Seismic fragility assessment of masonry building aggregates: A case study in the old city Centre of Seixal, Portugal

Aggregates made of old masonry structures represent a very common structural typology in many cities of the world. The structural units along the aggregates are characterized frequently by structural and geometrical heterogeneities. But urban growth led to the formation of many historic centres with similar structural typologies. The present study aims to assess the seismic fragility of masonry building aggregates using the old city centre of Seixal as a case study. The analysis involved the assessment of the most prevalent structural typology in the study area, considering the variability of a set of structural and geometrical parameters. The variation of such parameters has allowed the definition of 36 different structural configurations, whose seismic performance behaviours were studied employing non‐linear static analyses. Based on the analyses, the peak ground accelerations (PGAC) corresponding to the attainment of the life safety limit state were obtained and the fragility curves were plotted. Furthermore, the behaviour of the structural configurations, analysed as isolated structural units, is also compared with their aggregate structural performance. Significant differences in the vulnerability of the buildings when isolated or in the aggregate are obtained, demonstrating that the seismic interactions between adjacent buildings should not be neglected. It was further possible to observe that the variation of the considered parameters significantly affects the seismic response of the building, particularly when the characteristics of the internal slabs are changed.