Study On The Mechanical Properties Of T-Shaped Concrete Filled Steel Tubular Columns After High Temperature

The section forms of special-shaped concrete filled steel tubular columns are varied,such as T-shaped,L-shaped,V-shaped,Z-shaped,cross-shaped and so on.Different cross-section forms can be chosen according to the needs of the building,the limb width of which can be made as thick as the filling wall of the structure.It effectively avoids the appearance of pien of the structure in the corner or the edge column position,making the structure in the overall plane is very regular,and the building shape is more beautiful.Special-shaped concrete-filled steel tubular columns can meet the requirements of different building functions and structural layout systems.Now they are more and more widely used.With the rapid development of the construction industry,complex buildings and complex conditions make building structures have more potential fire hazards,especially in high-rise and super-high-rise buildings with higher comprehensive.Special-shaped concrete-filled steel tubular columns are widely used in modern high-rise and super-high-rise buildings.In order to fully understand the residual mechanical properties of special-shaped concrete-filled steel tubular columns after fire(high temperature),and to provide design suggestions for damage assessment and reinforcement and repair of such structures after fire(high temperature),in this paper,the mechanical properties of T-section concrete-filled steel tubular columns after high temperature under different influencing factors are discussed by means of experiment and finite element ABAQUS.The calculation method of ultimate bearing capacity of T-section concrete-filled steel tubular columns after high temperature is fitted with mathematical analysis software MATLAB,which takes into account the variables of steel ratio 、high temperature and the duration of high temperature.This will promote the further study of concrete-filled steel tubular structures with special-shaped sections.Supported by the National Natural Science Foundation of China(No.51778065),the finite element simulation is carried out on the basis of the experiment,which is mainly based on the experimental research.The main work is as follows:(1)In the experiment,thirty specimens were designed and manufactured with the main change parameters,e.g.the thickness of steel tube(steel ratio),high temperature and the duration of high temperature.Twenty-seven of which were subjected to axial compression test after heating operation.The failure mode,load-displacement relationship,load-strain relationship and ultimate bearing capacity of the specimen were studied.The results show that after high temperature,the two components of T-shaped concrete filled steel tubular short columns are deformed in harmony,and the overall force is uniform.The failure modes of T-shaped concrete filled steel tubular short columns include local cracking,buckling failure and shear failure.The influence of high temperature on the residual bearing capacity of specimens is more significant.The higher the temperature is,the lower the ultimate bearing capacity is.(2)Based on the experimental results,referring to the relevant theoretical results of concrete filled steel tubular structures at home and abroad,and combining with the mathematical analysis software MATLAB,the formulas for calculating the ultimate bearing capacity of T-section concrete filled steel tubular columns after high temperature considering the variables of steel ratio,high temperature and the duration of high temperature are fitted.(3)By referring to the relevant literature,analyzing the experimental results and reviewing the existing theory of temperature field,considering the changes of the properties of steel tube and concrete,the contact between concrete and steel tube surface after high temperature,selecting a more appropriate constitutive relationship,establishing the finite element model of T-shaped concrete filled steel tubular short column under axial load through the finite element software Abaqus,and simulating the T-shaped steel tube after high temperature.The failure modes of concrete short columns under axial compression load are compared with the experimental failure modes.The load-displacement relationship curve is drawn and the load-displacement relationship curve is compared by continuously adjusting the relevant parameters to match the experimental results.The results show that the finite element model is in good agreement with the experiment and can better reflect the stress state of the experimental components.