Possible Improvements to Current Design Practices in Fire Safety Design for Road Tunnels

摘要

The fi re safety design for road tunnels includes the following aspects: active systems, passivernprovisions and operational procedures. The active systems include the smoke control system, fi rernsuppression system, detection system and fi re fi ghter’s assistance systems. Passive provisions includernescape passages, fi re separation and fi re resistance systems. The operational procedures refer to fi rernfi ghter access, reporting and alerts, evacuation processes and crowd control.rnCurrently, these systems are typically designed by different designers or teams. These systems arernintended to work together in a coordinated manner to provide the desired safety outcome. However,rnin practice, this is not always happening. The fi re engineering process is supposed to bring togetherrnall these aspects and arrive at an integrated safety system. The fi re engineering process in practicernis not integrating the design with the practice or reality and is thus arriving at less than desirablyrneffi cient safety systems.rnThe example of design inputs shows how disconnected each system design basis is. The smokerncontrol system design is based on the design fi re size. The performance of the smoke control systemrnis to achieve a smoke free environment for a defi ned space for a particular fi re size – the design fi re.rnThe fi re suppression system – most commonly sprinklers or deluge systems, is designed accordingrnto codes and to achieve a certain water discharge rate. The fi re detection system is designed torndetect temperature rise/rate of rise and perhaps density of smoke. Fire separation is determined tornprovide a certain period of service – mostly for structural elements. Escape route size and locationrnis determined mostly by code compliance. Evacuation procedures are determined by Authorityrnoperational requirements rather than human behaviour.rnTo arrive at an integrated fi re safety system, the design basis and performances must be coordinated.rnAn approach using fi re scenarios would ensure all systems are designed to a common performancernrequirement. This paper will discuss how the current design approach outcomes compared with a fi rernscenario approach. More effective and effi cient fi re safety systems would require the stake holders tornunderstand the implication of this approach and to embrace this through the fi re engineering process.