D. Inaudi et al., LOW-COHERENCE DEFORMATION SENSORS FOR THE MONITORING OF CIVIL-ENGINEERING STRUCTURES, Sensors and actuators. A, Physical, 44(2), 1994, pp. 125-130
An optical-fiber deformation sensor with a resolution of 10 mu m and a
n operational range of 60 mm has been realized. The system is based on
low-coherence interferometry in standard single-mode telecommunicatio
n fibers. It allows the monitoring of large structures over several mo
nths without noticeable drift. No continuous measurement is needed and
the system is insensitive to variations of the fiber losses. This tec
hnique has been applied to the monitoring of a 20 m x 5 m x 0.5 m, 120
ton concrete slab over six months. It is possible to measure the shri
nkage of concrete and its elastic coefficient during prestraining, giv
ing reproducible results in good agreement with theoretical calculatio
ns and measurements performed on small concrete samples. This paper de
scribes the optical arrangement and the procedures used to install opt
ical fibers in concrete.