On January 19, 2017, the 16‐story Plasco tower located in Tehran, the capital city of Iran, collapsed in several stages, due to a fire lasting 3.5 h. This paper presents the results of numerical investigations on how the structure behaved during that incident. In this regard, initially, a part of floor system including main truss girders, secondary truss beams, tie beams, and reinforced concrete slab is simulated to study its deformed shape and collapse modes. Then 2D and 3D models of the building are developed to evaluate the global behavior of the structure under fire. The results show that at elevated temperatures, deflection of the floor system, main trusses, and out‐of‐plane bending of the beam‐to‐column gusset plates become excessive, leading to partial collapse of floor, in the location of fire initiation. Also, 2D models show that thermal expansion and catenary action of heated truss induce large lateral displacement and bending moment in perimeter column that cause failure of this column at about 650°C. Finally, 3D models indicate that general collapse of the building is initiated by buckling of the external columns located in the southern perimeter of the building. This result is in good agreement with videos and photos showing actual collapse of the structure.

中文翻译：

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火灾导致16层Plasco建筑物倒塌的结构研究

2017年1月19日，由于持续3.5小时的大火，位于伊朗首都德黑兰的16层Plasco塔楼分多个阶段坍塌。本文介绍了有关该事件发生期间结构行为的数值研究结果。在这方面，首先，模拟地板系统的一部分，包括主桁架梁，次桁架梁，系梁和钢筋混凝土板，以研究其变形形状和塌陷模式。然后，开发建筑物的2D和3D模型，以评估建筑物着火时的整体性能。结果表明，在升高的温度下，楼板系统，主桁架的挠度以及梁到柱衬板的平面外弯曲会过度，导致着火位置的楼板部分塌陷。也，2D模型表明，受热桁架的热膨胀和悬链线作用会在周边柱中引起较大的侧向位移和弯矩，从而导致该柱在约650°C时失效。最后，3D模型表明，建筑物的总体倒塌是由位于建筑物南侧的外部柱的屈曲引起的。该结果与显示结构实际坍塌的视频和照片非常吻合。