Simulation Research On Fire Accidents Of Medium And Low Speed Maglev Railway And Its Impact On Tracks And Its Lower Bridges

As a new type of urban rail transit system,the medium-and low-speed maglev railway has the characteristics of concentrated personnel and narrow space.Once a maglev train fires,it will pose a life threat to passengers in the train.When the underbody equipment layer is in fire,the components of the maglev track structure will be stressed and deformed by heat,which will affect the normal operation of the train.At present,most of the research on medium and low-speed maglev railway fires is concentrated in the interior of the train.There is no consideration of the impact of train equipment layer misfire and line side cable fire on line infrastructure such as rails and track beams.For the study of the temperature effect of the track structure,only the daily temperature difference is considered,and extreme conditions such as fire are not considered.Based on the "Key Technology of Emergency Rescue on the Middle and Low Speed Maglev Railway Viaduct" funded by the Beijing Natural Science Foundation(8172040),this paper develops a simulation of the maglev railway fire based on the basic theory of fire science and the composition of the medium and low speed maglev railway system.Impact on the track and its underlying bridges and line operations.For the internal fire of the train,the Pyrosim software is used to simulate the various working conditions.The results show that the visible distance reaches the critical point before the temperature of the flue gas;after the fire,the fan and the train side door can exchange the air in the cabin and the outside,effectively suppressing The temperature increase and the smoke diffusion,the effect increases with the increase of the fan speed;based on the analysis of the simulation results,the emergency treatment plan for the cabin fire is proposed.For the train equipment layer and evacuation platform cable fire,the temperature of each position of the track structure was simulated by Pyrosim software.The finite element heat transfer model and the thermo-mechanical coupling model of the track structure were established by using ABAQUS software,and the fire simulation results were input into the model for transient analysis.Obtain the temperature field of the track structure and its stress and deformation during fire.The results show that when the train equipment layer is in fire,the F-rail,steel pillow and other components rapidly heat up and generate stress and deformation.When the heat release rate of the fire source is 5MW-30MW,the vertical displacement difference between the inner and outer magnetic pole reaction surfaces of the F-shaped guide rail exceeds the specified limit.The value affects the normal running of the train.It is recommended to raise the bolt grade appropriately.According to the time-varying law of the track structure deformation,the concept of the fire limit time is proposed,and the curve of the fire limit time with the heat release rate of the fire source is obtained,and the train fire emergency disposal plan is adopted.Make a reference suggestion.For the fire under the track beam bridge,the Pyrosim software is used to simulate the temperature field of the two-track box beam and the juxtaposed single-line box beam.The two-line box girder is used as an example to calculate the heat release rate of different fire sources using ABAQUS software.Stress and deformation of the track beam at the time of fire source distance.The results show that the temperature distribution of the two track beams is basically the same,but the fire zone of the double-line box girder is larger than the juxtaposed single-line box girder;the deformation of the box girder increases with the increase of the heat release rate of the fire source and the decrease of the fire source distance.Large,top and bottom plate deflections reach the specified limit within 30min,affecting the geometry of the maglev line and the safety of the train;continuous combustion will cause damage to the track beam within a certain period of time;based on the simulation results,it is recommended in the fire hazard area Apply fire-resistant paint or take reinforcement measures,and propose the best time for line outage and fire suppression in different situations.This article has a total of 176 figures,20 tables,87 references.