Study On The Mechanical Behavior Of Concrete Filled Stiffened Square Steel Tubular Middle Long Column Under Axial Compression

Concrete-filled steel tubular column(CFST)is a composite member formed by pouring concrete into the steel tubular column.However,when the section of the members is square or rectangular,the mechanical properties of CFST members are affected by the local buckling of the pipe wall with the increase of the width-thickness ratio of the members,which seriously restricts their application in engineering.Therefore,in addition to determining the reasonable design method,the structural measures to improve its mechanical properties should also be studied.In view of this,this paper studies the mechanical properties of square concrete-filled steel tubular columns with stiffeners from both experimental and theoretical aspects.Axial compression tests were carried out with length-fineness ratio,width-thickness ratio and height-thickness ratio of stiffeners as experimental parameters.The influence of the aspect ratio,the width and thickness ratio and the height and thickness ratio of stiffeners on the bearing capacity of the medium and long columns with ribbed square concrete-filled steel tubes is analyzed by using the orthogonal test method.The results show that the stiffening rib can significantly increase the bearing capacity of CFST,and the core concrete can be restrained more effectively.The mechanical properties of CFST medium and long columns with stiffeners were obviously improved,the local bulging of steel tube wall was delayed,the material strength was fully utilized,and the bearing capacity of specimens was improved.The stability coefficient of medium and long columns under axial compression affected by slenderness ratio is improved,which improves the bearing capacity of medium and long columns.The analysis of orthogonal design shows that the bearing capacity of medium and long columns is most affected by the ratio of width to thickness.The bearing capacity of stiffener is also affected by the ratio of height to thickness and ratio of length to fineness.ABAQUS software was used to simulate the whole process of load-deformation of the test member,and the influence law of stiffener on the stress distribution of steel tube and concrete,the bearing capacity of the member and the failure form of the specimen wasanalyzed.The simulation results were consistent with the test results,which verified the reliability of the finite element model established in this paper.Based on the experimental and simulation data,this paper refer to the predecessors’ research results,comprehensive consideration of stiffener and direct impact on the bearing capacity of impact on the stability factor of the change with slenderness ratio,proposed the ribbed square concrete filled steel tube long column under axial compression bearing capacity calculation formula,and the calculated results compared with the experimental results,both are in good agreement,for the class members to provide the reference in the subsequent research and engineering practice.