Vulnerabilidad sísmica de los edificios de hormigón armado con forjados reticulares

Seismic vulnerability of reinforced concrete buildings with waffled slabs

Vulnerability studies are very important to evaluate the seismic risk and its application is particularly interesting in urban areas located in low to moderate seismic hazard regions where the growth of the population and the absence of adequate seismic resistant prescriptions for buildings increase the seismic risk. Very often, in these areas, a large number of existing reinforced concrete (RC) frame structures have been designed mainly for gravity loads, for their lateral resistance has been determined without adequate seismic resistant considerations or according to old seismic codes, in which ductile detailing are not explicitly required. It is very likely that these buildings, when subjected to a maximum credible seismic event, suffer more damage than reasonable. Actually, many of the housings in Barcelona, Spain, are multi-storey waffle slabs reinforced concrete buildings. In fact, this typology is the second most representative in the city and the number of this type of buildings is increasing because, at present, this is the most extended construction system. This work is a contribution to the analysis of the seismic behaviour of these buildings and it faces the seismic risk analysis in an urban area situated in a low seismic hazard region. In order to carry out a suitable analysis it is necessary to have enormous information, that often it is not possible and, in addition, there exists a great amount of involved uncertainties; therefore, the adequate treatment of the problem is the probabilistic. In this work, we evaluate the vulnerability and the seismic risk of waffle slabs reinforced concrete buildings. The structural models used in the analysis correspond to buildings of 8, 5, 3 and 2 storeys. For each one of these buildings capacity and fragility curves are obtained. For the credible seismic demand in Barcelona, we consider two specific seismic scenarios. Taking into account all these results, the probability damage matrixes are obtained.