Structural Awards 2012: West Gate Bridge Strengthening
Posted by Ram Kumar Shrestha on December 17, 2012
This $400m project involved strengthening and widening the bridge from four to five lanes. The work was extremely demanding, both analytically and physically. Design of the strengthening of the steel bridge needed complex non-linear finite element analysis, and the work involved access to very confined spaces. Strengthening of the concrete box girders involved additional external pre-stressing cables, and extensive application of carbon fibres.
“This project is an exemplar of the vital contribution of structural engineering excellence in sustaining and extending the life of our critical aging infrastructure. The diversity of technical, management, environmental and construction challenges faced by the team on this landmark project were simply breath-taking. Its success is a testament to their structural engineering skill and tenacity. The teams’ ability to build upon engineering first principles and pioneer innovative new strengthening techniques were fundamental to realising the objectives of the project.”
“The West Gate Bridge is an extradosed bridge in Melbourne, Victoria, Australia. It spans the Yarra River, just north of its mouth into Port Phillip, and is a vital link between the inner city and Melbourne’s western suburbs with the industrial suburbs in the west and with the city of Geelong, 80 kilometres (50 mi) to the south-west.
The main river span is 336 metres (1,102 ft) in length, and the height above the water is 58 metres. The total length of the bridge is 2,582.6 metres (8,473.1 ft). It is the third longest in Australia behind the Houghton Highway and the Hornibrook Bridge, and is twice as long as the Sydney Harbour Bridge.
The bridge passes over Westgate Park, a large environmental and recreational reserve created during the bridge’s construction (Wikipedia).”
“‘… the most tragic industrial accident in the history of Victoria.’
(Report of Royal Commission into the failure of West Gate Bridge, VPRS 2591/P0, unit 14)
At 11.50 am on 15 October 1970, a 367-ft (112 m) span of the West Gate Bridge, known as span 10–11, collapsed during construction. Approximately 2000 tonnes of steel and concrete came crashing down into the muddy banks of the Yarra below, taking workers and their machinery, tools and sheds with them.
Thirty-five workers lost their lives that day: many others were injured. Most victims were those working on top of the bridge at the time of the collapse. Some men were lucky enough to be on their morning break away from the site; others simply ran out of the way before the bridge fell on top of them (Victorian Archives Centre).”
Wednesday, October 14, 1970: The unbolting of 4-5 Splice on 10-11 North
“On Wednesday 14th October, Ward (D Ward, M.I.C.E., Section Engineer, Freeman Fox and Partners, West Side ) gave formal written instructions for work to be done (to straighten the buckle on span 10-11 “without further delay”). The instructions refers first to the necessity to complete the bolting of the No. 4 diaphragm; unbolting the 4-5 splice is to be done with the object of making possible the completion of the diaphragm connection.
Work started at about 8.30 am on 15th October. After about sixteen bolts had been loosened, there was significant slipping of the two plates relative to one another such that the loosened bolts were jammed tightly in their holes and could not be removed. At this stage Enness (Senior Inspector of Steel Work for Freeman Fox and Partners) suggested the bolts be tightened with the air gun until they broke. The shock reaction of the bolts failing in tension dislodged the broken pieces and thus cleared the holes.
Eventually about 30 bolts were removed from the box 5 side of the splice, extending from the longitudinal centre line to within about 2 feet of the inner web. Also about seven bolts had been removed from box 4 side of the splice, all close to the longitudinal centre line. The bulge had flattened from about 3.5 inches initially to about 1 1/8 inches, but adjacent to the longitudinal centre line the sliding movement was said to have been so great that some holes were completely blind.
At this stage, a dramatic change took place and the signs of distress for which Ward had been on guard suddenly appeared. First the vicious buckle which up to that stage had been limited to the inner upper panel spread into the adjacent two outer upper panels. This was accompanied by the buckling failure of the upper part of the winner web plate.
About this time, Ward and other witnesses say that they felt a gentle settlement of the north half span of the bridge (www.westgatebridge.org).”
