During the 2009 L’Aquila earthquake, the tower of Santo Stefano di Sessanio, the town’s iconic symbol, collapsed to the ground. The tower was believed to have been rendered vulnerable to collapse because of 20th-century renovations to the tower’s observation platform, which replaced a wooden deck with one made of reinforced concrete, thus making the tower top-heavy. In the current study, a numerical analysis was used for investigating the collapse behavior of the tower. Doing an initial elastic model of the tower did not allow any realistic prediction of the anomalous seismic behavior showed by the tower; the reason why only a stump of structure actually survived the earthquake remained unexplained. The collapse of the Medici tower is then investigated using a full 3D Applied Element Method (“AEM”). AEM is a discrete crack approach method in which the structure behavior till its collapse is followed. Two models for the structure of the tower were considered in this study. In the first model, the walls were modeled as regular brick elements neglecting the random real shape of the stones of the tower, while in the second model the real random shape of the stones was considered. Fully nonlinear dynamic analysis is carried out including the hysteretic constitutive models of the stones and connecting mortar. Damage obtained from regular elements analysis was somehow overestimated compared to the real damage. On the other hand, the real mesh analysis showed better results closer to reality.

Hadhoud, H., Fassieh, K., Gregory, A., Helmy, H., Tagel-Din, H. (2016). Collapse Analysis of the Santo Stefano Tower, 16th World Congress on Earthquake Engineering (16WCEE). Key Words: Heritage Masonry Structure; 3-D Applied Element Model; Nonlinear Dynamic Analysis.