The Sydney Harbour Bridge was officially opened on 19 March, 1932. Ninety years later, it remains a stalwart of Sydney Harbour and an iconic piece of Australian engineering.
The bridge’s opening ceremony, which attracted hundreds of thousands of onlookers, was infamously interrupted by a horse-riding, sword-wielding protestor who preemptively cut the ribbon ahead of NSW Premier Jack Lang.
But there’s even more to the bridge’s engineering history than people might realise.
Although the ‘turning of the first sod’ was the first act of construction on the world-famous landmark, in 1923, the planning process began many years before, Deputy Chair of Engineers Heritage Sydney and Engineers Australia Fellow Bill Phippen FIEAust said.
“We’re marking the ninetieth anniversary of the ribbon cutting, but in many ways as engineers we should be thinking about the centenary [of planning],” he said. “Tenders were called in September 1921, more than one hundred years ago.”
The bridge was inspired by the Hell Gate Bridge in New York City, but was decidedly an Australian endeavour.
Project design was spearheaded by Australian engineer John Bradfield, the first man to receive a Doctor of Science in engineering from the University of Sydney.
“The bridge is so strongly associated with one man,” Phippen said. “Clearly lots of other people worked on it, but… it’s Bradfield’s bridge.”
A structure for millennia
Engineers Australia fellow and Executive engineer Greg Evans FIEAust EngExec, who was previously the Director of Asset Maintenance at Roads and Maritime Services NSW, said that the approach engineers take to maintain the bridge is unique in structural engineering.
“It’s a forever structure,” he said. “Most bridge structures have a hundred-year timeline, [but] we see the Harbour Bridge as having everlasting life. That’s the philosophy we take to maintain the bridge. Not just for 100 years but for millennia.”
With the bridge consisting of 40,000 tonnes of steel and requiring 80,000 litres of paint a year, maintenance is a massive operation and perpetually ongoing.
“Being a steel structure in a marine environment, the bridge is constantly under attack from salt air and prevailing winds, and that causes degradation of the paint system and the steel underneath,” Evans said.
According to Evans, a large part of engineers’ duties involves assessing damage to the paint surface and making repairs accordingly.
“The bridge and approaches are [multiple] storeys high, so a lot of the effort [of engineers involves] putting in place platforms so [they] can work safely at heights, capture [paint] that they’re blasting off the bridge so that it doesn’t contaminate the environment, and doing it as quietly as possible,” he said.
The biggest danger involved in these repairs is that they take place at such a height — but safety was not always the priority it is today.
Watching video footage of construction, Evans observed workers leaping from arch to gantry and back again with none of the safety precautions we are now familiar with.
“When the bridge was built, the safety of workers wasn’t a key consideration,” Evans said. “As the industry has matured, it’s realised we have to ensure that all workers go home safely.
“In the early days, people would have a brush and paint can and be completely unprotected. Now, we put in place modern gantries… so [workers] don’t need any fall prevention. If we can’t do that, then [we use] sophisticated fall prevention systems.”
National pride
But it’s not only safety standards that have evolved over the decades — the methods of structural maintenance have developed accordingly.
Whereas the bridge’s six million rivets were originally placed manually, robots are now used.
Robotic technology is also used during the repainting process.
“Two robotic arms, known affectionately as ‘Adam and Eve’, carry out the [paint] blasting,” Evans said.
“[They] have the articulation you would have from your shoulder to your elbow to your wrist, with a nozzle on the end that delivers super high-pressure air to remove the four coats of paint on the bridge prior to application of a new, modern paint system.”
In 2022, hundreds of thousands of people cross the bridge every day by foot, car, bike and train, and it remains an impressive feat of civil engineering.
“There are longer bridges, yes, but considering its span and its width… it is much wider than any other major bridge in the world,” Phippen said. “You could probably get away with saying it’s the largest bridge in the world.”
Evans added: “It’s truly something to take pride in as a Sydneysider — and as an Australian.”