Überwachung einer Großbrücke mit einbetonierten faseroptischen Sensoren

Monitoring of a highway viaduct via embedded fiber optic sensors

The condition of bridges is currently mainly assessed by means of periodic manual visual inspections. Additional structural health monitoring is primarily used when the structure is approaching the end of its service life. The installation of sensors is mostly costly, and changes can only be measured from this point onwards. Furthermore, extensometers or strain gauges provide local measurements only. In a pilot project on a busy highway in Austria, a new technology for bridge monitoring, which promises a paradigm shift in this regard, was investigated. Various fiber optic cables were laid in the formwork and embedded in concrete. Using various devices, which utilize different physical effects, fiber optic strain and temperature measurements were carried out during construction and after opening to traffic under dynamic excitation and traffic conditions. Processes such as concrete hardening, the lowering of the supporting structure, the release of the piers, the post-tensioning or the passage of trucks could be tracked closely. Strains and crack widths are measured along the entire length of the cable, even in areas that are not accessible, and can therefore considerably support visual inspections in the future. In the research project valuable insights into the advantages and disadvantages of different devices and the hurdles that stand in the way of a widespread application of the technology were gained.