In the last few years restoration works were carried out on the roof and these interventions were probably the cause of a visible crack running along the inferior side of the main vault. Other smaller cracks have started to appear at ¼ span on the topside of the vault.






Aim of monitoring:

The instrumentation was used to measure the daily and seasonal variations in the crack openings and the vault curvature. This was done in order to point out any irreversible behavior.






Main results:
 

The SOFO sensors were selected because of their reliability, precision, simple installation and the possibility of carrying out automatic measurements. Once installed, the sensors are placed at a height of more than 6 m, making direct access difficult. Measurements could be carried out from the sacristy without disrupting the normal use of the church. By using an optical switching unit, the 10 sensors automatically took measurements over a period of a few weeks every three months. Manual measurements were carried out between the automatic measurements sessions. The measurements conducted over 6 months pointed to a reversible behavior: crack openings were correlated to temperature variations. Figure 1 shows the sensor’s emplacement. Figure 2 shows the deformations measured on the bottom and top in one of the measurement sections as well as the temperature variations during the same 3 week period.