the axial compression ratio（n）and hollow rate（T）of the HSCS specimen as the control parameters.Based on ABAQUS software,the seismic performance simulation of 19 HSCS composite columns is carried out.The influence of different parameters on the hysteretic performance is analysised,and the skeleton curves,resistance attenuation,energy dissipation capacity and stiffness degradation of HSCS composite columns are also obtained.In view of the relatively excellent seismic performance and load-holding capacity of this new type of HSCS composite column,it is recommended that the practical application of this type of composite column be widely promoted.