Fire Structural Response of the Plasco Building: A Preliminary Investigation Report

The fire-induced collapse of the 16-story Plasco building in Tehran city in January 2017 caused many deaths and serious injuries. This paper investigates the structural response of the building during that fire to understand how the building became unstable. As documented, the fire initiated on the tenth floor, and then involved stories 11–14 through a vertically traveling fire. As the occupancy type of the building had changed over time, the analysis was performed based on an estimated fire load density of 1900 MJ/m2 on the day of the catastrophe. The results showed that the structure was able to resist the applied loads when the fire remained within stories 10 and 11. When the fire involved stories 10–14, however, the structure began to fail, starting with the failure of the ceiling trusses. The results also indicated that as the columns were protected by a layer of masonry, they were able to tolerate their applied loads. The analysis was also re-performed based on a fire load density of 511 MJ/m2, which is the fire load recommended by most fire codes for a similar occupancy type. The results showed that no structural failure would have occurred under that fire load. This study indicates that changing the occupancy type of a building without adopting proper mitigation strategies can be catastrophic.

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