Rapid Displacement Monitoring Using Wireless Hybrid Sensor on an In-Service Highway Bridge

Condition assessment and monitoring of bridges is critical for safe passenger travel, public transportation, and efficient freight. One of the most important parts of a bridge is the expansion joint, which accommodates continuous cyclic thermal expansion of the whole bridge. Conventionally, the displacement of the expansion joints is measured using wired sensors including LVDT, laser displacement transducer, etc. However, implementation of the wired displacement sensors is expensive due to the high cost of the data acquisition system, and time consuming cable installation. To overcome the challenges, a wireless smart sensor network (WSSN) has recently drawn significant attention as an alternative for transportation infrastructure monitoring. The main merits of WSSN are low cost, wireless communication capability, and versatile on-board computation. In this paper, a rapid wireless displacement monitoring system has been developed. This system, named wireless hybrid sensor (WHS), combines a high-resolution analog displacement sensor, a microprocessor, and a wireless multi-scale sensor board for accurate displacement monitoring. The WHS has been calibrated for both static and dynamic displacement measurement in the laboratory environment, and deployed on an in-service highway bridge to demonstrate rapid expansion joint monitoring. The test-bed is a continuous steel girder bridge, the Founders Bridge, in East Hartford, Connecticut. Using the WHS system, the static and dynamic displacement of the expansion joint has been successfully measured. With the WHS system, approximately 6% of the time was spent on installation and 94 % for the measurement.