Bridge monitoring using a 64-channel fiber bragg grating system

Fiber Bragg grating (FBG) optical sensor systems have been shown to provide excellent multi-point measurements of strain in spatially extended structures such as bridges. Their ability to be multiplexed easily allows effective population of the structure such that spatio-temporal measurements can be obtained. In this paper, the application of a 64-channel FBG system to monitor the dynamic strain response of an in-service interstate bridge, is reported. FBG sensors were attached to seven different supporting girders at various locations along one span of the bridge. With an interrogation speed of 45 Hz after averaging, the sensors were monitored under a variety of traffic conditions, including ambient conditions and single-vehicle loading with known weight and speed. Selected results from the field test reported here indicate that an optical FBG sensor system is well-suited for obtaining data for a number of bridge-related applications, including bending shape reconstruction, transient traffic loadings, weigh-in-motion, possible vehicle identification, vehicle speed, and other dynamic characteristics of the structure.