Half a century on from one of the country’s worst industrial disasters, the collapse of Melbourne’s West Gate Bridge still haunts members of Australia’s engineering community.
At 11:50 am on 15 October, 1970 a 112-metre span of the West Gate Bridge collapsed during construction, killing 35 people as 2,000 tonnes of concrete and steel fell from the structure. Some of those who died were on their lunch break beneath the bridge, while others were working on top and inside the girder when it collapsed.
The bridge, which is the second-longest in the country, was two years into its construction.
A Royal Commission began two weeks later. Its final report, delivered in August the following year, explained that there were many contributing factors.
“Error begat error” leading up to the collapse, the commission found, and “the events which led to the disaster moved with the inevitability of a Greek tragedy”.
According to the report, the principal factor in the collapse was the steel span design, followed by an “unusual” erection method by contractors for span 10-11 on the western side and 14-15 on the eastern side.
Retired civil engineer and past chair of Engineering Heritage Australia Ken McInnes told create that instead of fabricating transverse box sections, raising them onto a temporary support beam and bolting them together, the contractors assembled two half-girders, jacked them to the top of the columns, and then joined the thin top and bottom flanges to form a completed box section
“When the two halves of the spans were raised and placed together, the longitudinal flanges were unable to be joined and were buckled,” he said.
There was a 110 mm difference in camber where the halves met, which was addressed by 10 eight-tonne blocks of kentledge to try and weigh down the north side. This led to the buckling, with a series of bolts then removed in an unsuccessful attempt to ease this.
McInnes, who had toured the site as a young engineer a couple of months earlier, found out about the disaster on a doctor’s waiting room TV.
“On returning back to the office at Scott and Furphy consulting engineers, we were able to see the site from the roof of our building, and see the missing column and the missing span, and realise the horror of what had happened,” he recalled.
In the shadow
AECOM Australia consultant John Connal MIEAust, who finished a civil engineering degree at University of Melbourne in the year after the collapse and has been a bridge designer since, said the sadness for the lives lost, and even apprehension about the bridge’s safety, still persists among some in the city.
Connal joined Maunsell and Partners — who were joint consulting engineers with the firm responsible for the design of the bridge — in 1981.
“For much of my career at Maunsell, the shadow of the West Gate Bridge failure lingered in the background,” he told create.
“It is said that the collapse led to the early death of Miles Birkett, who was the leader of the firm and who had a direct leadership role in the project.
“Many of the more senior people in Maunsell during my early years at the firm had direct experience on the West Gate Bridge site, and one of the bridge inspectors rode the bridge down and survived.”
There were 18 men who reportedly survived the fall.
“The collapse and the resulting Royal Commission has had a profound effect on the engineering community in Australia, but particularly Victoria and Melbourne,” Connal added.
“I think the bridge design community became very wary of pushing the engineering boundaries and perhaps lost some confidence for a period. The focus on design expertise and competence became sharper.”
University of Sydney Professor of Practice (Bridge Engineering) Professor Wije Ariyaratne FIEAust said there is a universe of difference between a half-century ago and now in terms of bridge building safety.
Design codes, such as AS 5100, are much more comprehensive, Ariyaratne said.
He added that there have been important advancements in construction specifications, technology, onsite construction practices and stringent work health and safety regulations. And there is much more accountability for everybody from the site worker all the way up to the owner, he said.
“As a result of this evolution or development, one of the most important things is the safety in design, which was not there at that time [in 1970],” explained Ariyaratne.
“Any project, it doesn’t matter how small or how big, how simple, how complex: you have to go through this process. There are workshops after workshops after workshops to evaluate the risk. What are the issues that you have incurred in constructing this design? What is the safety? What are the drawbacks?… We have moved a long way in the right direction.”