Study On Natural Smoke Prevention Of Staircase And Independent Front Room Of High-rise Office Building Based On FDS

High-rise office buildings with a building height of no more than 50m are not only an important part of urban buildings,but also an important place for people to work and live together.Their independent front rooms and staircases mostly adopt natural smoke prevention methods.In case of fire,the independent front room and staircase are the main channels for personnel to escape.Due to the spread of smoke in case of fire,visibility will be reduced,CO concentration will increase and temperature will rise,which is easy to cause casualties of escape personnel.Therefore,it is of great significance to study the natural smoke prevention of the independent front room and staircase of high-rise office buildings with a building height of no more than 50m.In this paper,FDS software is used to simulate two office buildings with a floor height of4 meters,12 floors and a total of 48 meters.Taking the height of the window in its independent front room from the ground,the window area and the window position in the stairwell as the research object respectively,better optimization suggestions are put forward by analyzing the parameters such as smoke spread,visibility,CO concentration and temperature.The first case is the study of independent anterior chamber windowing.According to Article 3.1.3 of Technical Standard for Smoke Management System in Buildings(GB51251-2017)(hereinafter referred to as the Smoke Standard),for public buildings with a building height of less than or equal to 50m,when the independent front room meets the requirements of two or more openable external windows with different directions,and the area of the two external windows of the independent front room is not less than 2.0m~2respectively,the staircase may not be equipped with smoke control system,the following conclusions are obtained after analysis:(1)The height of the independent front room window from the ground has a significant impact on its smoke prevention effect.The higher the window height from the ground,the better the smoke prevention effect,and the window is located under the beam;(2)The power of the fire source is 1.5MW.When the fire source is located on the first floor and the middle floor(6th floor),the windowing area of the independent front room described in article 3.1.3 of the Smoke Standard cannot ensure the safety of personnel evacuation in case of fire,so the area of each window should be expanded to 3m~2.When the fire source is located on the high floor(11th floor),the windowing area of the independent front room described in article 3.1.3 can ensure the safety of personnel evacuation;(3)The power of the fire source is 6MW.When the fire source is located on the first floor,middle floor(6th floor)and high floor(11th floor),the window area of the independent front room described in article 3.1.3 of the Smoke Standard cannot ensure the safety of personnel evacuation in case of fire.When the fire source is located on the first floor,the area of each window should be expanded to 4.6m~2,when the fire source is located on the middle floor(6th floor),the area of each window should be expanded to 3.8m~2,and when the fire source is located on the high floor(11th floor),the area of each window should be expanded to 3.2m~2.To sum up,the window area of two different directions of the independent front room is not less than 4.6m~2,and the window is located under the beam,which can meet the safety requirements of personnel evacuation.The second case is the study of the window opening position of the staircase.According to the article 3.2.1 of"when the building height is greater than 10m,openable external windows or openings with a total area of not less than 2.0m~2shall be set in every 5 floors on the outer wall of the staircase,and the layout interval shall not be greater than 3 floors",the windows shall be arranged(the windows are located on the 1st,2nd,6th,7th,9th and 12th floors,1m~2 per floor),and the fire source is located on the first floor.The window opening position on the first floor,non first floor and the overall consistent window opening position of the staircase shall be studied respectively.Through the full floor window opening of the staircase,the fire source is located in different positions for verification.After analysis,the following conclusions are obtained:(1)When the fire source is located on the first floor,the position of opening the window has a significant impact on the smoke prevention effect.If the window is located under the rest platform,the smoke prevention effect is the best;The window crosses the rest platform,and the smoke prevention effect is the second;The window is located on the rest platform,and the smoke prevention effect is the worst.When the fire source is located in the middle layer(6th floor)and the high layer(11th floor),the window position of the staircase has no significant impact on the smoke prevention effect,but the smoke prevention effect is still the best when the window is located under the rest platform.(2)The window opening position on the first floor of the staircase has an impact on the height of the smoke layer on the first floor from the ground.The window opening is located under the rest platform,and the height of the smoke layer on the first floor from the ground is the highest;The window crosses the rest platform,and the height of the first floor smoke layer from the ground is the second;The window is located on the rest platform,and the first floor is filled with smoke.