The recent decade has seen aging bridge infrastructure, especially in developed countries, at an unprecedented rate. Their scheduled maintenance and detection of gradual damages are challenging with decreasing number of skilled engineers. To solve these problems, we aim to investigate the possibility of bridge monitoring by distributed acoustic sensing (DAS) system, which uses optical fiber cables to sense surrounding vibrations. Most conventional monitoring methods, such as accelerometer-based point sensors, require a dedicated location for installation on bridges. However, DAS can obtain bridge vibration responses through Rayleigh backscattered light from optical fibers already laid for communication purposes without attaching to a dedicated location for bridge monitoring. The multiple measurement positions of one bridge are possible by taking advantage of optical fiber as a line sensor, hence expanding the monitoring of multiple bridges simultaneously over the road infrastructure. This study also discusses the statistical characteristics of bridge vibration responses measured by the DAS system. We experimented on a model bridge to evaluate the sensing performance and detection capability of the damaged condition, where the damaged condition represents the three saw cuts on both sides of the web plates of the model bridge. The experiment results evaluated from analysis of variance using the F-test show that frequency responses of DAS in both intact and damaged bridge conditions matched those of accelerometers used as a reference in this study. Our results suggest that DAS can be applicable to bridge damage detection like accelerometers.
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