Settlement induced damage modelling of historical buildings: the bell tower of the 'Basilica dei Frari' in Venice

The paper presents the case study of the “Basilica dei Frari” in Venice for which a non linear numerical analysis has been recently performed in order to assess its structural conditions. In fact, from the end of its construction, in the XIV century, the building suffered from structural deteriorations mainly due to settlements affecting the bell-tower. A main structural intervention was carried out at the beginning of the XX century, aimed at stopping the outward tilting process of the tower. The intervention was so effective that it induced an opposite effect on the tower, which started to rotate towards the cathedral. Several studies were carried out since then to evaluate the interaction between tower and church, including in recent years structural monitoring and numerical modelling, besides a strengthening intervention consisting in soil micro-fracturing. A non linear numerical model of the church-tower complex was implemented and compared to the outcomes of the available experimental data (monitoring, investigations), also considering the historical process leading to the present day conditions. To gain reliable settlement damage predictions it was necessary to adopt tensile-softening crack models in the numerical studies and perform non linear analyses able to trace the complete response of the structure. The aim of the modeling was also, besides the assessment of the structural conditions of the complex, to predict the structural effects of the physical “separation” between tower and cathedral.