Numerical Simulation Of Steel Tube Column Concrete Under High Temperature Stress

Concrete steel-filled steel tubular column(CFST)is a kind of composite component composed of external steel pipe and core concrete,which has been widely used in engineering projects.On the basis of previous research,this paper explores the influence of different factors on the residual bearing capacity of long and short steel tubular concrete columns under high temperature(fire)by numerical simulation.The effects of fire time,cross section size,material strength,fire layer thickness and ratio of length to fineness on the reduced bearing capacity of long and short steel tube concrete columns after high temperature(fire)were studied.The main tasks are as follows:(1)The process of heat transfer of CFST under high temperature(fire)is systematically summarized.Based on this,the temperature field model and mechanical analysis model of CFST are established using ABAQUS software,and the relevant test data and simulation results are compared.The accuracy of the finite element model is verified.(2)The effect of different steel tube section sizes on steel tubular column concrete is studied by using temperature field model.The results show that the thickness of steel pipe has a great influence on the temperature gradient of concrete.The larger the thickness of the steel pipe,the more gentle the temperature gradient will be.The protection layer of fireproof coating has a significant effect on the temperature field of the sample,but it has little effect on the temperature change of the internal core concrete.(3)The influence of different factors on the mechanical properties of short columns of steel tubular concrete is studied by means of mechanical analysis model.The results showed that the mechanical properties of the short column were significantly affected by fire mode,cross section size,fire layer thickness and fire time.The maximum stress of the two sides of the fire appears in the center of the backfire surface,and the maximum stress of the three sides of the fire appears between the backfire surface and the core concrete;The larger the cross section size,the larger the fire layer thickness,the shorter the fire time,the greater the residual bearing capacity of the short column member after the high temperature(fire),and the less damage the member has.(4)The influence of different factors on the mechanical properties of long column steel tubular concrete is studied by means of mechanical analysis model.The resultsshow that the type of support,cross section size,fire layer thickness,time of fire and ratio of length to fineness have a significant effect on the mechanical properties of concrete tubular columns.After high temperature(under fire),the member with hinged ends or one end fixed end is deformed,the mechanical performance is good,and the long column member with fixed ends is deformed.The larger the size of the surface,the greater the thickness of the fire layer,the shorter the length of the fire,the smaller the ratio of the length to the length of the long column member after the high temperature(fire)has a large impact on the residual bearing capacity,and the damage of the member is small.