Bridges

The aim of this paper is to share the experience in managing the risks facing a 125 years old Hampden Bridge which is a unique road suspension bridge in Kangaroo Valley, New South Wales. It was built in 1897 and this is a load-deficient bridge which is required to carry one lane of current legal loads. This paper covers all aspects of the original design, the strengthening and rehabilitation designs following the failure of a few of the critical members, findings from numerous consultant investigations since 1990, inspections with non-destructive tests, load tests and structural health monitoring. This paper also discusses some long-term, sustainable and cost-effective solutions to manage the risk of this bridge by the asset owner.

This bridge underwent a major rehabilitation in 2010 and a significant amount of additional dead load has been added to the original bridge in stages. After this rehabilitation, however, a few critical members were not performing as intended and were failing. This highlighted the need for follow-up investigations to resolve the root cause of these failures for this highly complex long span bridge. Observation of the bridge under usual traffic conditions was required to determine the bridge behaviour and to examine the failure of critical elements.

The Technical Services team in Transport for New South Wales carried out these investigations including structural health monitoring. Based on these findings a short-term and long-term strategy for this bridge is in progress which will assist asset owner to keep this complex bridge in safe operation for the current approved load.