Thursday, October 15, 1970: The Collapse
“Ward, at about 11:00 am, tried to contact Hindshaw, telling him that things were not going according to plan and that he (Hindshaw) should come over to the west side as soon as possible. In fact, Crossley (Peter Crossley, B.A, M.I.C.E, Site Engineer, Freeman Fox and Partners) took Ward’s telephone call and went out to find Hindshaw. The rebolting was going well and the buckle had come out sufficiently to render it possible to make the bolted connection between the transverse diaphragm in box 4 and the inner upper flange plate. To do this, however, the diagonal brace had to be removed, because its plastically yielded end palm plates would have otherwise prevented the pulling down of the top plating.
Hindshaw arrived on the West span accompanied by Crossley. Hindshaw rapidly assessed the situation which superficially did not appear to be deteriorating. He was nevertheless gravely concerned with what was clearly a potentially dangerous situation and decided to ask Hardenberg’s advice. Hindshaw telephoned Hardenberg (Gerit Hardenberg, M.C.E., Senior Representative of Werkspoor-Utrecht, Wescon and WSC in Melbourne) and gave him a brief sketch of the situation asking him to come over. The last thing Hardenberg heard on the phone was as if Hindshaw was thinking out aloud, “Shall I get the bods off?”
Almost immediately after that telephone conversation at 11:50 am, span 10-11 collapsed. Among those who died were Hindshaw, Crossley and Tracy (William Tracy, B.C.E, Section Engineer, JHC, West Side) (www.westgatebridge.org).”
Extracts from Report of the Royal Commission into the Failure of West Gate Bridge (1971, Victoria)
Image: “The Manitowoc Herald Times”, Manitowoc, Wisconsin, Thursday, October 15, 1970, page 1.
Bridge Span Collapses; 24 Killed
MELBOURNE, Australia (AP)–Twenty-four workmen were killed and 19 injured today when a 2,000-ton section of a bridge under construction in Melbourne fell 134 feet to the ground. Twenty-five other workmen were missing, authorities said.
The collapse halted work on what is to be Australia’s largest bridge, over a mile long spanning the Yarra River in the southern part of Melbourne. Known as the West Gate Bridge, its eight lanes are expected to carry 30,000 cars and trucks daily. Completion was scheduled for next year.
Within hours of the accident, unions withdrew their men from the $47 million project and Premier Sir Henry Bolte of Victoria State ordered an investigation into the disaster.
About 70 welders were on the prefabricated steel and concrete span when it gave way and thundered down on construction sheds along the riverbank where other workers were eating their lunches.
A fire broke out, and fire engines and every available ambulance were ordered to the scene. Three huge mobile cranes were moved in to lift debris.
“The bloody thing cracked in the middle,” said one of the injured welders. “I was on top of it.”
Work on the bridge was halted temporarily two months ago so that its steel framework could be strengthened. This followed the collapse of part of the similarly constructed Milford Haven Bridge in Wales on June 2 in which four men died. The consulting engineering firm of Freeman Fox and Parners was employed on both projects.
Image: Sketch of the collapse from the inquest files
VPRS 24/P3 Inquest Deposition Files, unit 120. Source:http://www.prov.vic.gov.au/exhibs/westgate/024-p3-120-010-150-02.htm.
Thursday, October 15, 1970: The Aftermath
“The scene was one of utter devastation. Emergency services responded quickly and together with nurses, first-aid staff, and other volunteers, worked all day and into the night to search for survivors and account for the dead.
‘Rescuers worked all afternoon and far into the night, always in horrifying conditions, often in peril of death or injury themselves. A fire broke out as a result of spilled diesel oil igniting; while quickly extinguished, the fire added to the difficulties of rescue work … All that was humanly possible to save life and mitigate the suffering of the injured, was undoubtedly done.’
(Report of Royal Commission, VPRS 2591/P0, unit 14)
An expert technical committee was immediately established to investigate the scene. The following morning, amid nationwide grief and horror, then Premier Sir Henry Bolte announced the establishment of a royal commission to investigate the cause of the collapse. Its report, tabled in parliament in 1971, left no party associated with the collapse blameless and stated that:
‘Error begat error … and the events which led to the disaster moved with the inevitability of a Greek Tragedy.’
(Report of Royal Commission, VPRS 2591/P0, unit 14)
The government’s involvement in the West Gate Bridge project, from its conception in the early 1960s through to its troubled construction and eventual completion in 1978 is documented across several agencies, ministerial portfolios and statutory bodies (http://www.prov.vic.gov.au/exhibs/westgate/disaster.htm).”