Prediction of human movement for improved life safety compliance
Different buildings have varying occupant loads and the exit capacities to suit the building purposes and configurations. Ideally, all buildings must be designed to allow people to manoeuvre freely at all times and evacuate rapidly with no congestion during an emergency fire situation.
Computer evacuation modelling can be used to optimise the flow of occupants in a complex building with high occupant loads to evaluate the effective movement time for all occupants to evacuate the building during a fire situation.
SHEVS fire engineers use evacuation modelling tools such as SIMULEX and PATHFINDER to test and validate building configurations in terms of the occupant movement time to achieve the Required Safe Escape Time (RSET).
RSET comprises of 3 components;
i. Detection Time, tdet
-The time taken for the automatic detection system to be activated.
ii. Pre-movement time, tpre
-The time taken for the occupants to receive and process the cues, signals and other alarms and decide to evacuate.
iii. Movement time, tmove
-The time for the occupants to evacuate the development vicinity.
For occupant evacuating from the room on fire, the movement time shall represent the duration of the exit fire door remain open for smoke spill during occupant evacuation.
RSET = tdet + tpre + tmove
For any occupant evacuation to be successful, the time available for safe evacuation before untenable conditions occur must be greater than the minimum time required for safe escape.
In other words, ASET / RSET > SAFETY FACTOR
ASET : Available Safe Escape Time
(Time from ignition to start of untenable conditions)
RSET : Required Safe Escape Time
(Time upon the ignition till complete evacuation of the occupants to a place of safety)
Conservatively, a minimum safety factor of 2 shall be adopted wherever possible.
Find out more >> SCDF Singapore Fire Safety Engineering Guidelines (SFEG 2015)
Some of the benefits and applications of computer evacuation modelling include:
Testing and Validation of Evacuation Plans
PATHFINDER evacuation modelling was conducted to evaluate the adequacy of exit provisions to cope with the occupant loads and building layout.
Timed evacuation modelling was used to evaluate crowd movement scenarios to determine the optimal paths for occupant evacuation from exit staircases to external
Identification of “bottle-neck” queuing scenarios
PATHFINDER simulation was used to identify the cause of any congestion for the evacuation of bed-ridden patients using bed lifts in lieu of exit staircases for an existing hospital.
Feasibility studies were carried out for 2 evacuation scenarios for bed-ridden patients;
It was concluded that with phased evacuation, the use of bed lifts can be more efficient than the use of exit staircases.
Validation of Existing Exit Provisions
St Joseph’s Church at Victoria Street is a heritage building undergoing major renovation.
PATHFINDER simulation was used to determine the occupant movement time using the existing exit provisions and re-designated evacuation paths.
Both Pathfinder & CFD modelling were carried out to assess the ASET/RSET of the fire safety designs to address the inadequate provision of smoke venting area and the deviation in the mode of activation for the smoke vents.
Prediction of Movement Time for Auditorium
PATHFINDER simulation was used to determine the movement time taken for the spectators in an auditorium to evacuate the upper seating tiers before localized smoke logging.
CFD modelling were performed in parallel to determine the optimized smoke extraction rate needed to maintain a clear smoke layer at the upper seating tiers. In other words, no localized smoke logging should occur before the spectators vacated the upper seating tiers.
Use of advanced simulation techniques and fire engineering strategies with Innovation.
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