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At about 8.00 am of 20th December 2015, a fire started in a shop in Plasco building, located in center of Tehran, which at the end resulted in catastrophic collapse of the building and claimed the lives of 22 fire fighters and other people. According to the findings of the investigations, the main reason of ignition was non-permitted extension of cablings in the shop of the scene; for use of electrical heating devices. Plasco building was constructed before compiling of national building codes of Iran; hence fire safety rules were not properly implemented in the design of the building. This incident took the attention of Iranian society, Engineers and authorities to the need of the improvement of safety of the old buildings, which have been constructed before the establishment of national building code. In the other hand, the national building codes of Iran consists only the requirements for the new buildings and approximately no regulation has been pointed there for existing buildings. The incident was an alarm to the general public and accounted organizations that there might be many other buildings like Plasco in the large cities, which are threatening the safety of the users and the city. Therefore a national committee was appointed to investigate the different aspects of the incident and offers the solutions and measures which should be taken to prevent the similar experiences in the future. One of the subcommittees was accounted to fire engineering studies. The fire safety problems of the building were investigated. Some important shortages were as follows: high fire load in the building, especially because of high content of flammable textiles and clothes, open stairways without a protected shaft, open connection between false ceilings of all shops and corridors in the stories, lack of fire resistant shafts of mechanical installations between floors, lack of fire protection of steel structure, lack of any fire detection and automatic sprinkler in the building. The existing hose-reels didn’t have a regular maintenance and hence they could not be properly used by fire fighting forces. The Plasco was collapsed after about three and half hours of the ignition. Therefore the question was arisen how was the scenario of the fire growth and temperature rise in the building. Different tests were carried out on the sample materials taken from the debris of the building. Heat release rate (HRR) of the sample textiles was measured with cone calorimeter. The place of the building and depot of debris was visited by different special teams. Steel, concrete and other materials, which some of them were molten due to high temperature, was taken for further experimental works. Physical, mechanical, XRD/XRF, petrography and other tests have been carried out, from them only heat release test is discussing in this paper. The results showed high amount of HRR of the burned textile specimen. There were more than 580 mercantile units in Plasco, which most of them were clothing shops or related works. This high content of the textiles and clothing created a high fuel load in the building. Considering the design weaknesses of the building which were pointed out in the above, the fire could rapidly grow in all stories through open connected spaces. A fire modeling was carried out using FDS software and showed how the flames could be raised through windows, shafts and stairways to upper floors. The temperature rise was also investigated by the model. The results showed that the temperature rise, especially in floors 10 and 11 was suit for collapse of structural elements which was widely discussed in report of structure committee. The results also showed that the means of egress was not useable by occupants after only short minutes from the ignition, because of fire and smoke growth in the path.

Keywords: Plasco building, fire modeling, building regulation, cone calorimeter, heat release rate

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