Timber bridge maintenance optimisation

Timber bridges remain a significant proportion of the bridges on the New South Wales classified roads system, notwithstanding the age of these structures and the advent of many more modern structural forms and advances in the use of materials such as concrete and steel. As at June 1992, there were 915 timber bridges out of a total bridge stock of 5742 (833 timber post and beam, 82 timber truss). A significant number of these bridges are structurally deficient and/or nearing the end of their expected in-service life. However, replacement of these bridges would require a massive capital investment and, based on the current replacement programme, the majority of the State's existing timber bridges will need to be maintained for many years to come. Strengthening and rehabilitation of timber bridges will be necessary if these structures are to remain in service. A timber bridge maintenance optimisation study was initiated with the aim of determining how this is to be achieved in the most cost effective manner. This study has resulted in a proposed new approach to timber procurement, a new draft specification for supply of timber, recommendations on preservative treatments and a number of details to improve the performance of timber bridges.