Study On The Axial Compression Performance Of New Type Steel-concrete Composite Column

Under the background of increasing demand for super high-rise structure and largespan heavy load structure,steel-concrete composite columns are applied more and more in engineering.Based on the concrete filled steel tubular composite column and steel reinforced concrete composite column,this paper proposes a new type of composite column: new type of steel reinforced concrete composite column,which strengthens the restraint effect of concrete around the steel tube,optimizes the coordinated deformation of concrete inside and outside the steel tube,gives better play to the compressive performance of concrete,and improves the bearing capacity and deformation capacity of composite column.The experimental study,numerical simulation and theoretical analysis of the axial compression performance of this type of composite columns are carried out.The main contents and conclusions are as follows:(1)The axial compression test of new type steel-concrete composite columns was carried out.The influences of flange width,flange thickness,web height,different section forms and volume stirrup ratio on the axial compression behavior of composite columns are analyzed;The results show that the ultimate failure state of different section types of composite columns is similar,and the decrease of bearing capacity is caused by the spalling of concrete cover around stirrups;In addition,after the peak load,the advantage of CFST in the new type steel-concrete composite column is brought into full play,and the ductility of the composite column is improved.(2)The numerical simulation analysis of the new steel-concrete composite column is carried out.ABAQUS software is used to simulate the existing tests.On the basis of verifying the correctness of the model,the influence of more parameters including material properties(concrete strength,steel strength)and geometric parameters(section steel size,steel tube diameter thickness ratio,web opening size and opening form)on the axial compression performance of composite columns is further analyzed.The results show that the strength of concrete around the steel tube has great influence on the strength coefficient,ductility coefficient and peak load of composite columns.The increase of diameter thickness ratio of steel tube can improve the ductility of composite columns and improve the residual bearing capacity of composite columns;The results show that the web openings have little effect on the axial compression performance of composite columns,and the peak load of composite columns is circular,rhombic and rectangular from large to small according to the web openings.(3)A new method for calculating the axial bearing capacity of steel-concrete composite columns is established.Considering the restraint of stirrups,steel flanges and steel tubes on concrete,a new calculation method of axial bearing capacity of steelconcrete composite columns is established based on the twin shear unified strength theory and stress mechanism;The calculation results are compared with the experimental data and simulation results,and the results show that the axial compression bearing capacity calculation method can better predict the bearing capacity of the new steel-concrete composite column.