Singapore Fire Safety Engineering Guidelines 2015_1.pdf

Horizontal travel speed will be calculated using

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Horizontal travel speed will be calculated using equation (4.2). S = k akD - - - - - - - - - - (4.2) Where S is horizontal travel speed (m/s) k is 1.4 for horizontal travel a is 0.266 D is the occupant density of the affected space (persons/m 2 ) Horizontal travel
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35 Horizontal travel time is then calculated using equation (4.3) below: t trav = L trav / S - - - - - - - - - - (4.3) Where L trav is the required travel distance (m) (ii) For vertical travel, the values used for the factor k are a function of the stair riser and thread as shown in Table 4.2. Vertical travel Table 4.1: Constants relating to horizontal and stair travel (extracted from PD- 7974 Part 6) Exit route element k Speed Corridor, aisle, ramp, doorway 1.40 1.19 Riser (mm) Tread (mm) 191 254 1.00 0.85 178 279 1.08 0.95 165 305 1.16 1.00 165 330 1.23 1.05 (iii) Table 4.3 and 4.4 also lists some typical travel speeds for occupants of different levels of mobility, both for horizontal travel as well as vertical travel via staircase. Different levels of mobility.
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36 Table 4.2: Typical horizontal travel speeds for occupants of different mobility levels Table 4.3: Typical travel speeds along staircase for occupants of different mobility levels
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37 (b) Flow time (t flow ) Flow time (i) The flow rate of persons passing through a particular point along an exit route can be calculated using equation (4.4): F c = (1-aD)kDW e - - - - - - - - - - (4.4) Where: F c is the calculated flow rate (persons/s) D is the occupant density near flow constriction (persons/m 2 ) W e is the effective width of component being traversed (m) k and a are defined in equation (4.2) above. Flow rates (ii) The effective width for various exit route elements can be determined from Table 4.4, by subtracting the boundary layer on each side from the measured exit width. For doorways that are not mechanically held open, a maximum flow rate of 50 persons/min/door leaf is recommended for design. Effective width Table 4.4: Boundary layer width used to determine effective width SFPE Handbook of Fire Protection Engineering, edition 3 (Table 3.14.1)
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38 (iii) For flows through a doorway, the occupant density to be used in equation ( 4.5) can be estimated to be 1.9 persons/m 2 . This value can be referred from the New Zealand Document C/VM2 [2] document. Flow through doorway The flow time can then be determined from the flow rate using equation (4.5): t flow = Number of occupants / F c - - - - - - - - (4.5) 4.5 Evacuation Models Evacuation modelling is increasingly becoming a part of performance-based analyses to assess the level of life safety provided in buildings. In some cases, FSEs use hand calculations to assess life safety, and in others, evacuation models are used. Hand calculations may be allowed for occupancies with a lower occupant loading, such as factories and warehouses. However, for buildings/spaces with large occupant loads such as in shopping centres, exhibition halls, offices and places of public resort and the like, evacuation modelling would be required by SCDF. If unsure, FSE is encouraged to consult SCDF before finalising the FEDB.
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