Preliminary Results on the Monitoring of an In-Service Bridge Using a 32-Channel Fiber Bragg Grating Sensor System

摘要

This report describes the preliminary results of the performance of a 32-channel fiber Bragg grating (FBG) system used to monitor the dynamic response of an in-service interstate bridge (North-bound span, 1-10 at University Blvd., Las Cruces, New Mexico). Fiber Bragg grating sensors were attached on four different support girders in groups of three at various locations along the span of the bridge. Using an interrogation approach based on the scanning Fabry-Perot system, the sensors were monitored for various vehicle loading conditions. They dynamic response of the bridge to a typical traffic load event as detected by a group of three sensors on a particular girder is illustrated in some detail by describing the data both in time and frequency domains. This is followed by a description of the response of all 32 sensors on the bridge to two traffic loading events. The field test results indicate that the natural resonant frequencies of the first two longitudinal modes of the bridge are 2.5 Hz and 3.8 Hz, respectively. The preliminary results reported clearly demonstrate that an optical FBG sensor system is ideally suited for monitoring weigh-in-motion traffic events as well as for providing the dynamic properties of bridge structures.