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.1 Schematization of the escape routes as a hydraulic
network, where the pipes are the corridors and stairways, the valves
are the doors and restrictions in general, and the tanks are the public
spaces.
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.2 Calculation of the density D in the main escape
routes of each deck. In the case of cabin rows facing a corridor,
it is assumed that the people in the cabins simultaneously move into
the corridor; the corridor density is therefore the number of cabin
occupants per corridor unit area calculated considering the clear
width. For public spaces, it is assumed that all persons simultaneously
begin the evacuation at the exit door (the specific flow to be used
in the calculations is the door’s maximum specific flow); the
number of evacuees using each door may be assumed proportional to
the door clear width.
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.3 Calculation of the initial specific flows Fs,
by linear interpolation from table 1.1, as a function of the densities.
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.4 Calculation of the flow Fc for corridors and
doors, in the direction of the correspondent assigned escape stairway.
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.5 Once a transition point is reached; formula
(1.7) is used to obtain the outlet calculated flow(s) Fc. In cases
where two or more routes leave the transition point, it is assumed
that the flow Fc of each route is proportional to its clear width.
The outlet specific flow(s), Fs, is obtained as the outlet calculated
flow(s) divided by the clear width(s); two possibilities exist:
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.1 Fs does not exceed the maximum value of table
1.2; the corresponding outlet speed (S) is then taken by linear interpolation
from table 1.3, as a function of the specific flow; or
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.2 Fs exceeds the maximum value of table 1.2 above;
in this case, a queue will form at the transition point, Fs is the
maximum of table 1.2 and the corresponding outlet speed (S) is taken
from table 1.3.
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.6 The above procedure is repeated for each deck,
resulting in a set of values of calculated flows Fc and speed S, each
entering the assigned escape stairway.
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.7 Calculation, from N (number of persons entering
a flight or corridor) and from the relevant Fc, of the flow time tF
of each stairway and corridor. The flow time tF
of each escape route is the longest among those corresponding
to each portion of the escape route.
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.8 Calculation of the travel time tdeck
from
the farthest point of each escape route to the stairway, is defined
as the ratio of length/speed. For the various portions of the escape
route, the travel times should be summed up if the portions are used
in series, otherwise the largest among them should be adopted. This
calculation should be performed for each deck; as the people are assumed
to move in parallel on each deck to the assigned stairway, the dominant
value tdeck
should be taken as the largest
among them. No tdeck
is calculated for public
spaces.
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.9 Calculation, for each stair flight, of its
travel time as the ratio of inclined stair flight length and speed.
For each deck, the total stair travel time, tstair
,
is the sum of the travel times of all stairs flights connecting the
deck with the assembly station.
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.10 Calculation of the travel time t assembly
from the end of the stairway (at the assembly station deck) to the
entrance of the assembly station.
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.11 The overall time to travel along an escape
route to the assigned assembly station is:
|
tI
|
= |
tF
+ tdeck
+ tstair
+ tassembly
(2.2.11)
|
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.12 The procedure should be repeated for both
the day and night cases. This will result in two values (one for each
case) of tI
for each main escape route leading
to the assigned assembly station.
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.13 Congestion points are identified as follows:
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.1 in those spaces where the initial density is
equal, or greater than, 3.5 persons/m2; and
-
.2 in those locations where the difference between
inlet and outlet calculated flows (FC
) is
in more than 1.5 persons per second.
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.14 Once the calculation is performed for all
the escape routes, the highest tI
should be
selected for calculating the travel time T using formula (1.8).