Research On Fire Smoke Simulation And Evacuation In Atrium Teaching Building

An atrium is a kind of large space building without intervals in the building of two or more stories. With its visual impact and beauty, atrium buildings have been increasingly applied in teaching buildings of many universities in China and become the trend of construction in many cities. As atrium buildings develop rapidly, the occurrence of fire is on the increase correspondingly. Meanwhile, when fires occur in atrium buildings, the smokes diffuse quickly, fire spreads quickly, few emergency exits are available and the internal flow density is large; therefore, disastrous consequences would be produced in atrium buildings once a fire takes place. At present, although China has formulated and implemented regulations on smoke control and evacuation in atrium buildings, it is not sufficient to catch up with the rapid development of new-type buildings because of certain irrationality in those regulations. Therefore, with the flourishing of atrium buildings, current fireproofing and smoke bays are facing challenges, and it is also urgent to study on smoke spread process and evacuation countermeasures in atrium buildings.This paper mainly investigates the principles of smoke spread and diffusion, analyzes factors that influence people’s safe evacuation, and evaluates and solves safety problems when the atrium buildings are on fire. In recent years, studies concerning on building fires have focused on only fire smoke or evacuation respectively, and then conducted safety assessment by comparing with related safety standards. Instead, this paper conducts researches by combing smoke spread process with personnel evacuation through numerical simulation.This paper firstly elaborates domestic and overseas researches on smoke, personnel evacuation and fire simulation techniques in atrium buildings, and briefly introduces research contents, methods and theoretical basis of fire simulation. Secondly, using the modeling software-Pyrosim, this paper establishes a3D Fire physical model. Besides, by using fire dynamics simulation software FDS5.0to conduct smoke numerical simulation in atrium buildings of a university, this paper studies the smoke spread, temperature distribution, poisonous gas concentration and visibility in atrium buildings when fires take place in different sites under two extreme cases, from which the evacuation time is worked out. Meanwhile, in order to study the smoke flowing rules of natural smoke vents in atrium buildings under two extreme cases, this paper selects the most dangerous site in the building and designs two fire source scenes accordingly, which are in the corridor or atrium (outside the room) and inside the room. The simulated results indicate that:(1) When atrium teaching buildings are on fire, the main factor that influences personnel escape is visibility.(2) When the fire source is inside the room, smoke temperature, poisonous gas concentration and visibility change more slowly than those when the fire source is outside the room, and the influence of smoke on staircases is relatively small. (3) The atrium fire is the mot dangerous. When it happens, we must devise and organize the reasonable personnel evacuation route to ensure the safety of people.This study also makes a simulative analysis of the evacuation process in the teaching building by using directed and undirected evacuation models as well as the evacuation simulation software Pathfinder, from which the essential safe evacuation times of two evacuation models are obtained. By comparing the two evacuation models, it is concluded that:(1) Directed evacuation can optimize the evacuation flow of each floor and reduce the evacuation time by112s in the fixed building condition.(2) During the evacuation, it takes relatively short time for people to evacuate from the room; however, queues and concentration of personnel take place near the staircase, and the stairs are blocked up, and thus the evacuation time is lengthened.Finally, when the natural gas vent is under two extreme cases, the fire risk times gained by various fire scenes are respectively compared with the essential safe evacuation times obtained from different evacuation models. This study then makes a fire risk assessment of atrium buildingsby combining all kinds of factors and finds out key factors for building fires and safe personnel evacuation. In addition, this paper also puts forward feasible fire prevention measures and evacuation schemes. The research results confirm that:natural smoke vent condition and personnel evacuation model are the key factors for safety personnel evacuation when the building is on fire; different evacuation methods have much more influence on the construction security when the natural smoke vent is closed,and only ordered evacuation can ensure the safe evacuation of personnel. When the rooms,corridors and atrium’ natural smoke exhaust tunnel opens with an orderly evacuation, it will significantly improve the safety of the building from fires.The research results in this paper can be used for certain reference and guidance for smoke spread and control, evacuation and performance-based fire safety designin similar buildings.