A probabilistic model to compute seismic risk of buildings. Application to urban areas

Abstract

One of the main objectives of the seismic risk management is the creation of methodologies to take decisions about the seismic risk of buildings. In order to take these decisions it is necessary to have estimations about the seismic risk of each building or group of buildings studied. In the present work a probabilistic model to compute seismic risk in buildings is developed. According to this model, the seismic risk of buildings can be estimated considering three main elements: 1) The seismic vulnerability of the buildings; 2) The seismic hazard in the place where the buildings are located; and 3) The seismic response of the buildings. It is known that each one of these three elements has important uncertainties related. For this reason, a probabilistic point of view is considered in the approach proposed to estimate seismic risk. In order to highlight this probabilistic approach, a new method to compute seismic risk in urban areas is developed. It has as starting point the LM1 RISK-UE method and it is called herein mLM1 method. Curves of physical damage states versus annual frequency of occurrence are used in this method to express the seismic risk. The main steps of the mLM1 method are: 1) Probabilistic seismic vulnerability analysis; 2) Probabilistic seismic hazard analysis; 3) Probabilistic estimation of the seismic risk. In order to highlight the application of this new method the seismic risk of 8657 buildings that are located in the Eixample district of Barcelona was estimated. Seismic risk curves were obtained for each one of the studied buildings in the Eixample district. Additionally, average seismic risk curves were obtained in order to express the risk for the whole district. According to these seismic risk curves, the annual frequency of occurrence of the moderate damage grade in the Eixample district is a value between 0.00117 and 0.00297, with a mean value of 0.00209. This also means that the moderate damage grade in the Eixample district will occur in average one time every R years; where R is a value between 337 and 857 years, with a mean value of 478 years.