Analysis Of Axial Compression Bearing Capacity Of Concrete Filled T-shaped Steel Tube Column

Concrete-filled specially shaped steel tube columns are more and more popular in modern building structures,which can improve the external appearance of the building,the utilization of internal space,and superior bearing performance and seismic performance.The main cross-section types are T-shaped,L-shaped and cross-shaped.At present,the researches of scholars at home and abroad mainly focus on the bearing capacity of axial compression short columns,the bearing capacity of biased short columns and seismic performance.However,there are few studies on the stability of axial compression slender columns,and no normative guidance documents are formed.So,Concrete-filled specially shaped steel tubular concrete members cannot be conveniently and quickly applied in engineering practice.In view of this situation,based on the axial compression test of concrete filled T-shaped steel tube column(CFTST)by Dr.Lei Min,this paper makes a comprehensive and in-depth study on the axial compression performance of CFTST columns from numerical simulation and theoretical analysis.The work carried out is as follows:1)Based on the stress-strain constitutive model of the core concrete of rectangular concrete-filled steel tubular columns established by senior scholars,considering the influence of aspect ratio,the stress-strain constitutive model of the core concrete of CFTST columns is obtained through correction.The ABAQUS finite element model of the concrete-filled steel tubular short column is combined with the T-shaped concrete-filled steel tubular axial compression short-column test results of Dr.Lei Min of Tongji University to verify the rationality of the finite element model.2)Using ABAQUS finite element software to analyze the whole process of load-displacement of CFTST stubs,then carry out a large number of parameter analysis,and use the mathematical analysis software 1stopt to regress the core concrete strength improvement coefficient,and finally,The formula for calculating the strength bearing capacity of CFTST stubs is proposed.Comparing the calculation results of the theoretical formula and the calculation results of relevant national norms with the experimental results of Dr.Lei Min,it is proved that the theoretical formula has higher calculation accuracy.3)Study and summarize the basic principles of the fiber model method,and prepare a fiber model program suitable for studying the axial compressive bearing capacity of CFTST slender columns with axial compression,combined with the test results of CFTST slender column of Dr.Lei Min of Tongji University.The comparison verification proves the rationality of the fiber model program.4)According to the stress conditions of the axially-force slender column members in the actual engineering and related specifications,the fiber model program is used to parameterize the CFTST slender columns according to the initial deflection and initial eccentricity.Based on the analysis,considering the influence of aspect ratio,the stability bearing capacity along the x direction,+y direction and-y direction is studied.Finally,a simplified calculation formula for the stable bearing capacity of CFTST slender columns is proposed.Some components are randomly selected for calculation,and the simplified formula calculation results are compared with the fiber model calculation results.The rationality of the simplified formula is proved,which can provide reference for engineering design and related specifications.