Operational deformations in long-span bridges

Abstract

Long-span bridges deform quasi-statically and dynamically under a range of operational conditions including wind, traffic and thermal loads, in varying patterns, at different timescales and with different amplitudes. This chapter describes application of a range of measurement technologies, focusing on response to extreme loads, for suspension bridges over the River Tamar (with 335 m main span) and Humber (with 1410 m man span). It compares the effects of vehicular, thermal and wind loads on these very different structures, showing that apart from rare extreme traffic and wind loads, temporal and spatial temperature variations dominate quasi-static response. The chapter addresses the particular issue of identifying the nature of deformations in long-span bridges during normal operation but over long enough periods to capture typical and extreme conditions, providing a useful comparison of their levels and likelihoods. Observations of deformation data and sensor performance for the two bridges are used to highlight limitations and redundancies in the instrumentation.