Study On Natural Ventilation And Smoke Prevention Of Refuge Floor In Super High-rise Office Building Based On FDS

According to China’s Code for Fire Protection in Building Design GB50016-2014(2018Edition),a refuge floor(room)shall be set for public buildings with building height greater than 100 m.Refuge floor set purpose is to make staff in the event of a fire with a safe refuge and wait for help,therefore,refuge floor in high-rise building fire prevention and control plays an important role,so the research on the refuge storey super-tall office building natural smoke prevention smoke evacuation conditions for fire safety prevention and control is of great significance.In this paper,the fire dynamics software FDS was used to design 110 fire conditions in a32-story office building with a height of 126 meters as the physical model and the refuge floor as the research object.Numerical simulation was conducted on the smoke prevention effect of the refuge floor under the natural ventilation mode by changing the window-ground ratio of the refuge floor.Thus,the critical window-ground ratio can be obtained under different fire power,fire location,environmental wind direction and wind speed.The results show that:(1)Under the condition of no environmental wind,when the fire source is set in the lower floor of the asylum floor and the power of the fire source is 1.5MW,the critical window-ground ratio of the asylum floor is 12%.When the power of fire source is 6MW,the critical window to ground ratio is 15%,which can ensure that the refuge layer can maintain the safety refuge requirements during the safe evacuation time.It is also found that the larger the power of the fire source is,the farther the fire source is from the refuge layer,and the larger the critical window-ground ratio of the refuge layer is.(2)In the natural ventilation mode of refuge floor,when the environmental wind speed is4m/s and the fire source power is 1.5MW,the critical window-ground ratio of refuge floor is7%;when the fire source power is 6MW,the critical window-ground ratio is 9%;When the environmental wind speed is 8m/s and the fire source power is 1.5MW,the critical window-ground ratio of the refuge floor is 5%;when the fire source power is 6MW,the critical window-ground ratio is 8%,which is most conductive to the natural smoke prevention of the refuge floor and the evacuation and fire rescue of personnel when the fire occurs.It is also found that the higher the power of fire source is,the lower the wind speed is,and the larger the critical window-ground ratio of refuge layer is.(3)It is found that with the change of environmental wind,the visibility and temperature of flue gas in asylum layer will also change greatly.In the presence of environmental wind,the critical window ground ratio of refuge layer decreases obviously.(4)Based on the analysis and conclusion of this paper,considering the actual wind speed at the height of refuge floor is generally 8m/s and above,it is suggested that in the natural ventilation mode of refuge floor,the critical window to ground ratio should be modified from2% in the current Technical Standard for Building Smoke Control and Smoke Exhaust System to 8%,and Windows should be arranged in different directions as far as possible.In mechanical smoke control mode,the critical window ground ratio is changed from 1% to 4%.The conclusions obtained in this paper can be used to optimize the natural smoke exhaust design of the refuge floor.During the building planning,the window area of the refuge floor should be set according to the relevant building fire prevention regulations and the local dominant wind,which will be more conducive to protecting the personal safety of the refugees from threats in case of fire.