| At present,with the rapid development of urbanization in China,the subway rail transit in the city is developing rapidly,and the subway line is gradually showing a grid operation mode.Due to the advantages of low cost,fast construction and beautiful appearance,elevated subway stations are often used in the construction of urban subway network in many suburban areas of large and medium-sized cities in China.Compared with the common deep underground subway station,the internal spatial structure of elevated subway station has the characteristics of open and large space.This paper summarizes the fire cases of major subway stations in China and abroad,and based on the elevated subway station model,mainly explores three aspects :1)Building the elevated subway station model by FDS software。And consult relevant literature,as well as subway fire protection design standards and other relevant specifications,calculate and design elevated subway station natural smoke exhaust shutter height size of 2.4m.Combined with the numerical simulation of the code and the actual control,the design height of 2.2 m smoke retaining wall is designed to effectively limit the migration of smoke in the station hall during a period of time after the fire.According to the specification,the total rate of mechanical smoke exhaust in the numerical simulation model is set to be 28 m3 / s,and the most unfavorable ignition point for evacuation in the model is selected by comparing the fires at different locations.Finally,the ventilation mode of natural exhaust + mechanical exhaust was determined for the model.2)The stability and longitudinal temperature change of smoke layer under the influence of smoke spread and settlement in different common fire source fuels of elevated subway station.The research on flue gas thermal stratification in narrow and limited space such as tunnels is combined with flue gas spread in elevated subway stations.Pyrosim software was used for modeling of elevated subway stations and numerical simulation under a large number of different working conditions.The concept of stratification intensity was introduced to measure the temperature of flue gas under different fuel combustion conditions.The variation of flue gas temperature with time was obtained and calculated theoretically.The obtained results were analyzed and fitted by SPSS software.The Logistic model and Boltzmann model were successfully fitted,and the final fitting coefficients were higher than 0.99.3)Referring to the factors of personnel behavior in the safety evacuation specification,and using Pyrosim for numerical simulation,the required safety evacuation time t B of personnel under different fire locations and different mechanical smoke extraction rates is calculated by software.Pathfinder is used to build a three-layer model of the elevated subway station model in Pyrosim,and the number and behavior data of different age ratios are set to calculate the available safety evacuation time t A of personnel under different personnel densities and different working conditions.The concept of evacuation reliability is introduced,and a large number of independent repeated simulations are carried out on the cases.Finally,the probability of t A < t B is calculated by using the data analysis software SPSS,and the improvement of evacuation reliability by mechanical smoke exhaust is calculated,as well as the measures that can be improved in the evacuation of similar model fire scenarios of elevated subway stations.In the similar model of elevated subway station,the smoke retaining wall is set up,and the smoke prevention and exhaust mode of natural smoke exhaust is given priority to,and mechanical smoke exhaust is supplemented can optimize the evacuation mode effectively. |
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