Non-destructive techniques and monitoring for the evolutive damage detection of an ancient masonry structure

In the present article non-destructive testing evaluation of the existing damage evolution has been applied to some buildings of the medieval town of Craco (Matera, Italy) and, in particular, to the Normand tower. Actually the little town of Craco is totally abandoned as a consequence of the activation of the landslide motions of its soil depth. Nevertheless, the Normand tower still stands because it is located on a stable and stiffer foundation ground. The tower was built in the XII century. It is 20 m tall and has a symmetric square plan, with dimensions 11 m x 11 m; it was built for defense against enemy attacks. Inside the tower a cistern in reinforced concrete was placed in 1949. It is not connected to the structural walls of the tower; however it represents an obstacle for installing the damage detection equipment and sensors. In this article a preliminary study on the masonry structure of the Normand tower is carried on. A finite element numerical model has been developed and a modal analysis has been performed. The final aim of the research is to find out the evolutionary stage of the cracks and to propose a possible retrofit of the tower.