Multidisciplinary forensic investigation of buildings in fire : the case of the Plasco Tower

Abstract

The Plasco Tower, a 17-story building constructed in 1962, was the tallest building in Iran until its collapse in 2017. This high-rise building in Tehran collapsed due to a fire accident that started on the 10th floor and travelled both vertically and horizontally within the building. One of the biggest challenges faced by the researchers in carrying out the forensic study is the lack of structural and architectural information on the tower. Most of the information about the tower was obtained by studying the debris found after the collapse. Several researchers tried to analyse the tower to understand the reasons for the collapse, but faced limitations in terms of fire and structural modelling. One of the major difficulties in analysing tall structures against fires like the Plasco tower is the complexity involved in sequentially coupling multiple software. This thesis aims to reconstruct the fire history and develop plausible theories explaining the collapse mechanism behind the partial collapse in the initial stages and the final global collapse. The thesis uses two approaches to integrating CFD (using software FDS) with the heat transfer and thermo-mechanical analysis modules of the OpenSees software framework. The first approach for software integration uses a Python-based interface called OpenFire, which is entirely open-source. In contrast, the second approach uses the GiD+OpenSees interface to achieve integration, which is faster, more flexible and allows for more complex and comprehensive simulation models to be developed. The OpenFire software package was used for sequential CFD, heat transfer, and thermo-mechanical analysis of a single floor. However, for conducting the full-scale forensic study of the Plasco tower collapse, the GiD+OpenSees interface was used. A detailed assessment of the strengths and design flaws of the Plasco tower against fire conditions was conducted. The thesis explores the reasons for the global collapse of the tower based on the detailed, sequentially coupled analyses carried out.