Research On The Fire Analysis And Numericial Simulation In High-rise Building Under Construction

With the rapid economic development in China,the accelerating urbanization process and the increase in the number and height of the high-rise buildings have made high-rise buildings more and more difficult to build.Fire accidents pose a great threat to the safety of life and property.Compared with the existing high-rise buildings,abuilding high-rise buildings have a long construction period,many joint participants and complex working interfaces,resulting in more fire safety hidden dangers.Considering the characteristics of fire burning in high-rise buildings under construction,the combination of theoretical analysis and numerical simulation is of great theoretical significance and practical value for preventing fire and rescue work in high-rise buildings under construction.The main contents of the article include the following aspects:First,according to the characteristics of the fire in the high-rise buildings under construction,the theoretical basis of the fire flashover and chimney effect was determined.By describing the motion state,critical condition and criterion of smoke in flashover,the nonlinear analysis method of flashover is introduced.The chimney effect was classified;the pressure distribution of the flue gas in the shaft was analyzed,and the neutral Klote model of the shaft was described.Secondly,the catastrophe study of fire flashover in high-rise buildings under construction.Established the energy conservation equation of high-rise buildings under construction.After dimensional normalization and differential homeomorphic transformation,the potential function which belongs to the swallowtail catastrophe was obtained.According to the control variable bifurcation set curve of the catastrophe system,the critical temperature of the upper layer of flue gas was calculated when the building fire broke out.Third,built the calculation model of the vertical shaft temperature and neutral surface of the high-rise buildings under construction.By analyzed the upper opening and lateral continuous opening vertical shaft characteristics of the high-rise buildings under construction,the vertical temperature model was deduced for the characteristics of the flue gas.According to the characteristics of continuous distribution of the temperature in the shaft,the neutral model of the shaft was established.The results of the analysis and research obtained the influencing factors of the chimney effect.Finally,a fire numerical simulation model for high-rise buildings under construction was established.Simulated software FDS was used to simulate fire in different construction scenarios of high-rise buildings under construction,and the fire characteristics such as fire heat release rate,temperature,smoke visibility,and CO concentration were analyzed for different combustibles,different ventilation wind speeds,and different fire source locations.The law of change verified the phenomenon of fire flashover and chimney effect.