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Accounting for Emergency Response in Building Evacuation: Modeling Differential Egress Capacity Solutions.


pdf icon Accounting for Emergency Response in Building Evacuation: Modeling Differential Egress Capacity Solutions. (158 K)
Averill, J. D.; Song, W.

NISTIR 7425; 13 p. April 2007.

Keywords:

evacuation; egress; emergencies; response time; fire fighters; first responders; stairways; occupants; evacuation time; stairwells; simulation; fire drills; office buildings; high rise buildings; equations; validation; scenarios

Abstract:

The impact of firefighter response on the progress of the building evacuation is not typically considered. Responders use of the stairs while occupants are evacuating can significantly increase total building evacuation time. To account for emergency response, this analysis considered whether adding. capacity through extra stairwell width was equivalent to providing the same total egress capacity through an additional stairwell. An egress simulation with a counterflow submodel was calibrated against recent fire-drill experimental results to demonstrate the capability of the model to produce meaningful evacuation results. The model was then applied to a hypothetical 50 story office building with 350 occupants per floor. When comparing equivalent total width, additional stairwells outperform wider stairwells from the perspective of evacuation performance, as well as firefighter ascent times. A third stairwell can completely mitigate the effect of firefighter response or even improve the building evacuation time compared to two stairwells with no firefighter response. Background: The ICC Terrorism Resistant Buildings (TRB) Committee has proposed a change to Section 403 of the International Building Code (IBC), which would require one additional stairwell (one greater than otherwise required) for all high-rise buildings (other than R-2) taller than 420 ft (128 m). The proposal would provide greater egress capacity than currently required, recognizing that one stairwell may become unusable during evacuation due to the introduction of smoke and heat and blockage by fire hoses once suppression operations begin. Objective: Perform computer egress modeling to provide quantitative comparisons of different stairwell configurations with and without emergency response interaction. Model Description: The computer model is a modified form of a biased random walk model without back step. The model is defined in a two-dimensional grid, of which each site can be occupied by a pedestrian or be empty. Each pedestrian can move to a neighboring site with certain probabilities. Usually, every pedestrian has a drift to move to the preferential site. All the possible configurations of downward walkers are demonstrated in Figure 1. The movement probabilities can be calculated with Equation 1.