|Author:||Ku, Chung Yee|
|Title:||A study on fire hazard and smoke control in large railway interchange stations|
|Advisors:||Chow, W. K. (BSE)|
|Subject:||Hong Kong Polytechnic University -- Dissertations|
Local transit -- Fires and fire prevention
|Department:||Department of Building Services Engineering|
|Pages:||244 pages : color illustrations|
|Abstract:||In a busy city like Hong Kong, railway interchange stations are obliged to cope with the growing population and the expansion of the railway network. As of now, a number of new railway lines are, or will soon be, in operation. Within the integrated railway network, the design of the new railway stations with smoke control via a smoke management system is becoming more and more complicated. Likewise, a timeline analysis of the Available Safe Egress Time (ASET)/Required Safe Egress Time (RSET) and a fire hazard assessment based on the architectural design and smoke management system must consider the effects of different fire scenarios, fire loads, and occupancy factors. Complicated station designs and the integration of the railway stations with other transport facilities, including Public Transport Interchanges, can produce problems in the evacuation of passengers in the event of fire. Due to complicated station designs, the standard prescriptive code on fire safety cannot be directly applied to all stations. Clearly, the station configuration built nowadays is commonly very complicated in terms of the building size, building height, and method of construction. In order to justify that the railway station is safe for use, it is necessary to adopt the performance-based fire engineering approach to work out a solution. In the design and planning of the railway station, especially one with a Public Transport Interchange, a fire evacuation strategy has to be developed based on the consideration of a number of important factors. As a general rule and design requirement, passengers within the fire incident place should be able to leave the place before becoming unduly affected by the fire and smoke; passengers in an area remote from the fire should be given sufficient and clear information to enable them to react according to the instructions from the station staff or clear announcements broadcast in the station. The prescriptive building codes deal with the provisions for escape based on the lengths of escape routes, width and number of exits, the time for evacuation, and the evacuation path. By using the Fire Dynamics Simulator (FDS), a Computational Fluid Dynamics (CFD) software simulation model, and the data obtained from experimental results, the fire hazards in relation to the smoke control system in the large railway stations can be assessed, and the ASET can be determined. The railway stations with complicated architectural layouts and evacuation route arrangements can be justified by the performance-based fire engineering approach of analysis.|
A smoke management system is a method of controlling the smoke generated by fires in railway stations. The objective of the smoke control system is to keep the smoke at high levels, thus facilitating the fire-fighting process and passenger evacuation. In this study, the smoke layer height and the ASET will be estimated via FDS simulation. With sufficient data collected from the CFD simulation results and experimental results from the scale model of a tilted enclosed space, the CFD simulation results can be compared, and the ASET from the CFD model by FDS can be validated. A fire safety management plan based on the validated results can then be developed to accommodate the railway station design. In large railway interchange stations, the main concourse areas are often connected to horizontal passenger subways, slightly tilted passenger corridors, and even tunnels for trains due to a construction alignment. In order to study fire characteristics in large railway interchange stations, a scale fire model of an enclosed space similar to the configuration of a tunnel, with the ratio of 1:40 and angles of 0°, 2°, 4°, and 6° to the horizontal, is created and studied. The fire source is modelled by the use of containers in different sizes in the 1:40 scale model of an enclosed space. A 37-mm-diameter pool fire is created to represent the Heat Release Rate (HRR) of 5 MW from a bulk of burning luggage. It is conventional in Hong Kong and many countries worldwide to adopt the convective heat flow as the steady-state design fire for smoke control calculations. The experimental results indicate that the flame-bending angle increases while the flame height decreases with an increase in the inclination angle of the enclosed space, as additional force is acting along the longitudinal direction with the gravitational force. It is also observed that the flame colour is independent of the tilted angle. Flame colour remains yellow at different tilted angles due to the supply of oxygen maintaining the reaction of the emissions of small carbon-based particles. Different tilted angles produce fires with different characteristics involving the flame pattern, gas temperature, and flame height. Fire engineers should take these factors into consideration in the design of fire and smoke control systems in large railway interchange stations. The use of timeline analysis in the performance-based fire engineering approach should be reviewed by fire engineers with knowledge in fire dynamics. In terms of railway station designs, exit arrangements should be carefully reviewed with the aid of a predictive evacuation model. Further systematic studies on human behaviour including a proper interpretation of fire and evacuation predictive models with the RSET data supported by the field measurements of crowd movements are recommended.
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