A fire staring in a densely-built urban area easily spreads to adjacent buildings. In the case of large earthquakes in which multiple fires may break out simultaneously, the spread of such fires may overwhelm the ability of firefighters and damage large areas. In this study, fire spread simulations were carried out in order to investigate behavior of fire spread in Kyoto Higashiyama area, one of the representatives of densely-built urban areas in Japan. A physics-based model was used in which the following mechanisms of fire spread are considered: thermal radiation heat transfer from fire-involved buildings; elevation of ambient temperature by wind-blown fire plumes; and spotting ignition by firebrands. The risk of fire spread was also analyzed by the Monte Carlo method to evaluate the expected magnitude of loss. The effect of uncertainty of the location of fire origin and the weather conditions was investigated.
KEYWORDS: risk assessment, modeling, urban conflagrations, densely-built environment
NOMENCLATURE LISTING
A physics-based model for post-earthquake fire spread was developed by modifying the prototype model previously proposed by the authors. In the new model, seismic motion and heating of fire are both considered as the causes of damage upon building components. The damage affects burning behavior of a fire involved building as well as behavior of building-to-building fire spread. For validation of the new model, simulation of fire spread which followed 1995 Kobe earthquake was conducted. Behavior of fire spread obtained by the numerical simulation was compared with the observed data. Reasonable agreement was obtained with regard to the number of burnt buildings.KEYWORDS: post-earthquake fire, urban fire, fire spread, physics-based model, Kobe city.
NOMENCLATURE LISTING
The prototype model previously developed by the authors was improved in order to simulate the behavior of fire spread in an earthquake-affected urban area. In the new model, seismic motion and heating by fire are both considered as the causes of damage to building components. The damage affects the burning behavior of a fire-involved building, as well as the behavior of building-to-building fire spread. For validation of the new model, a simulation of the fire spread that followed 1995 Kobe earthquake was conducted. The behavior of the fire spread obtained by the numerical simulation was compared with the observed data. Reasonable agreement was obtained with regard to the number of burned buildings.
An experiment on fire fighting activity using portable fire pumps was carried out for 41 subject teams of variable characteristics. It was conducted according to an activity scenario for a team consists of three community residents. The scenario involves six sequential processes starting with detection of fire and ending up with discharge of water. Amount of time required for the operation of portable fire pump was measured for each of the process. The obtained distributions of the required times were approximated with lognormal curves providing expressions necessary for the evaluation of community-scale capability of fire prevention. It is also shown that the occurrence of erroneous operations was not that dependent on the training experience of the residents in the past. The rate of water thrown into a model fire room through a window was measured for 84 residents. It was found that the rates were almost proportional to the direct distance between the target window and the nozzle head.
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