Failure Mechanism Analysis Of RC Frame Structures Under Post-earthquake Fire

After the earthquake,secondary fire has become a major threat and disaster faced by buildings.The occurrence of earthquakes and fires are both small probability events.However,once an earthquake occurs,the secondary fire is one of the secondary disasters with the highest probability.The casualties and property losses caused by post-earthquake fire are sometimes far greater than those caused by the earthquake itself.At present,scholars at home and abroad have carried out extensive research on seismic performance and fire resistance of building structures,but there are few researches on the structural response under combined action of earthquake and fire.Concrete frame structure is one of the most widely used structures in modern engineering construction.It is necessary to study its structural performance under the combined action of earthquake and fire.Because there is a big difference between the thermodynamic properties of steel and concrete,with the earthquake structure deformation,internal force in the structure under the action of secondary fire distribution is complex.And there is no mature analysis method,so the research of the fire resistance performance of RC frame after the earthquake is still in the initial stage.Based on a large number of finite element model analysis,the redistribution of internal force and fire resistance of RC frame under the combined action of earthquake and fire are studied.The main research contents are as follows:(1)Based on the ABAQUS finite element software platform,the RC framework model is established under the combined action of earthquake and fire.Compared with the temperature rising curves and lateral force displacement curves obtained by the two tests,the rationality and applicability of the model are verified.(2)The combined effect of the earthquake fire model established in this paper and compared with the only fire model of local fire conditions,different fire position on the influence of frame internal force redistribution,including single column under fire,the three face under fire,surrounded by fire,and the top surface of the beam under fire,at the bottom of the the fire,the beam and the column under fire and other local fire situation.The redistribution of internal force under the combined action of earthquake and fire of RC frame is studied and compared with the case of fire alone.(3)The combined effect of the earthquake fire model established in this paper,in-depth analysis of the fire mode under constant temperature,and the effect of degradation and redistribution of internal force of the bearing capacity of concretemembers subjected to fire time of different temperature,and compared with the fire alone model.In addition,the influence of axial compression ratio on the fire resistance limit of RC frames under different earthquake magnitudes is also discussed.