Testing and Monitoring for the Control of Strengthening Interventions of Santa Maria Gloriosa Dei Frari in Venice

The Basilica of Santa Maria Gloriosa dei Frari was involved by dangerous horizontal and vertical movements of the bell-tower which induced severe cracks on the supporting structures of the Basilica. After the installation of provisional reinforcing systems, two main works were carried out in order to decrease the movements of the bell-tower and the openings of the cracks in the structures of the Basilica. At first, the consolidation of the soil foundation of the bell-tower was carried out by using the soil-fracturing technique; then a structural joint was created between the bell-tower and the adjacent structures of the Basilica. All the phases of the interventions, which were completed in December 2008, were carefully checked by using an automatic monitoring system able to give in real time precious information on the movements of the structures. This monitoring system, which includes a direct pendulum, several crack-gauges and livellometric measures, is still active and it will continue to operate in the future for a log-term control of the behaviour of the Basilica after the consolidation works. This type of monitoring is able to guarantee the safety of the structure during the works and can be considered as a design tool which allows, through the application of the observational method, to change during the works the design of the strengthening interventions taking into account the real behaviour of the structure.