ABSTRACT
There is estimated to be over 11,000 timber road bridges owned by Local Government in Australia today. The majority were constructed in the second half of the 19th century and the first half of the 20th century as simple girder bridges with spans up to around 10-12m. Bridge lengths varied from single spans up to viaducts several kilometres in length. The bridges utilised Australia’s then plentiful supply of exceptional quality hardwood which could generally be sought close to the bridge site. Today, a substantial number have fallen into disrepair. This is particularly so for the timber bridges owned by Local Government due principally to lack of sufficient funds and increasing shortage of good quality hardwood. The fact that until recently there has been no Australian Standard for the design of timber bridges has also been an issue. Recent studies have indicated that approximately 30% of Local Government timber bridges are in a “poor” to “very poor” condition. To make the required step change a collaborative public-private solution is recommended. These defective bridges represent a “Whole of Government” long-term community safety risk. The reality is that timely replacement of Local Government bridges is simply not provided for in Local, State or Federal Government capital programmes. The author is chairman of Australian Standards Committee BD090-08, responsible for the technical input to the new bridge design standard, AS 5100.8 “Bridge Rehabilitation and Strengthening”. This is the first Australian Design Standard to address the rehabilitation of timber bridges. This paper draws on the learnings from the development of this Standard.
