Seismic vulnerability of leaning masonry towers located in Emilia-Romagna region, Italy: FE analyses of four case studies

Four inclined masonry towers are investigated in this paper in order to study the behavior under horizontal loads and the role of inclination on the seismic vulnerability. The towers are located in the North-East of Italy, a moderate seismicity region that was recently stricken by an earthquake with two major seismic events of magnitude 5.8 and 5.9. These towers date back to four to nine centuries ago and are well representative of the towers of the region. They present a meaningful inclination cumulated over years, which has a significant influence on the bearing capacity under lateral loads. Some retrofitting interventions were recently carried out by introducing tendons and hooping systems in order to ensure a box behavior and preclude the spreading of dangerous cracks due to the insufficient tensile strength of the masonry material. The structural behavior of the towers under horizontal loads is influenced by some geometrical issues, such as slenderness, walls thickness, perforations, irregularities, but the main aim of the paper is to provide an insight on the role played by inclination. The case studies are chosen to exhibit different values of slenderness in order to include a large range of geometrical cases for the assessment of the seismic vulnerability of the towers. Numerical analyses are carried out considering the effects of the retrofitting interventions too. As expected, pushover analyses show that inclination may increase the seismic vulnerability of the masonry towers comparing the results obtained for the inclined real case and the hypothetical vertical case.