Bridge surveillance with fiber optic sensors

As one of the most important transit countries in Europe, Germany is faced with the challenge to increase the capacity and performance of the traffic infrastructure. Bridges are crucial in this context. Due to their high average age, highly expensive bridge monitoring with short maintenance intervals is necessary to guarantee the traffic safety. An intelligent system for monitoring the status of bridges in real time is currently under development. In order to determine the most suited sensor system for this application, three different types of sensor systems are under investigation: The first consists fiber-optic sensors based on Fiber Bragg Gratings. This system can measure strain, acceleration as well as temperature. The second is also a fiber-optic system based on Rayleigh backscattering. It is a distributed system, which allows to measure strain and temperature all along the fiber. Finally, electrical measurements are taken from strain gauges, accelerometers and resistance thermometers as a reference to the optical sensor systems. The sensor data are merged and processed in a suitably programmed neural network in order to provide information about the status of the bridge in real time. The approach offers significant potential for savings, because the surveillance, maintenance and planning of bridges becomes more efficient compared to convenient methods.