Analysis Of Mechanical Characteristics Of Steel Frame Structure Under Fire

Due to its many advantages,steel structures are more and more widely used in China's building structure engineering.However,due to the poor fire resistance of the structural steel,the mechanical properties of the steel will decrease significantly with the increase of temperature in the event of fire,which will cause the steel structure to be seriously damaged under fire.Therefore,it is of great significance to study the mechanical behavior of steel structures under fire.Domestic and foreign scholars have carried out a large number of fire resistance tests and theoretical studies on individual components of steel structures and have achieved a series of results.However,in the actual fire,it is found that the overall mechanical properties of the building structure are very different from the mechanical properties of the single-members under fire.This has attracted the attention of researchers at home and abroad.In recent years,the overall performance of the structure under fire has been studied.Full attention has been paid to a large number of experiments and numerical simulations,but these studies do not give a systematic theoretical explanation.In this paper,the comparative analysis of finite element numerical calculation and first-order theoretical calculation is carried out to study the mechanical behavior and causes of steel frame structure under fire.The main research contents of this paper are as follows.1.According to the change of mechanical properties of steel under fire,the theoretical calculation formula of steel frame under fire is derived according to the first-order analysis theory.The internal force redistribution of steel frame during fire is analyzed,and the mechanical behavior of steel frame under fire is inferred.2.Using the model determined in this paper,the finite element numerical analysis method is used to simulate the mechanical behavior change trend of steel frame structure in the whole process of fire.According to the theoretical formula,the mechanical behavior of steel frame under fire is systematically analyzed.3.Further analysis of the mechanical behavior of a single-span single-span steel frame structure under fire to a multi-story multi-span steel frame fire.The mechanical behavior of the overall steel frame structure under different working conditions is studied,and the qualitative analysis of the multi-span multi-span numerical simulationresults is carried out by the above theoretical derivation results,in an attempt to improve the general test results and numerical simulation analysis of the general overall frame structure fire.System theory explains this status quo.4.Based on the above numerical analysis results,the effects of axial constrained stiffness,rotational confinement stiffness,high span ratio,large load,load type and other parameters on the mechanical behavior of the frame beam are analyzed.