Collapse Risk Assessment of Urban Areas due to Earthquake

The capital of Iran، Tehran، has a major role in the political، economic، cultural and services at the regional، national and international scale. Occurrence of any disaster in the capital could cause tremendous consequences، especially on national security، politic، and economy of the country. In this article، the collapse of the buildings due to earthquakes is investigated. Generally، collapsing the buildings will lead to the largest physical damage as well as human loss during an earthquake. Investigating the collapse of buildings at one of the regions in Tehran after the earthquake not only makes a clear view of that region future after disaster، but also it helps urban managers prioritize different retrofitting measures. In this regard، uncertainties influencing the risk assessment of the collapse is originated from the type of structures، height of buildings، applied seismic design codes، and type of soil are considered in the study using logic tree method. Fragility curve is a factor for determining the percentage chance of stating the damage and consequently، the collapse. Developing fragility curves based on region’s conditions is a necessary task to justify the results of the study. In this paper، after introducing the local means of developing fragility curves، the studied region is divided into smaller cells based on soil characteristics and then the collapse risk of different buildings in each cell is studied separately based on a proposed algorithm. At the end، considering seismic analysis and collapse probability for existing buildings the most critical types of buildings would be determined based on the results of average and maximum collapse possibility. Furthermore، the results of collapse assessment are presented for two scenarios in order to evaluate retrofitting by enhancing of seismic design code.