Research On The Coupled Model Of Underground Garage Fire And People-vehicles Mixed Flow Evacuation

With the progress of urbanization,the design and application of underground parking lots have become more complex.Due to the enclosed space of underground parking lots,fire protection and safety evacuation are difficult.Once a fire occurs,it can easily cause serious losses and injuries.In traditional building fire protection design and safety research,fire and evacuation simulations are usually independently conducted,using pedestrian necessary and available safe evacuation time to determine safe evacuation conditions.Traditional methods cannot reflect the impact of fire spread on pedestrian evacuation,and the interaction between pedestrian and vehicle evacuations within underground parking spaces makes fire evacuation simulation even more difficult.This article takes the underground parking lot of a commercial complex in Xi’an as an experimental and simulation object.Based on the cellular automaton theory,background field model,and fire field model,the space model,fire model,pedestrian model,vehicle model,mixed pedestrian-vehicle evacuation model,and fire evacuation coupling model are constructed using Python language and PyroSim simulation,achieving the coupling simulation of fire and evacuation processes,and building a preliminary real-time simulation system for dynamic simulation of pedestrian-vehicle mixed-flow evacuation under fire conditions.Based on the simulation results,quantitative evacuation parameters can be obtained to improve building safety design and optimize evacuation plans.The overall conclusions are as follows:(1)Site experiments on pedestrians and vehicles in the underground parking lot.Combining the building plan design and structural measurements,the spatial parameters of the site are obtained,and an equidimensional model is constructed.The results of daily and emergency speed experiments,the most unfavorable pedestrian and vehicle evacuation times,and the analysis of evacuation experiment images are used to obtain the trajectory rules of pedestrian and vehicle evacuation times.(2)Simulation and analysis of mixed pedestrian-vehicle evacuation.The pedestrian,vehicle,and mixed pedestrian-vehicle evacuation models are constructed.Combined with the results of on-site evacuation experiments and model simulations,the time coefficient ω is used to correct the evacuation model to obtain the most unfavorable single pedestrian and vehicle simulation evacuation time.Quantitative parameters such as pedestrian and vehicle density,evacuation trajectory,and evacuation time are analyzed to evaluate underground parking lot evacuation strategies,improve building design and evacuation plans.(3)Fire simulation and acquisition of smoke characteristics data.PyroSim simulation software is used to arrange smoke temperature,CO concentration,visibility measurement points,and slices at the ceiling and personnel characteristics.The tolerance critical value of pedestrians is analyzed,the fire hazard status is judged,the available and necessary safe evacuation times for pedestrians are compared,and the safety of building design is evaluated.(4)Research on the coupling simulation of emergency evacuation during fires.The fire spread data is obtained through PyroSim monitoring equipment,and the fire and evacuation data are coupled using interpolation algorithms.The transfer probability,pedestrian health index,and parking rules in the background field model are extended,and a dynamic coupling model of fire and mixed pedestrian-vehicle evacuation is established.When the evacuation start time exceeds 200 s,pedestrian evacuation failure exists,and countermeasures for underground parking lot emergency evacuation can be analyzed based on the simulation results.