Seismic Analysis Of Multilayer Steel Frame After Fire

Steel structure is widely used in the construction industry due to its advantages of light weight,high strength and easy construction,while mechanical properties of which such as elastic modulus,yield strength drops rapidly at elevated temperature.The bearing capacity of some members of the steel structure is lost to some extent or even completely destroyed after localized fire,but the main structure does not collapse and can be reused after repair.Repair of post-fire steel structure can reduce steel loss,bring huge economic benefits,but there have been short of systemic research on the seismic performance of post-fire steel structures,which limits the extension of post-fire repair of steel structures in high-intensity areas,so the research on seismic performance of structure after fire is very essential.At present,the researches on seismic performance of post-fire structures focus on nodes,columns and planar frames,which cannot reflect the influence of structural internal force redistribution on structures during fire.Therefore,three-dimensional structure is adopted in this paper to analyze the seismic performance of structures after fire.The main contents of this thesis are listed as follows:1.Assuming that the fire area is limited to the corner room,side span and the whole first floor,the collapse analysis of steel structure exposed to fire is carried out to reveal the influence of fire location on the structure collapse.Based on the results of collapse analysis,the whole process of fire was analyzed to study the internal force,displacement and plastic development of structure in the process of fire.2.Hysteretic analysis of the post-fire frame to obtain the hysteretic curve and skeleton curve of the beam-column joint,and the influence of fire on the stiffness and energy-dissipating capacity of the joint is analyzed.3.Dynamic time history analysis under the action of frequent and rare earthquakes is carried out to obtain the stress,base shear and inter-story drift to investigate the influence of fire on dynamic response of structure,and the failure mechanism and plastic development of structure under rare earthquake are studied.