<title>Bridge monitoring by fiber optic deformation sensors: design, emplacement, and results</title>

Abstract

In 1995, our laboratory fitted a highway bridge near Lausanne (Switzerland) with low- coherence fiber optic deformation sensors. The engineers, who had designed the steel-concrete composite bridge, were interested in the strain distribution inside the concrete slab and in the effects induced by the concrete shrinkage. More than 30 fiber optic deformation sensors, a few vibrating string deformation sensors, thermoelectric couples as well as resistive strain gages were installed in the concrete deck and on the steel girders of this bridge. Three phases of the bridge life were monitored: concreting and thermal shrinkage, load test with heavy trucks and long term deformations. This contribution presents the fiber optic sensor design, the installation technique and the preliminary results obtained on this bridge.