Axial Compressive Behavior Of CFDST Stub Columns With Large Hollow Ratio

Concrete-filled double-skin steel tube(CFDST)is a new kind of composite member,and it is formed by replacing core part concrete of traditional concrete-filled steel tube(CFST).CFDST not only meets the requirements of the structure for bearing capacity and stiffness,but also has lighter self-weight and better seismic performance.At present,CFDST has been used in a few transmission towers and bridges,and the hollow ratio in the study and engineering application is generally less than 0.75.With the continuous increase of the structural sizes and the requirements for space utilization and cost performance,CFDST with large hollow ratio(greater than or equal to 0.8),which has broad application prospects,gradually shows engineering needs.As a result,studying the behavior and design method of CFDST members with large hollow ratio can provide a basis for its engineering applications.In this paper,the research method of the combination of experiment and finite element simulation is used to conduct an in-depth study on the axial compressive behavior of CFDST stub columns with large hollow ratio.The main work is as follows:(1)Nine CFDST [circular hollow section(CHS)inner and CHS outer] stub column specimens with large hollow ratio are designed and tested.The influence of hollow ratio,outer steel tube diameter-thickness ratio and concrete strength on the failure pattern,load versus deformation curves,bearing capacity and composite elastic modulus of the tested specimens is investigated.(2)On the basis of determining the constitutive model of steel and concrete,a threedimensional nonlinear finite element model of the axially loaded CFDST stub columns with large hollow ratio is constructed by a general software ABAQUS.The simulation results of the finite element model generally accord well with the experimental results in this paper,which proves the rationality of the finite element model.(3)Using the nonlinear finite element model verified by the test results,the influence of the hollow ratio and the nominal steel ratio concrete strength on the mechanism of CFDST stub columns with larger hollow ratio is systematically analyzed.(4)Based on the stress distribution characteristics of the sandwichd concrete and inner steel tube simulated by the finite element model,the calculation method for the bearing capacity of the CFDST stub columns with large hollow ratio is determined.