Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Technical trade-offs using fixed fire fighting systems
The increasing use of fixed fire-fighting system (FFFS) in tunnels has put focus on a topic that has a history of being controversial. An upcoming controversy is related to the question if it is possible to reduce the design fire for the ventilation system or reduce the protection of the tunnel construction when a FFFS is installed? Additional subject sometimes discussed is the potential increase in the distances between escape exits. All these subjects need careful discussion and thinking before they can be fully accepted. The advantages and disadvantages needs to be thoroughly debated and discussed. The paper gives an overview of the arguments and discussion about the physics related to introduction of trade-offs when installing FFFS in tunnels. A reliability analysis using risk assessment process should be undertaken before use of technical trade-offs. With that fulfilled, following technical trade-offs are proposed for FFFS in the design of safety systems: (1) Using 60 % o f the total HRR with FFFS as the convective HRR for design of the ventilation system appears to be a conservative value to apply. For the total HRR with FFFS, full scale test data could be used, or for a normal deluge water spray system operated at a water flow rate of approximately 10 mm/min, 50 % of the total HRR without FFFS could be considered as the design fire or the total HRR with FFFS. This means that for a normal deluge spray system at approximately 10 mm/min, a 100 MW free bum fire could be reduced to 50 MW (50 % of 100 MW) by the FFFS and 30 MW convective HRR (60 % of 50 MW) could be used for estimation of the critical velocity and other parameters related to the design, such as pressure loss due to fire and negative slope. (2) Using ISO curve as the design time-temperature curve for tunnels with FFFS would cover most cases. (3) Using one-dimensional FED analysis is the most effective way to design the distance between escape exits in tunnels with FFFS, despite that much research is still required in this filed.
Technical trade-offs using fixed fire fighting systems
The increasing use of fixed fire-fighting system (FFFS) in tunnels has put focus on a topic that has a history of being controversial. An upcoming controversy is related to the question if it is possible to reduce the design fire for the ventilation system or reduce the protection of the tunnel construction when a FFFS is installed? Additional subject sometimes discussed is the potential increase in the distances between escape exits. All these subjects need careful discussion and thinking before they can be fully accepted. The advantages and disadvantages needs to be thoroughly debated and discussed. The paper gives an overview of the arguments and discussion about the physics related to introduction of trade-offs when installing FFFS in tunnels. A reliability analysis using risk assessment process should be undertaken before use of technical trade-offs. With that fulfilled, following technical trade-offs are proposed for FFFS in the design of safety systems: (1) Using 60 % o f the total HRR with FFFS as the convective HRR for design of the ventilation system appears to be a conservative value to apply. For the total HRR with FFFS, full scale test data could be used, or for a normal deluge water spray system operated at a water flow rate of approximately 10 mm/min, 50 % of the total HRR without FFFS could be considered as the design fire or the total HRR with FFFS. This means that for a normal deluge spray system at approximately 10 mm/min, a 100 MW free bum fire could be reduced to 50 MW (50 % of 100 MW) by the FFFS and 30 MW convective HRR (60 % of 50 MW) could be used for estimation of the critical velocity and other parameters related to the design, such as pressure loss due to fire and negative slope. (2) Using ISO curve as the design time-temperature curve for tunnels with FFFS would cover most cases. (3) Using one-dimensional FED analysis is the most effective way to design the distance between escape exits in tunnels with FFFS, despite that much research is still required in this filed.
Technical trade-offs using fixed fire fighting systems
Ingason, H. (Autor:in) / Li, Y.Z. (Autor:in)
2014
8 Seiten, Bilder, 20 Quellen
Aufsatz (Konferenz)
Englisch
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