Collapse of the clock tower in Finale Emilia after the May 2012 Emilia Romagna earthquake sequence: Numerical insight

The paper presents the final results of a wide numerical campaign conducted by the authors at the Technical University of Milan in cooperation with the Italian Cultural and Architectural Heritage Ministry (MiBAC) on the clock tower in Finale Emilia (Italy), collapsed during the main shock of the devastating May 20-29, 2012 seismic sequence. The analyses are aimed at better understanding the causes at the base of the collapse of the tower. The two main seismic events, occurred on May 20 and 29, were characterized by the presence of low frequency ground motions, with relevant vertical components. Consequently, structures having natural periods greater than those typical of ordinary buildings - such as the one analyzed - have been severely damaged. After the first tremor (on the 20th of May), the clock-tower was split in two, with one half collapsing into rubble and the other standing precariously. The subsequent strong aftershock caused the almost total failure of the structure.To investigate the behavior of the tower under seismic loads, a number of numerical analyses are performed, including simplified static analyses according to Italian Guidelines on architectural heritage, spectral response, non-linear static (pushover and kinematic limit analysis) and full non-linear dynamic analyses. In all cases, a full 3D detailed FE model is adopted. When dealing with the FEM non-linear dynamic analysis, a smeared crack isotropic damage model already implemented in ABAQUS is adopted.From the numerical results, both the role played by the actual geometry and the insufficient resistance of the constituent materials are envisaged, also in light of the actual failure mechanism. In all cases, the numerical analyses provide a valuable picture of all possible failure mechanisms, thus giving useful hints for the reconstruction of the tower.