Seismic risk of traditional unreinforced masonry buildings of Barcelona, Spain

The unreinforced masonry residential buildings of Barcelona have a high seismic vulnerability not only due to their average age of more than 80 years but also because they were designed and built without any consideration of the seismic action. At the same time, their typology has particular features, typical of the customary constructive techniques of the city, which increase even more the vulnerability. The city is located in an area of low-to-moderate seismic hazard but the high degree of vulnerability of the buildings leads to a significant risk even in the case of not excessively severe earthquakes. Typical unreinforced masonry buildings (URM) of Barcelona have six and even seven storeys with a total height of 22m to 24.4m, respectively. To analyze the dynamic behaviour of the buildings, the TreMuri computer program was used, which is an excellent tool to describe the non-linear in-plane mechanical behaviour of masonry panels and to assess the expected damage of masonry buildings due to earthquakes. A pushover analysis was carried out, by applying a lateral loading pattern corresponding to the mode of vibration of the structures characterizing their lateral, translational, behaviour (third mode). In this way, the capacity curves of the buildings have been obtained and then, by using the demand spectra, the performance points have been determined. Considering a lognormal probability distribution, seismic fragility curves have been finally obtained, allowing evaluating the failure probability of the building.