A new technology is being developed in Australia for large scale processing of corroded metal and dirt-encrusted stone surfaces to aid long-term conservation of the Sydney Harbour Bridge and other large scale structures.
Current maintenance work involves sand-blasting rust, dirt and the existing lead-based paint and then applying lead-free paint to the intricate design of the bridge as it approaches its 90th anniversary.
The project, a collaboration between the Australian National University, ANSTO, NSW Department of Roads and Maritime Services (RMS), University of Sydney, and University of Canberra, is using funds from an Australian Research Council (ARC) grant to $858,000 over three years.
The technology being developed uses a new class of powerful industrial ultrafast lasers that substantially reduces the heat load to the structure. These lasers improve the control of the characteristics of the surface following the treatment for better long-term conservation and will reduce energy costs.
In the early decades, the bridge was cleaned and painted by hand. In the last decade or so, autonomous robots have been developed by the University of Technology, Sydney (UTS) in conjunction with the RMS, to inspect and maintain the bridge, receiving two Engineers Australia awards in the process.
The current project's strategy for conserving the bridge includes developing a robotic system that can inspect, clean, repaint and remove waste from the 134 metre-high structure. The expected outcomes, according to ARC, will be new best-practice laser conservation techniques usable for hand-held and automated systems.
"This will reduce maintenance frequency and cost, restore the beauty of the bridge, retain its engineering significance and provide a baseline process for cleaning of other historical large scale metal and stone heritage objects," the Council stated.
ANSTO, whose role on the bridge it is to undertake stress assessment using x-rays and neutron diffraction, said the new techniques will also offer improved safety and economic benefits in building maintenance as well as scrap reduction for the marine, automotive and aircraft industries.
Image: CROC climbing robot inside the Sydney Harbour Bridge. Source: RMS