Analysis Of Interfacial Shear Slip Behavior Of Steel Concrete Composite Beams Under High Temperatures

The steel beam and concrete slab form a load-bearing whole through shear connectors,which is called a steel concrete composite beam.The steel concrete composite beam has the advantages of steel and concrete structures,while avoiding the shortcomings of steel and concrete structures,and is widely promoted and applied in the construction field.However,due to the poor fire resistance of steel,the mechanical properties of the material will be degraded under high temperature of fire,resulting in the increase of slip between the interface of the composite beam,reducing the integrity of the structure,and ultimately leading to the destruction of the structure.Therefore,it is of great significance to study the interface slip effect of steel concrete composite beam structure under high temperature of fire.At present,many scholars at home and abroad have systematically studied the performance of composite beams at room temperature,and have given mature theories and design methods.However,the research on the fire resistance of composite beam structures under high temperature is not comprehensive enough.Most literatures rarely consider the change of shear slip between composite beams.However,the existing structural fire resistance test results show that the high temperature of fire has a non-negligible influence on the interfacial shear slip performance of steel concrete composite beams.Therefore,based on the previous research results,this paper uses theoretical research and numerical simulation to analyze and discuss the change of interfacial shear slip performance of steel concrete composite beams under high temperature.The main research contents are as follows:(1)The mechanical properties and thermal parameters of structural steel and concrete under high temperature are summarized.The appropriate calculation parameters are selected to provide the basis for subsequent theoretical analysis and numerical simulation.(2)The theoretical calculation model of interface shear slip of steel concrete composite beam structure under high temperature is established and the basic assumptions are put forward.Based on the global-local slip theory and nonlinear elastic theory,the equations of interface shear slip and deflection deformation are established,and the calculation expressions of interface shear slip and deflection deformation of composite beam under high temperature are given.(3)Based on the ISO834 international standard fire heating curve,the slip deformation of steel concrete composite beams was simulated and analyzed by ABAQUS finite element software.The temperature field changes inside the composite beams at different fire moments were obtained.The simulation of the temperature field was compared with the experimental values of the relevant literature,and the feasibility of using ABAQUS finite element software to study the fire temperature field of the composite beam structure was verified.(4)The temperature field analysis results are introduced into the structural analysis,and the thermal-mechanical interaction analysis of the steel concrete composite beam structure is carried out.The spring element is used instead of the solid stud,and the nonlinear stiffness of the spring is defined according to the force-displacement-temperature curve of the existing stud test.On this basis,the interface shear slip performance and deflection deformation of the steel concrete composite beam structure under high temperature of fire are calculated and analyzed.The theoretical calculation,simulation analysis and the experimental results of the relevant literature are compared to verify the rationality of the theoretical analysis and numerical model.(5)The finite element simulation analysis of the three parameters of load type,load ratio and shear connection degree of steel concrete composite beams under high temperature of fire is carried out.The interface shear slip and mid-span deflection comparison diagram along the beam length direction at different temperatures are obtained.The influence of three parameters of load type,load ratio and shear connection degree on the interface shear slip performance of composite beams under high temperature is discussed.