Study On Mechanical Behavior Of Thin-walled Cold-formed Concrete-filled Steel Tubular Stub Columns

To provide reference for the use of thin-walled cold-formed concrete-filled steel tubular(CFCFST)columns with width-thickness ratios exceeding the limit of the code in engineering construction,based on the improved constitutive model of cold-formed steel,the finite element analysis was adopted to discuss the mechanical behavior of thin-walled CFCFST columns with different parameters.The main work is as follows:(1)Based on the experimental data collected by domestic and foreign literatures,the material analysis of plate and corner part of cold-formed steel is analyzed.Summarize the existing constitutive relation models of cold-formed steel.According to the experimental data,the limit strain of the corner of cold-formed steel and the parameters of constitutive drop section are calibrated.The complete constitutive model of the cold-formed steel and the calculation method of the key points of different strength grades are obtained.Then the improved constitutive mode has been compared with the experimental data.(2)Using finite element software,establish the thin-walled square and rectangular CFCFST columns,which is in good agreement with the experimental results.By establishing 192 models,compare the stress development,failure modes and ultimate bearing capacities of the hollow and concrete-filled steel tubes during loading.The effects of width-thickness ratio,section size,area ratio of corner part to full section of cold-formed steel tube,steel grades,and material matching on the ultimate capacity of thin-walled CFCFST columns,the composite behavior between steel tube and concrete were further investigated.The results can provide a reference for the design and application of thin-walled CFCFST columns with large width-thickness ratios in actual engineering.(3)The classifications of the bearing capacity were summarized and the applicability of the formula to the concrete-filled steel tube in domestic and foreign norms was evaluated.Based on the finite element model,the calculation formula for determining whether the steel tube has local buckling and the design method of the bearing capacity of thin-wall square and rectangular CFCFST columns is proposed.