Collapse analysis of the Clock and Fortified towers of Finale Emilia, Italy, after the 2012 Emilia Romagna seismic sequence: Lesson learned and reconstruction hypotheses

In the present paper, different full 3D FE numerical models exhibiting increasing levels of complexity are presented, to have both an insight into the causes of collapse of the Finale Emilia Clock and Fortified Towers in occasion of the 2012 Emilia Romagna, Italy, seismic sequence and propose effective reconstruction strategies. Two hypothetical rehabilitation interventions implemented before the earthquake sequence (which could be utilized as reference for a future reconstruction), one made with lime mortar restoration and the other with cement mortar deep repointing with injection, are evaluated from a seismic point of view. The numerical assessment includes modal analyses, a simplified procedure provided by the Italian Code for the Built Heritage, non-linear static (pushover) and full non-linear dynamic analyses. In all cases, full 3D realistic FE models derived from detailed geometric virtual models of both towers are used. Within the non-linear static and dynamic analyses, a damage plasticity model with distinct damage parameters in tension and compression is adopted. From the numerical results, both the role played by the actual geometry and the insufficient resistance of the original masonry material are addressed, also in light of the actual failure mechanisms observed. By quantitatively comparing the efficiency of the two methodologies of rehabilitation considered, it is found that very little damage develops when lime mortar is used, whereas less effective results are obtained when injections with cement mortar are used.