I am using Pathfinder to determine the maximum number of people that can be permitted in the top most storey of a building to be able to achieve safe evacuation.
In doing that I built a base model of the building and varied the number of occupants in the storey of interest ranging from 200 to 300 people in that storey.
Based on the results of the evacuation model, the overall evacuation time is shorter for 200 people while 300 people require more time to fully evacuate which makes sense.
However, 250 people require longer time (approx. 6 seconds more) to complete evacuation when compared to 260 people and I initially thought it must have something to do with the minimum distance between the occupant and the nearest exit. Because, with the increased occupant density, minimum distance reduces leading occupants to be located closer to the exit.
However, upon taking a closer look at the results summary file, the difference in travel distances does not appear to be significantly larger (approx. 0.4 m lesser than 250 people).
To further add to this, I did cascade sequence (i.e. set an initial delay time) for the occupants in the lower storey to begin evacuation at a later stage. Based on the results of the maximum distance travelled by any occupant in the storey of interest is 2.4 m longer for 250 people when compared to 260 people for one particular scenario with a 2-minute delay time. For the other scenarios with no delay, 1 minute delay and 3-minute delay times, the difference in maximum distance is 0.6 m, 0.2 m, and 0.2 m respectively.
I am trying to understand why there is a change in the maximum travel distance because the model is exactly the same with the same number of occupants and the only change in the models is the delay time to begin evacuation. And trying to understand why the evacuation of 260 occupants is quicker than 250 occupants.
If someone in this forum could help me in understanding the logic behind the obtained results, it will be greatly appreciated.
Please send an example model to email@example.com for closer examination.