Bridge bearings equipped with optical fiber sensor for measuring vertical load through the support

The durability of bridges and the ability to maintain their initial structural capacity are topics of growing interest. For a long time, inspection programs have been carried out to follow up a changing state of large structures. To help managers in their decisions, an advanced metrology was introduced in sensitive parts of bridges to assess their structural aptitude. In particular, an abnormal behavior of the structure often causes a load re-distribution on its bearings. If the reaction force is monitored at the bearings, the entire structure can be assessed and its main deficiencies eventually detected. A technology based on using optical fiber sensors was developed and a prototype tested. A system of three or five sensors is incorporated in an external metallic plate put under the bearing. The microbending technique is used and light attenuation is measured. The shape of the plate grooves, containing the fibers, is chosen so that the sensor range and offset can be adapted to the operating load. Bearing reaction real time measurements, introduced into an automatic or semi-automatic processing, provide the structure with a certain 'intelligence.' Theoretical and experimental results are presented.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.