Strtain measure in laboratory experiments on concrete beams by means of optical fiber sensors

In this paper, experimental measurements along concrete beams, by the use of a portable "Brillouin optical time domain analysis sensor" (BOTDA) are reported. A singlemode optical fiber was attached to the beam in order to detect both tensile and compressive strains. The sensor has been attached along the beam's length at different vertical positions, hence it is possible to measure the longitudinal strain at different heights with respect to the neutral axis of the flexural deformation. The moment-curvature relationship has been calculated from the measured strain and effectiveness of the device has been confirmed. Finally, examples of identification of cracks and failures of the beams is reported.