Abstract: A high-rise office building was selected as the research object, and a fire diffusion model was established by using PyroSim to calculate the available safe evacuation time when the 25-story corridor catches fire. The Pathfinder was used to establish an evacuation model and calculate the required safe evacuation time. The influence of mixed evacuation strategy on evacuation efficiency are analyzed. The results show that: Compared with temperature and CO concentration, the time for visibility to reach the safe evacuation limit is shorter. When the 25th floor corridor is on fire, the available safe evacuation time of the fire floor under the most unfavorable conditions is 319.1 s. The required safe evacuation time of stair evacuation strategy and the mixed evacuation strategy of stairs and elevators is 526.3 and 427.9 s respectively, which do not meet the safe evacuation conditions. The required safe evacuation time of the mixed evacuation strategy of stairs, elevators and refuge floors is 294.2 s. It takes 2 618 and 2 289 s to evacuate the whole building with stairs strategy and the mixed evacuation strategy of stairs and elevators. It takes 1 796 s to evacuate the whole building by mixing the stair, elevator and the refuge floors. Therefore, it is more efficient and safer to use the mixed evacuation strategy of stairs, elevators and refuge floors in high-rise building fire. The research results provide a basis for formulating emergency evacuation plans for high-rise office buildings.

Key words: high-rise office building, mixed evacuation, PyroSim, Pathfinder, security analysis