SEISMIC COLLAPSE RISK ASSESSMENT OF MID-RISE CONCRETE BUILDINGS IN TEHRAN MEGACITY

Abstract eng:
Iran is one of the most seismically active regions in the world. A major challenge of identifying all high-risk buildings should be embarked in large cities of Iran such as Tehran. Obviously, collapse is the most important performance level of seismic risk assessment of these buildings. This paper focuses on developing a new methodology on the basis of modern seismic guidelines (FEMA-P695 and ATC-78-1) for seismic collapse risk assessment of the existing mid - rise reinforced concrete buildings in Tehran. A new methodology is introduced briefly. Then, it has been implemented for two types of midrise buildings having 7 and 10 stories buildings they are all engineered buildings constructed in Tehran during past 25 years. Two archetypes which made up of ensembles of them were selected for demonstrating the proposed methodology. The archetype buildings are selected in a way that flexural failure mode under seismic loads would be dominant for them. Several nonlinear analyses were performed to evaluate structural responses of this archetype model under moderate and severe earthquakes. All nonlinear analytical models were implemented in the OpenSees (2016) structural analysis software. A simulation model for components and structural system capable of capturing flexural collapse modes are applied. Meanwhile, a lumped plasticity model, developed by Ibarra et al. (2003), is used to detect severe deterioration that precipitates sideway collapse. A number of parameters, as calibrated in FEMAP695, are used in this model. A collapse drift matrix is developed for each archetype to distinguish between the partial collapse of each story and the conventional collapse detection through IDA curves. The collapse drift matrix affects the collapse capacity of the reinforced concrete buildings strongly. Under the framework of this new methodology, an attempt is made to achieve reliable results for the studied archetype structures. Also, the existing limitations and uncertainties of this proposed methodology are summarized and discussed. 1

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