Simplified assessment of the seismic risk of r/c buildings

The evaluation of the existing r/c buildings are often based only on a seismic vulnerability assessment and usually the seismic-resistant capacity is evaluated correspondently to the attainment of the ultimate limit state of a single element. This can lead to an incorrect estimation of the actual risk of a building and can be misleading in taking a decision on the priorities of the constructions that have to be improved in their seismic capacity. The decision making process should be supported by a correct risk evaluation related to a seismic attack. A simplified procedure for the risk assessment of the consequences of a seismic attack on a r/c building is presented in the paper. It provides to take the seismic hazard from the probabilistic definition given by the national code and to evaluate the vulnerability of the structure according to a multi-scenario view. Three damage scenarios characterized by different extension of the structural collapses are considered for the risk evaluation. The expected consequences on the building and occupants, injured and casualties, are computed for each scenario. The calculation of the consequences is based on the evaluation of a damage indicator that takes into account the extension of collapses of structural and non-structural elements. A risk indicator expressed in terms of annual probability of expected losses is finally determined. Both the economic consequences and the consequences on the occupants can be computed. Applications of the procedure to a actual sample buildings are also reported and results are discussed.