Abstract
This paper assesses the evacuation time for a 25-storey office building. The scenario modelled assumes that a fire has arbitrarily taken place at Level 11, and a whole-building evacuation is required. The evacuation will be via a phased evacuation strategy utilising the stairs for those who are able to self-evacuate, and evacuation lifts for those who are unable to self-evacuate by stairs. The stair widths have been designed to be compliant with BS 9999 recommendations. The lift evacuation strategy is operator assisted evacuation operation.
To determine the suitability of the evacuation strategy, a comparative analysis of stair evacuation times against the total lift evacuation times is undertaken.
As a base design assumption, the building is provided with two escape stair cores and one evacuation lift per escape stair core. The proportion of users who are likely to require the use of the lifts for evacuation has been taken as 15% in line with the Department for Work and Pensions family survey information.
Initial findings indicate that the estimated stair evacuation time, when calculated in line with PD 7974-6, is approximately 53 minutes, while the lift evacuation time extends to approximately 3 hours and 53 minutes. The initial calculation results indicate a significant disparity in evacuation time, which would likely raise concerns with the available evacuation lift capacity in line with the Fire Strategy requirements and other human factors.
This paper aims to explore strategies for providing lift evacuation times more in line with the stair evacuation times and enhancing overall evacuation efficiency.