Performance Based Fire Engineering Study of Subway Train Depot

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Problem Statement

A single-storey train depot is used for general maintenance and storage of commuter trains. As the building floor area exceeds 5000m2, the building must be installed with an engineered smoke control system ( Singapore Fire Code clause 7.5.1).


In order to conform to the prescriptive fire code, the smoke reservoir size cannot exceed 2000m2 and each reservoir must be served by adequate smoke venting louvers. Due to operational requirements (overhead crane system), it was not possible to provide smoke barriers to limit reservoir size to less than 2000m2. Therefore, all stakeholders agreed to use a Performance Based Design approach.


The root objective of a performance based design approach is to ensure tenable conditions for evacuation. The performance criteria is Available Safe Egress Time (ASET) > Required Safe Egress Time (RSET), i.e. visibility > 10m and temperature < 100oC at 2.5m above highest occupied level during evacuation. Computational Fluid Dynamics (CFD) fire simulations and evacuation studies were used to determine ASET and RSET respectively.


CFD was used to simulate a train fire for 20mins. The results show that (at 20mins), visibility > 10m and temperature < 100oC at 2.5m above highest occupied level (i.e. ASET ≥ 20mins). The predicted total evacuation timing for the depot was 8mins (i.e. RSET = 8mins). Since ASET > 2 x RSET, it is clear that the proposed Performance Based Design ensures Life Safety of the occupants.

Fig 1: Computational Domain of the Train Depot


Fig. 2: Temperature Contour at sections through Fire Source


Fig. 3: Velocity Contour at sections through Fire Source