بررسی شدت رهایش گرمای مصالح و مدل‌سازی حریق در ساختمان پلاسکو

حدود ساعت 8 صبح سی‌ام دی ماه 1395، ساختمان پلاسکو در تهران دچار حریق شد. علت شروع حریق اتصال برق گزارش شده است. دلایل گسترش حریق و چگونگی آن بررسی شد. ساختمان پلاسکو دارای نقاط ضعف زیادی از نظر ایمنی در برابر آتش بود که موارد زیر را باید عنوان نمود: بار حریق بالا به علت مقادیر زیاد پارچه، اشکالات طرح پلکان، ارتباط کامل بین فضاها از طریق سقف‌های کاذب و شفت تاسیسات، عدم محافظت سازه فولادی در برابر آتش، عدم وجود جداسازی مقاوم در برابر آتش، عدم وجود سیستم‌های کشف، اعلام و اطفای خودکار حریق، عدم تعمیر و نگهداری صحیح از سیستم‌های موجود. آزمایش آتش بر روی پارچه‌ها صورت گرفت و نشان داد بار حریق در ساختمان بسیار بالا بوده است. مدل‌سازی کامپیوتری بر روی چگونگی گسترش حریق در ساختمان پلاسکو صورت گرفت. نتایج مدل نشان داد که حریق توانسته از طریق پنجره‌ها، فضاهای کاذب، پلکان و شفت آسانسور به فضاهای مجاور و به طبقات بالا گسترش یابد. همچنین افزایش دما در مناطق مختلف ساختمان، به علت آتش‌سوزی، نشان داده شد. نتایج نشان داد که افزایش دما در ساختمان، بخصوص در طبقات 10 و 11 برای رسیدن سازه به دماهای بحرانی و شکست سازه مستعد بوده است. همچنین مدل حریق نشان داد که مسیر پلکان در همان دقایق ابتدایی، به علت آکنده شدن از دود و تیرگی و نیز افزایش دما، برای افراد معمولی (بدون تجهیزات خاص) غیر قابل استفاده شده است.

Heat release rate of materials and fire modelling of Plasco building’s incident

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 nonpermitted 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 hosereels didn rsquo;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.