ANALYSIS OF DAMAGE AND DIAGNOSTIC INVESTIGATIONS ON TRICARICO CATHEDRAL (ITALY)

Tricarico Cathedral, dating back to 11th century, nowadays presents widespread damage. The elements which are most damaged and at risk of collapse are the piers of the nave. They consist of a square core surrounded by pilaster strips. Integrated diagnostic investigations have been carried out in order to characterize the structural instability phenomenon which causes the damage, thus providing information useful for restoration interventions. In particular, endoscopic investigations permitted to ascertain the lack of connection between the pilaster strips and the core. The stone has good properties, as verified through ultrasonic tests. Sonic tests and GPR investigations highlighted that the cores of a number of piers present velocities and reflections, respectively, which can be referred to fractures or voids. Moreover, GPR investigations highlighted reflections in the pilaster strips which are typical of a severe and widespread decay, in agreement with visual inspection. Porosity measures were carried out on core samples apparently undamaged, and on an individual sample macroscopically damaged. Measures of ambient vibrations provided the fundamental frequency of structures by the HVSR technique (Horizontal to Vertical Spectral Ratio). The measures were carried out on the soil, the facade, the left aisle and the bell tower. The HVSR is interpreted comparing measures carried out in adjacent structures also with the aim to detect coupling phenomena (double resonance) between the eigenfrequencies of the structural macroelements and the soil.