Structural Health Monitoring of a Concrete Viaduct by Distributed Fibre Optic Sensors

The condition of bridges is currently mainly assessed by visual inspections, with structural health monitoring techniques being limited to structures approaching the end of their service life. In a pilot project on a busy Austrian highway, a new technology for bridge monitoring was implemented, which promises a paradigm shift in bridge inspections. Fibre optic cables were placed in the formwork and embedded in concrete. With various interrogators, which utilise different physical effects, fibre optic strain and temperature measurements were carried out during construction, under dynamic excitation and during traffic conditions. Processes such as the hardening of concrete, the lowering of the falsework, the post-tensioning or the passage of trucks on the bridge could be monitored. Strains and crack widths were measured along the cable, including also areas that are not otherwise accessible. The article presents the insights gained into the advantages and disadvantages of different approaches, while highlighting the considerable potential of this technology to support bridge inspections in the future.