An investigation of fire evacuation performance in irregular underground commercial building affected by multiple parameters

Irregular underground commercial buildings (IUCB) are difficult to evacuate because of large space depth, complex form changes, and dense crowd. Fire evacuation performance of IUCB is of great practical importance with the development of underground buildings. To analyze the influence of different evacuation parameters on the properties of IUCB fire evacuation, this research gives person evacuation time under different strategies, action time of agent, and evacuation time based on IUCB fire evacuation numerical analysis model. A virtual reality system (VRS) including testing equipment and record platform is designed to perform model validation. Influence of three parameters are also analyzed on the performance of IUCB fire evacuation, including evacuation numbers, minimal group effect and pre-action time. Social force model and Generalized random graph model are applied to behaviors of evacuee. The results show that crowd congestion becomes a key factor determining evacuation time after the number of evacuees’ increases by 50.0%. The unbalanced use of exits reduces the overall evacuation rate. The average evacuation time, the overall evacuation time, and the total evacuation time of 95.0% population increase by 13.3%, 36.0%, and 15.9% respectively. When 50.0% of the evacuees are set as the minimal group effect, the overall evacuation time increased by the minimal group effect aggravates the congestion in some routes, but the minimal group effect could reduce the long tail time. Reducing the pre-action time can improve the overall evacuation rate in the early stage of evacuation. The basic linear relationship between pre-action time and evacuation time is presented. This research can provide the guidance for exit fire evacuation for IUCB to be built, which can also reduce the evacuation time in fire evacuation.