Research On Construction Simulation And Ultimate Bearing Capacity Of Post-cast Horizontal Concrete-filled Square Steel Tubular Components

Concrete Filled Steel Tube(CFST)refers to the steel tubes with concrete infilled.Owing to the high bearing capacity,seismic performance,fire resistance,economic performance and other advantages,it has been widely used in various structural systems like large-span stadiums,high-rise building and bridge.Large-span spatial structures often encounter horizontally or aslant placed CFST components.With the "Branch Pipe First,Pouring Later" principle of the construction process,wet concrete will arouse relatively high initial imperfection and initial stress on steel tubes after the concrete acquires rigidity.Taking this practical situation into account,this article took the horizontal Post-cast CFST applied in the lower compressing ring of the wheel-spoke shaped pretension structure of the Foshan Century Lotus Stadium as research object.The ABAQUS 6.13-1 software package was used to conduct finite element analysis on its axial compression resistance performance.Contents are as follows:1)Based on the practical construction sequences and the assumptions of relevant publications,the author put forward the construction simulation method of horizontal Post-cast square steel tube and conducted construction simulation on it with birth-death element technique and trace element technique,to obtain the action position of horizontal Post-cast CFST components after having rigidity for wet concrete pouring;2)The author conducted the secondary development on ABAQUS with Python programming language script,in accordance with parametric modeling analysis platform framework,to achieve batch processing of parametric modeling and result data of horizontal post-cast square CFST/ordinary square CFST components;3)Finite element models,which are established on the parametric modeling analysis platform framework,are validated by comparing the experimental data of the current published articles;in view of the influence of initial stress and initial imperfection on the components' bearing capacity,construction influence coefficient ? is proposed,which is then researched by taking these parameters such as thick to width ratio t/B,strength of steel fy,strength of concrete fcu and length to width ratio L/B into consideration.The numerical analysis results shows that the coefficient ? was mainly controlled by length to width ratio L/B and thick to width ratio t/B,while the influence of steel strength and concrete strength was negligible.4)On the basis of the numerical results,fitted equation of ? is proposed by taking length to width ratio L/B and thick to width ratio t/B as independent variables,with the use of MATLAB software.According to the calculation principle of the original long CFST in code of ? Technical Specification for Concrete-filled Steel Tube Structure ?(DBJ13-51-2003),the corresponding design equation of the horizontal post-cast CFST long components is put forward by the author.The research indicates that the numerical analysis result agreed well with the fitted equation.Therefore,the formula can be applied to calculate the ultimate bearing capacity of long horizontal post-cast square CFST components,in addition to providing reference for the engineers.