Numerical Simulation On Earthquake Collapse Process Of Steel Frame Strucutre And Responses Of Its Ruins In Aftershocks

With the rapid development of urbanization and economization,steel structure is becoming the main structure form of urban buildings,especially important buildings.Although the seismic damage at home and abroad shows that steel structures have better seismic performance than masonry and concrete structures,the collapse of steel structures was found in the Northridge earthquake in 1994 and the Hanshin earthquake in 1995.It is of great significance to study the collapse mode of steel structures and the response characteristics of the collapsed ruins under strong aftershock.In this paper,the factors that influence the collapse mode of steel frame structures are discussed through numerical simulation analysis of typical steel frame structures.The survival space distribution of the steel frame ruin model with floor slab,partition wall and interior gallery is discussed.According to the needs of earthquake site ruins rescue,the safety conditions of building ruins and rescue access are studied.The main works of this paper are as follows:1.By introducing and comparing the relevant analysis methods of structural collapse,the analysis method selected for numerical simulation in this paper is determined.The key problems of parameter setting in the simulation analysis of structural strong nonlinear collapse are discussed,and corresponding solutions are given.2.Starting from the actual engineering background,an explicit dynamic analysis method was used to comparatively analyze the pure steel frame,the steel plate with floor and partition walls,the two steel frames,the steel frames with different axial compression ratios,and the steel frame with inner gallery,etc.For the collapse modes of structures under different working conditions,related factors affecting the collapse modes of steel frames are discussed.3.Through section analysis of the building ruin model,according to the distribution of the internal survival space,the distribution law of the survival space is initially given;through the numerical simulation results of structural collapse,it is found that when different types of steel frame structures collapse,due to The stiffness in the Y direction is greater,the X direction is weaker,and its collapse is all in the X direction.The presence of floor slabs and partition walls and the increase in number of tiles can significantly improve the collapse resistance of the structure and effectively reduce the damage of the structure under the action of strong earthquakes.After cutting the building ruin model,it is concluded that the survival space is mainly distributed in the narrow triangular space under the beam,column and beam plate,and the corresponding earthquake evacuation and rescue suggestions are given for the corresponding survival space.4.Realized the start-up analysis of the ruin weight of the collapsed ruins of a typical steel-framed house structure with infill walls under strong aftershocks;preliminary study on the feasibility of setting up life-saving channels in the ruins of the steel-frame structure,by setting up typical rescue supports in the ruins,Analyze and discuss the effect of rescue support on the secondary collapse mode of the ruins;establish an equivalent simplified mechanical model for the safety judgment of the semi-inclined building ruins under the aftershock,and derive a semi-inclined steel frame with a certain inclination angle to the ground The critical PGA discriminant formula for the second collapse of the structural ruins under the aftershocks is deduced,and the safety discriminating method of the rescue channel support is derived.Taking the example in this paper as the object,the critical PGA relations of the secondary collapse aftershocks corresponding to different slopes of typical semi-tilted ruins are given respectively.