Evaluation of the Effective Factors on Increasing the Risk of Damages to Urban Buildings in Post-earthquake Fire Crisis by AHP Method

Background and Objectives: Earthquake can be the source of many secondary disasters. Fire is one of the most important secondary hazards after the earthquake. In some cases, post-earthquake fires, in urban areas, may cause far more severe damages than the earthquake itself. After the earthquake, the risk of fire is greatly increased due to the existence of sources of fire, such as arteries of gas and electricity, with the possible presence of gas storage or distribution stations. On the other hand, the general conditions of the around urban environment may play a very important role in fire behavior. Method: In this study, by using descriptive-analytical research method, in order to determine the evaluation of post-disaster fire risk, among the various available methods in this field, the effective criteria and sub-criteria on the post-earthquake fire and vulnerability of urban areas were extracted. These criteria included four main criteria of access, structures, methods of confronting, and risk factors, so, each has sub-criteria. These sub-criteria were then prioritized by the expert group using paired comparison method. At the end, in order to study the impact of structural material on the vulnerability, the phenomenon of post-earthquake fire in the steel building is modeled and analyzed. Finding: The structural index increases the risk of post-earthquake fire in buildings. The extent of the fire does not have a significant effect on the structures that have fire-proof cover on their columns, and the type of damages depends on the characteristics and resistance of the beam to the fire. In non-fire-proof construction, the fire scenario will have a significant impact on the structure’s overall behavior. As the fire spreads, the whole function of construction will be disrupted and will not withstand the loads. Conclusion: The results of the study showed that in order to assess the risk of fire caused by earthquake, structural criteria, number of urban main gas valves and structural height have the most significant role to be considered. In the case of failure or not considering any of the above criteria, the accident may extend and fatalities and loses will increase. It is also recommended to use fire-proof covers on the pillars to reinforce existing buildings after the earthquake due to economic and technical constraints.