Evaluation of the seismic response of historical masonry bell towers located in South-East Lombardy, Italy

This study presents some FE results regarding the behavior under horizontal loads of two existing masonry towers located in South-East Lombardy, Italy. The towers, albeit unique for geometric and architectural features, show some affinities that justify a comparative analysis, as for instance the location and the similar masonry material. Their structural behavior under horizontal loads is therefore influenced by geometrical issues, such as slenderness, walls thickness, perforations, irregularities, presence of internal vaults, etc., which may be responsible for a peculiar output. The geometry of the towers is deduced from both existing available documentation and in-situ surveys. On the basis of such geometrical data, a detailed 3D realistic mesh is conceived, with a point by point characterization of each single geometric element. The FE models are analyzed under seismic loads acting along geometric axes of the plan section, with non-linear dynamic excitation assumptions. A damage-plasticity material model exhibiting softening in both tension and compression, already available in the commercial code Abaqus, is used for masonry. Non-linear dynamic analyses are performed along both the X and Y directions with a real accelerogram scaled to different peak ground accelerations. Some results presented in this paper show the high vulnerability of ancient masonry towers under horizontal loads.