建築物の防火対策の地震被害と火災危険性
建築物の防火対策は、地震により被害が生じると、他の被害と連鎖して正常に機能しなくなるが、こうした視点から被害の状況を分析した事例は少ない。本報告では、建築物の防火対策の被害を、被害の連関の観点から整理・分析し、これらの被害が、在館者の避難安全性に与える影響を明らかにすることを目的としている。
兵庫県南部地震における建物内の防火対策の被害調査を行い、被害の連関に注目して、避難安全性および火災危険性の観点から、防火対策に関わる被害の進展シナリオを作成した。また、煙流動に影響を与える防火対策の成否をパラメータとしたイベントツリーを作成し、煙流動シミュレーションによるケーススタディを行なった。その結果、以下のことが明らかとなった。
- 配管や水槽の破損による漏水や自家発電の停止は、各種の防火対策の成否に大きな影響を与える。
- 防火対策の被害に連関して警報が作動し、防災センターで全館の被害の状況を確認できなくなる。
- 防火戸の開閉障害は、避難経路確保、煙伝播防止の観点からとらえると、常時閉鎖型と常時開放型防火戸で、各々相矛盾する危険性を内在している。
- 地震後の被害により、複数の防火対策が正常に作動しないと、出火後、早期に煙が全館に伝播し、在館者の避難が困難になる。
Seismic Damage to Fire Safety Measures and Fire Risk in a Building
It has been pointed out that seismic damage to fire safety measures in a building greatly affect the lives and safety of its occupants and the risk of fire. This kind of damage leads to functional damage of the building's fire protection. In this paper, we shall discuss the relation of seismic damage of fire safety measures to the risk of fire after an earthquake.To accomplish this goal, a survey of fire safety measures was carried out on 16 buildings which suffered damage from 1995 Hyogo-Ken Nambu earthquake.
From the survey results, functional damage on evacuation and fire protection were analyzed qualitatively. Relational damage scenarios were constructed from the view of space in a building and elapsed time after an earthquake. Based on the scenarios, case studies for smoke spread in case of a fire were carried out by smoke simulation for probable cases of damage. Conclusions are as follows.
- Damage to the water supply or the emergency electrical power system has a great influence on the ability of fire safety measures to function.
- Simultaneous activation of several alarms for fire safety measures makes it difficult for managers in the building control room to respond to the emergency, because they cannot get correct information about the present state of the building.
- As for seismic damage to the fire doors, their two functions are potentially inconsistent. Those functions being the restraint of fire spread, and the ensurance of escape routes.
- If a fire occurs in a building after an earthquake, failures of multiple fire safety measures cause the early spread of smoke to non-fire floors.