Fire Resistive Design for Preventing Upward Fire Spread

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Recently the fires in which super high-rise building collapsed occurred relatively frequently in overseas countries. The following three reasons can be thought to the question why fire led to the collapses of the buildings: failure of first-aid fire fighting, lack of capabilities of structural member of fire compartment for preventing spread of fire, and lack of fire-resistive performance of building or its structural member. If all these conditions are met, building collapses. The second reason mentioned above all is regarded as an important factor for promoting spread of fire. Especially, defectiveness of the interlayer compartment causes upward fire spread, makes fire fighting activities from the floor above difficult, and constitutes a primary factor to make the fire large-scale. In the case of super high-rise building, lack of capabilities for preventing upward fire spread on typical floor constitutes a decisive factor in making fire extensive, because such building normally consists of continuous typical floors on the same plane surface. To prevent the upward fire spread, it is important to use higher spandrel for exterior wall of building and to construct it without fault. The height of spandrel varies depending on the intended use of the building and the shape of openings, but the height of about 1.2 m to 2.0 m is needed. In Japan in many cases the height of spandrel of a super high-rise building is around 90 cm. Using the spandrel of this size, delay of upward fire spread can be expected to some degree, but not enough to complete prevention. In addition, to prevent collapse of a super high-rise building by upward fire spread, it is indispensable to equip the system for first-aid fire fighting and use the structural members resistant to heating of fire.