Timber Bridges in Local Government – Part of the Solution not the Problem

Abstract

Local governments own almost all of the remaining timber bridge inventory in Australia. Some estimates place the total number of timber bridges in Australia still in service at 42,000 counting highway, jetty’s, pedestrian and railway bridges. The average age of these timber bridges is continuing to increase with a significant block of the timber bridges having an average age of 82 years. Local governments often have large numbers of timber bridges typically on low volume roads and are associated with unsustainably high replacement costs in Asset Management Plans. Further, they have little training in dealing with timber bridge renewal and restoration. The typical method of dealing with this aging population of timber bridges has been to retain outside consultants who themselves have little training in timber design and timber bridges. For decades the undergraduate training programs for Australian engineers has contained little or no formal training in timber design and inspection. Further, only a handful have any wood technology training that would provide the necessary background to justify their role in working with local governments to conduct inspections, design restoration solutions, develop maintenance plans and undertake renewal of these bridges. State authorities have very few timber bridges left in their inventory and consequently there is little value for them in developing new timber bridge maintenance standards. Asset managers typically value the timber bridge inventory renewal process by replacement with concrete bridges. The typical method of dealing with timber bridges has been to prioritize the inventory for replacement and downward rate the remaining timber bridge inventory. Today with so many of these timber bridges supposedly needing to be replaced or down rated communities can’t function effectively on the road network. Local governments face costs that are out of reach. With an average age for timber decks from 15 – 35 years, asset managers are finding it hard to justify any expenditures for timber bridges beyond replacement with concrete. The result; further poor quality maintenance and downward load rating of timber bridges due to poor maintenance practices. This publication tells the story of one such Council in Northern Queensland in the worst decay, termite, exposed corrosion an embedded corrosion zones in Australia who faced this situation. Six years ago they had 69 timber bridges that were identified as the number one risk to the community in Transport Assets. They responded by having their timber bridge management and maintenance staff get educated as to how to properly inspect timber bridges, maintain and restore them and renew them. They learned how to reduce cost, extend life and utilize the residual assets that still had life in them in all their timber bridges. Along the way they won the prestigious IPWEAQ 5 to 10 million dollar project award for their restoration of 11 concrete/timber bridges on one road that were restored with timber, saving millions for their community. Their story is a story that everyone managing, maintaining and restoring timber bridges will want to hear.