Research On Smoke Diffusion And Evacuation During Construction Of Main Structures Of High-rise Buildings

With the rapid development of the national economy since the reform and opening-up of China in the past forty years,the construction scale and quantity of high-rise buildings have been increasing in China.When high-rise buildings once in the event of a fire,it will cause serious casualties and significant property damage.The high-rise building fire cases in various countries have been frequently repeated year after year.Although foreign experts and scholars have been doing a lot of effective theoretical and experimental research on fire smoke and evacuation of high-rise buildings that have already been built,But only few researches on smoke regulations and evacuation in the event of a fire in construction period of main structure.This is a great practical significance to study such issues.When fire happening in the construction period of the main structure of high rise building.The smoke of the fire spread across the room of the floor,Smoke exhausting only depends on the structure of the high-rise building itself.The diffusion of smoke in the staircase and the elevator well is complicated and changeable,It is necessary to establish a precise field model for fire simulation in the study of such problems.Pyro Sim,fluid dynamics fire software is used to simulate the fire smoke flow across the world in this paper.On the research of the theory of fire smoke movement in the construction site of high rise building and the analysis of all kinds of possible fire risk factors in the construction,The physical model of a high-rise residential building which has been constructed to eleven floors has been built by Pyro Sim software.The characteristics and flow of smoke at the location of ignition source at the first and five floors are obtained.And set the same wind direction in different speed,under different wind direction in same wind speed,the smoke changes of temperature,flow velocity and carbon monoxide concentration at different positions.1.when the ignition source is on the first floor and 20 seconds after the fire,The smoke spread through the well,the elevator well and the equipment well to the eleven storey construction area,Endangering the safety of the builders at the eleven level.Under the effect of chimney,The speed of the smoke flowing upward in the well,the elevatorwell and the equipment well is very fast and speed up to 5.7m/s.The temperature and carbon monoxide concentration are also relatively high in the shaft structure,but smoke in the staircase is relatively slow and the speed is 1.86m/s.2.When the ignition source is on the fifth floor,Smoke is less affected by the floor below the fire source,The velocity,temperature,and carbon monoxide concentration at the upper floor are changed.3.The smoke under the influence of different wind speeds in the direction of the north side.When the wind speeds up,The lower temperature of the smoke in the area near the fire source and the faster the smoke movement,The concentration of carbon monoxide in the staircase will decrease.4.Then the smoke under different wind direction with same speed is studied,The influence of outdoor wind on the smoke velocity at the staircase of the simulated building is the north wind > the south wind > the west wind,Under the west wind carbon monoxide concentration is the highest in staircase and corridor,Under the north wind carbon monoxide concentration decrease obviously,The influence of outdoor wind on the regional temperature changes near the fire source is west wind > north wind > south wind.5.Finally through the safety evacuation simulation software Pathfinder,The evacuation conditions and various factors are used in the evacuation model is established in the construction site.Simulation of evacuation time of workers in buildings under different fire conditions,The result shows that the different choice of the safety exit of the builders and under different fire conditions,which will directly affect the evacuation lines and the whole evacuation time.The research on the characteristics of fire smoke flowing in the construction period of the main structure of the high rise building and evacuation of persons in this paper provide theoretical basis and reference for the fire prevention,fire emergency response plan and safety evacuation.