A New Method for Estimation of Staircase Evacuation Time in High Rise Buildings

Abstract

As cities become more modern and complex, safe building evacuation within the stipulated time during an emergency is one of the major challenges for building designers, building occupants and the government. The most important requirement is to achieve evacuation before tenability is reached, i.e. the RSET (Required Safe Evacuation time) should be less than the ASET (Available Safe Evacuation time). Generally, various evacuation components like staircases, evacuation elevators, sky bridges, fire escape chutes, and controlled lowering devices are available along with evacuation strategies like total evacuation, phased evacuation, stay in placed evacuation and delayed evacuation. However, total building evacuation using the staircase is the most accepted, safe and traditional method of evacuation due to the unexpected behavior of fire and occupants [1–3]. Additionally, to decide on the geometry of the staircase, it is very important to know the required time to evacuate the building, so that the evacuation strategy can be decided. The evacuation time depends on important building parameters like staircase width, the height of the building and the number of occupants. Studies made by Galbreath [4] and Pauls [5] have suggested a relationship between the rates of discharge, the flow of occupants, and occupant density for the calculation of evacuation time. They have suggested two different relationships for two different flows, i.e. free flow and congested flow at the stairs. In this paper, one hundred and twenty building models are studied with different parameters like width of the stairs, occupant load, number of the floors and area of floor with two main objectives. The first objective is to study the impact of various building parameters on the overall building evacuation process, and the second objective is to suggest a single relationship with all parameters considered, which can be applied to calculate evacuation time and to further decide the width of the staircase and the maximum allowed occupants load.