Integration of GPS and Tri-Axial Accelerometer to Monitor the Deflection of Suspension Bridges

During the design phase of bridge certain characteristics are assumed such as traffic and wind load. In reality these characteristics can change for which it is very important to monitor the health of such structure. It is very much essential that any anomalies from the expected deflections to be detected as soon as possible allowing remedial actions to be taken to prevent disaster of consequence. The global positioning system (GPS) is used for various structural deformation monitoring, both for long term deformation as well as instantaneous deflection. The use of real time kinematic GPS (RTK-GPS) now allows sub-centimeter accuracy to be achieved at a rate of 20Hz maximum and distance from the reference receiver to the bridge receiver of 20km. This makes the system capable of detecting the deflection of long bridges. In addition accelerometers became useful for such monitoring allowing precise readings up to 1000Hz. However both systems have their limitations such as GPS suffers from multipath ambiguity, cyclic slip, low frequency of data and needs good satellite coverage. Accelerometers exhibits drift characteristics. The integration of these two systems results in a hybrid arrangement that helps to eliminate the disadvantages of the two separate units and significantly increase the measurement production and improve the overall system reliability and performance.