A Review of Building Evacuation Models - NIST Virtual Library

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