Viability of optical tracking systems for monitoring deformations of a long span bridge

Abstract

Characterisation of both dynamic and quasi-static deformations of suspension bridges is essential to manage their serviceability and to appreciate the internal forces due to the various live loads effects of wind, temperature and traffic. GPS is commonly used for the largest, most flexible structures but the limitations are not well understood and accelerometers cannot capture the extreme low frequency movements. Optical displacement tracking has potential to avoid all these errors but has different types of limitation that need to be evaluated and mitigated. In attempt to cross-validate optical tracking technology against GPS data, a commercial optical system the Imetrum ‘Video Gauge’ was used at Humber Bridge, after first initial experiments on a short span bridge to identify the most effective way to deploy it in the field for measurements at very long range. Some results are presented illustrating the character of the observed deformations and the limitations of the various forms of deformation monitoring instrumentation. In particular limitations of GPS were highlighted through comparison with Video Gauge and accelerometer data.