Monitoring dynamic behaviour of a long-span railway bridge

A new long-span prestressed railway bridge was instrumented to better understand and monitor its dynamic behaviour. The bridge is a unique and geometrically complex concrete structure with a very slender box girder section and a slab track system. This paper briefly describes the instrumentation used for monitoring the structural behaviour and focuses on investigating the dynamic characteristics of the bridge. The bridge's dynamic properties were estimated using the output only stochastic subspace identification technique – for which the theory and analysis technique are briefly described – together with more traditional peak picking methods. Natural frequencies of the bridge were identified and verified from a previous study. The obtained frequencies and damping ratios are to be used in updating the developed finite element model. In addition, extreme bridge acceleration values from different train passages were collected and compared with the recommended limit value in bridge design codes.