Thousands of timber bridges crossing rivers and creeks and linking isolated communities to the rest of Australia are in serious disrepair but local councils cannot afford to fix or replace them all. Source: The Sydney Morning Herald
Now, a simple low-cost procedure developed at an Australian university could help councils better manage their ageing infrastructure by providing reliable information about a structure’s condition and the loads it can carry safely.
Traditional load testing costs about $5000 for each bridge span, according to researchers at the University of Technology, Sydney (UTS).
In contrast, a new procedure developed by UTS Professor of Structural Engineering Keith Crews and his team, which uses a technology based on measuring the vibration of a bridge deck, costs only $850 per span – and delivers more reliable information.
Originally requiring sophisticated electronic equipment, these vibrations can often now be measured using apps on a smartphone.
Recent surveys indicate there are more than 40,000 bridges in Australia. About 27,000 of them are made of timber, most of which are at least 70 years old.
Most of these timber bridges are on regional roads, owned and maintained by local authorities, which are often under-resourced and lack the engineering expertise to undertake strength testing of their bridges.
According to the NRMA, there is a $3.87 billion backlog of work needed to bring NSW council roads, including bridges, up to a “satisfactory condition”.
The UTS procedure relies on accelerometers that measure vibration on a bridge. The vibration depends on the number of spans on the bridge and the dynamic stiffness of the bridge’s deck.
Timber strength is also taken into account and especially developed algorithms are used to correlate stiffness properties to bridge strength.
When researchers in the Faculty of Engineering and IT at UTS started this research about 10 years ago, they visited regional and rural areas with a “truckload of gear” and would spend about a week assessing a single-span bridge.
“Now we can often test six to eight spans in a day and, although we continue to use some specialist equipment, we can often get basic data with a mobile phone,” said Professor Crews.
“We want to develop this technology to a point where councils can do the work and we provide technical support and training to their staff and their consultants.”
To that end, Professor Crews and his team are talking to the Institute of Public Works Engineering Australia about the best ways to train council staff to use the new procedure.
Engineers are often trained to build things, not to repair them, said Professor Crews.
“We need to make sure that engineers understand that infrastructure ages and we have to manage that.
“We want to build confidence and competence among local government to manage their ageing timber bridges and give them the back-up they need.”
