A Review of Building Evacuation Models - NIST Virtual Library
A Review of Building Evacuation Models - NIST Virtual Library
A Review of Building Evacuation Models - NIST Virtual Library
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density <strong>of</strong> the space and the capacity <strong>of</strong> the doors and stairways. The unimpeded walking speed<br />
for each occupant can be specified as a single number or a distribution can be specified for the<br />
population. The default mean, taken from Nelson and Mowrer, is 1.19 m/s with a S.D. <strong>of</strong> 0.2<br />
m/s and a minimum value <strong>of</strong> 0.3 m/s. Any specific number or distribution can be input by the<br />
user.<br />
Any amount <strong>of</strong> occupant groups or individuals can be defined by the user. Each individual or<br />
occupant group can have a set <strong>of</strong> characteristics. The characteristics were laid out in the<br />
Perspective section above. To reiterate, the characteristics <strong>of</strong> the occupant are:<br />
• xy coordinates <strong>of</strong> each occupant in time with the simulation<br />
• Starting position in the simulation<br />
• Destination/exit<br />
• Pre-movement time<br />
• Unimpeded walking speed<br />
• FED susceptibility (discrete value or distribution)<br />
Under smoke conditions, the occupants’ movement speed can vary according to their FIC for the<br />
irritant smoke. Also, depending upon their susceptibility, the occupants will be given a graphical<br />
hatched pattern in the scenario when their FED reaches 0.75. When they become incapacitated,<br />
FED=1, their 2-D image will turn black and they will stop movement.<br />
Also, overtaking <strong>of</strong> occupants can occur.<br />
GridFlow <strong>of</strong>fers multiple options for how merging flows are simulated 8 . The first option is the<br />
“free-flow” option, where flows are determined by the personal movement algorithms alone.<br />
When several inlets compete, the physical arrangement <strong>of</strong> the routes, widths <strong>of</strong> the links, and the<br />
crowd densities at the inlet and outlet decide the precedence. In the “controlled” flow option,<br />
additional rules are imposed on the competition. For example, when a stair with two inlets (flow<br />
from staircase above and current floor) is near or at maximum capacity, the outlet flow would<br />
balance to half from each inlet. Lastly, there is an option for assigning weights to certain links<br />
manually, so the user can control the dominance factor.<br />
Output: Output data can be exported from the model into an Excel spreadsheet. The range <strong>of</strong><br />
output include a details about the population in every space at every logging interval after each<br />
run and summarized data from a series <strong>of</strong> batched runs. The output also provides detailed<br />
aspects <strong>of</strong> the building and occupants (distributions <strong>of</strong> pre-movement, exit time, etc.).<br />
Use <strong>of</strong> fire data: No, but the model allows the user to come close to this. A spreadsheet can be<br />
established for every space in the building with 3 columns; time, speed factor, and FED dose.<br />
The time column is equivalent to the time monitored in the evacuation. The speed factor gives<br />
the ability <strong>of</strong> the user to decrease the speed by a fraction as the evacuation time increases, to<br />
simulate the influence <strong>of</strong> irritant smoke. If a 0.9 factor is input by the use at t=60 s, the<br />
occupants in the specific space will decrease their individual speed by 10 %. The last column,<br />
the FED dose, allows the user to input specific FED doses at different time intervals in the<br />
simulation. For instance, if 0.05 is input at 60 s and another 0.05 is input after 80 s, the<br />
individuals in that space will obtain an FED <strong>of</strong> 0.1 by 80 s. Within the model, the user then<br />
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