Cumulative monitoring of strain in concrete structures with polymer optical fibers

An alternative approach to spatial sampling of strain and displacement, other than point-wise and distributed, is here proposed to the aim of crack monitoring in civil structures. The addressed method exploits a low cost optical technique for the measurement of the cumulative deformation of a polymer optical fibre (POF), used as a sensing element and is suitable for both dynamic and static measurements. Main features of this approach are the limited cost, the large dynamic deformation range enabled by POF, the large area covered by a single sensor, ruggedness and easiness of handling. The feasibility of the approach is demonstrated in a real test site scenario, in which the sensing system is used for long-term monitoring of cracks originated inside a road tunnel impacted by a landslide. Some general considerations will be also drawn about the possible application of that sensing system to the monitoring of physical measurands of geo-technical interest, other than strain.