Seismic assessment of a venetian bell tower taking into account soil-structure interaction

The paper gives a preliminary insight into the seismic vulnerability of bell towers, discussing a real case study, namely a masonry tower built in XIX century and located in the Province of Venice (Italy). Such a case study is fully investigated using different advanced FE strategies. The case study shows structural features often common in other cases, such as the foundation rotation due to soft soils, which causes the tower to lean. Both these parameters, the soil-structure interaction and the inclination, are expected to play a crucial role in the dynamic response and the lateral bearing capacity reduction. The present literature suggests different approaches to model and to account for such parameters, whereas technical codes mostly seem to propose simplified procedures that result in an underestimation of the real effect. The role of the soil is observed to be crucial in the shape and excited mass changes of the natural modes, thus implicitly modifying the seismic response. Furthermore, in general, the out-of-verticality of a tower causes the concentration of the vertical stresses and a significant capacity drop. In the present paper, different FE simulations are performed in order to investigate the actual dynamic behavior of the tower under study, to be compared with standard modeling used for bell towers.