Study On Axial Pressure Behavior Of Concrete Filled Steel Tubular Short Columns With Variable Sections

Variable-section concrete filled steel tubular is a kind of composite structure whose section size changes along the axis direction.The existence of variable angle makes the stress of outer steel tubular and core concrete more complex and the overall performance of compressive columns changed.In this paper,experimental research and finite element analysis are used to analyze the axial compressive performance of variable-section concrete filled steel tubular short columns,and on this basis,the combination is made.A practical method for calculating the bearing capacity of concrete-filled steel tubular stub columns with variable cross-section is proposed based on the research results on the axial compressive behavior of concrete-filled steel tubular stub columns with equal cross-section.This paper mainly studies the following aspects:(1)Eight CFST stub columns with variable cross-section were tested under axial compression.The effects of variable angle and steel content on the failure mode,ductility and ultimate bearing capacity of the stub columns were analyzed,and the whole process of compression was analyzed.(2)Based on the analysis of finite element software ABAQUS,the simulation problems of steel tube constitutive relation,concrete constitutive relation,steel tube element,concrete element,steel-concrete interaction and model mesh generation in concrete filled steel tube with variable cross-section are solved effectively,and the end loading method of adding rigid plate,coupling end to one point and direct loading end surface is limited.Meta-models and their application scope are presented.The experimental results are used to verify the finite element model established in this paper.(3)Eighty variable-section specimens with different parameters were established by finite element software ABAQUS,and the parameters affecting the mechanical properties of variablesection concrete filled steel tubes,such as steel ratio,angle,steel strength and concrete strength,were compared and analyzed.The influence laws of each parameter on the overall performance of axially compressed columns,external steel tube force,core concrete force and steel-concrete interaction were obtained.(4)By introducing the formula for calculating the bearing capacity of concrete-filled steel tubular short columns with constant cross-section,comparing the columns with constant crosssection and variable cross-section under axial compression,analyzing the reasons for the change of the bearing capacity of variable cross-section concrete-filled steel tubular short columns,putting forward a practical method for calculating the bearing capacity of variable cross-section concrete-filled steel tubular short columns,and calculating the previous tests with the practical calculation method,Reliability.