Seismic vulnerability assessment and fragility analysis of pre-code masonry buildings in Portugal

Despite the fact that in recent years Portugal has not seen the occurrence of high-magnitude earthquakes, it remains threatened by these events due to its geographic location. Since the 1960s, reinforced concrete has been the most used material for new constructions, however the historic urban centers are dominated by old unreinforced masonry (URM) buildings which techniques and construction materials have evolved since the Great Lisbon earthquake that occurred in 1755 with a magnitude around 8.5. Given the presence of these buildings in areas of significant seismicity, a comprehensive research is needed to assess the seismic risk and define mitigation policies. This kind of studies are often supported by empirical methods and based on expert judgment due to the high variability of the building stock and lack of information. The main purpose of this work is: i) to provide analytical fragility curves, supported by nonlinear static analysis, for the entire population of old masonry buildings, built before the introduction of the first design code for building safety against earthquakes (RSSCS) in 1958; ii) define vulnerability curves to be used by the technical community for seismic risk assessment of pre code URM buildings. The characterization of the building stock geometry and material properties is based on the previous information collected, which was useful to define representative archetypes and typologies.