Seismic assessment of historical masonry towers by means of simplified approaches and standard FEM

The seismic vulnerability assessment of eight historical masonry towers, located in the North-East region of Italy, is carried out by means of simplified approaches. Three-dimensional finite element models of the eight towers are created on the basis of geometrical data deduced from both existing available documentation and insitu surveys. First, preliminary eigen-frequency analyses are performed in order to obtain some basic information about the structural behavior of the different towers. Then, a simplified approach based on non-linear static pushover analyses is adopted for the seismic verification of the global performance of the eight towers. In order to avoid unnecessary complications due to the utilization of orthotropic damaging models requiring many material parameters, a damage plasticity approach is used for masonry. The essential aspects of the masonry material are reproduced with sufficient care, namely the very low tensile strength, damage in tension and crack-crushing in compression. From an overall analysis of the results, it can be observed that almost all the towers are able to resist the seismic action corresponding to Sag = 0.1 g, whereas the majority are unsafe at least along one geometric direction for Sag = 0.2 g. Finally, this study presents the evaluation of the seismic safety Index by means of the simplified sectional approach suggested by Italian Guidelines on Cultural Heritage. The collapse accelerations for the towers under consideration are compared and it is found that the results obtained with the different approaches are in a good agreement with a slight conservative trend for the simplified procedure proposed by Italian Guidelines.