A Post-Earthquake Fire Spread Model considering Damage of Building Components due to Seismic Motion and Heating of Fire

Abstract

A physics-based model for post-earthquake fire spread was developed by modifying the prototype model previously proposed by the authors. In the model, fire spread within urban area is simulated by predicting behavior of individual building fire under the thermal influence of other building fires. Target urban area consists of buildings with diverse level of damage due to seismic motion. The damage may even be progressed by heating of fire following earthquake. Damage of building members affects behavior of building fire as well as the criteria for building-to-building ignition. Indices representing the damage of building are as follow: bearing capacity of column; deficit ratio of walls and windows; and falling ratio of exterior material. Bearing capacity of a representative column is used as criteria for determining the collapse of entire building. Deficit on walls and windows may intensify combustion in fire involved room by letting fresh air supply from adjacent rooms. At the same time, this may cause room-to-room fire spread since it drastically augments the rate of heat transfer by radiation. Falling of exterior material let unprotected combustible exposed to external heating that increases probability of ignition. For the model validation, fire spread simulation in Kobe city at the time of 1995 Hyogo-ken Nanbu Earthquake was carried out. Reasonable agreement was obtained between observed and simulated behavior of fire spread.