Traditional vs innovative structural health monitoring of monumental structures: A case study

This work reports an experimental comparison between two measurement techniques of crack openings: a traditional method based on a mechanical device and the OTTO system based on fiber optic sensors and developed by CELM. The main characteristics of both methods are presented, with their main advantages, drawbacks, and peculiarities. The testing campaign conducted on a historical church erected in the first half of the eighteenth century is then described in detail. Cracks evaluation has a key role in the safety assessment of a monumental building and it is the base for a proper restoration design and intervention plan. The measurements monthly collected using the two described methods are compared and the performances of the two monitoring systems are discussed from both technical and economical points of view. Of particular interest are the unique characteristics of fiber Bragg gratings (FBG) sensors including their noninvasiveness and their extremely high precision in both displacement and time resolutions. These features make FBG sensors the ideal candidates for long term or not invasive monitoring. On the other hand, mechanical measurements remain the best candidates for initial or sporadic measurements. Copyright (C) 2010 John Wiley & Sons, Ltd.