West Gate Bridge
The West Gate Bridge is a steel, box girder, cable-stayed bridge in Melbourne, Victoria, Australia, spanning the Yarra River just north of its mouth into Port Phillip. It carries the West Gate Freeway and is a vital link between the Melbourne central business district and western suburbs, with the industrial suburbs in the west, and with the city of Geelong to the south-west. It is part of one of the busiest road corridors in Australia. The high span bridge was built to allow large cargo ships to access the docks in the Yarra River.
The main river span is long, and above the water. The total length of the bridge is. It is the fifth-longest in Australia, the longest being Melbourne's Bolte Bridge at. The West Gate Bridge is twice as long as the Sydney Harbour Bridge and is one of the highest road decks in Australia, higher than Sydney Harbour Bridge's. It carries up to 200,000 vehicles per day.
The bridge passes over Westgate Park, a large environmental and recreational reserve created during the bridge's construction.
Transportation
Motor vehicles
The West Gate Bridge is a 10-lane dual-carriageway freeway bridge, carrying five lanes of motor vehicle traffic in each direction. The freeway corridor carries a very high volume and occupancy of traffic; a total of between 180,000 and 200,000 cars, trucks, and motorcycles use it per day, according to VicRoads. This makes the West Gate Bridge and West Gate Freeway one of the busiest road corridors in Australia.As it is the only main direct link between Melbourne's CBD and the west, it is frequently congested during the morning and afternoon peaks and is constantly busy due to the number of vehicles coming in and out of the Port of Melbourne. The bridge was originally tolled but John Cain's government made a promise at the 1985 election to discontinue tolls; this came into effect in November of that year.
The bridge is windswept as there are no significant obstructing terrain features for some distance, particularly in the quadrant from south to west, a common wind direction. This can lead to issues for motorbikes, trucks and other high-sided vehicles in higher wind speeds. Previously wind warning lights were present at the bridge approaches to control traffic, but the former practice is to reduce the speed limit to or when the wind speed gets too high. This has since been replaced with a modern variable speed limit system as part of the 2008–11 upgrade.
Cycling
Cyclists are prohibited from using the bridge except for special bicycle events, notably the Melbourne Summer Cycle, a fundraising event for multiple sclerosis, and the Around the Bay in a Day event that raises money for The Smith Family charity. The Westgate Punt is a foot ferry that runs directly below the bridge, taking cyclists and pedestrians across the Yarra between a jetty at Fishermans Bend near Westgate Park – Bay Trail and a jetty adjacent to Scienceworks Museum – Hobsons Bay Coastal Trail. It operates on demand, from Monday to Friday in morning and evening peaks, and on weekends and public holidays from 10:00 am to 5:00 pm.History
Proposals and realisation
The notion of a Lower Yarra River Crossing has formal origins as early as 1888, when Victoria’s Public Works Department first proposed a tunnel under the Yarra. The Metropolitan Town Planning Commission's Plan of General Development proposed a bridge for a road between Geelong Road and Ingles St, Port Melbourne. Road routes between central Melbourne and the west were, however, bridged further north, and the usual method of crossing at the lower Yarra was via skiffs until 1912, when ferries were first instituted, the Newport steam ferry operated by the City of Williamstown taking prominence between 1931 and 1974.The Western Industries Association was formed in August 1957 and claimed to be ‘representative of all industries in Altona, Footscray, Sunshine, Werribee and Williamstown districts’. Having formed a sub-committee to investigate a Yarra crossing, in 1958 it asked Victorian Premier Henry Bolte ‘to give urgent consideration to construction of a traffic tunnel under the Yarra.’ The Association had been told by 'shipping interests' that a bridge would not be acceptable for the crossing. The tunnel, it was suggested, would carry 30000 cars a day; differing estimates on the capacity of the 'overtaxed' ferry suggested it could only handle between 1200 and 2000. The Victorian Government's response to the proposal, delivered by Commissioner for Public Works Thomas Maltby, was that the government's finances were inadequate to undertake a crossing urgently and that any such project would require private investment. In 1961 Lower Yarra Crossing Limited was formed, a non-profit company to develop the crossing. In mid-1960 it was announced that the Association would raise the money to construct the bridge with government support keeping interest rates low; the arrangement was envisaged as not, in itself, profit-making. In this year, the Western Industries Association applied to government for license to construct and operate a crossing on a toll basis.
In 1961 the Association formed Lower Yarra Crossing Ltd. Test drilling began late in that year by which point the Association once again became publicly open to the construction of a bridge, rather than a tunnel. Nevertheless Danish tunnel engineering firm Christiani and Nielson were engaged as consultants. Chief amongst the concerns regarding a tunnel was the limitation on particular goods or cargoes - notably, flammable material - that could legally, or safely, be carried through a tunnel.
In the state government's analysis, the cost of building a bridge or a tunnel would be equal, however, notwithstanding the Harbour Trust's strong advocacy for a tunnel, it was felt by those in power that a bridge would more readily allow use by petrol tankers. In 1965, Yvonne A. Van Den Nouwelant writes, ‘the Lower Yarra Crossing Authority was granted a franchise by Act of Parliament and in 1968 construction started on the West Gate Bridge.’ It was noted by the press at the time that the location of the bridge's eastern approaches would require the removal of the Fishermen's Bend airstrip.
Collapse
Two years into construction of the bridge, at 11:50 am on 15 October 1970, the 112-metre span between piers 10 and 11 collapsed and fell 50 metres to the ground and water below. Thirty-five construction workers died and eighteen were injured, and it remains Australia's worst industrial accident. Many of those who died were on lunch break beneath the structure in workers' huts, which were crushed by the falling span. Others were working on and inside the span when it fell. The whole mass plummeted into the Yarra River mud with an explosion of gas, dust and mangled metal that shook buildings hundreds of metres away. Nearby houses were spattered with flying mud. The roar of the impact, the explosion, and the fire that followed, could be clearly heard over away. On the following morning, 16 October, the Premier of Victoria, Sir Henry Bolte, announced that a Royal Commission would be set up immediately to look into the cause of the disaster. Prime Minister John Gorton, said: "I am sure the whole of Australia is shocked and saddened by the serious accident at West Gate Bridge. Please extend my deepest sympathy to all those families to whom this tragic event has brought such grief."Cause
The Royal Commission concluded on 14 July 1971. It attributed the failure of the bridge to two causes: the structural design by designers Freeman Fox & Partners, and an unusual method of construction by World Services and Construction, the original contractors for the project.On the day of the collapse, there was a difference in camber of between two half-girders at the west end of the span which needed to be joined. It was proposed that the higher one be weighted down with 10 concrete blocks, each weighing 8 tonnes, which were located on-site. The weight of those blocks caused the span to buckle, which was a sign of structural failure. The longitudinal joining of the half-girders was partially complete when orders were given to remove the buckle by unbolting the upper flange along the splice between boxes 4 and 5, allowing the plates forming the upper flange to slide over one another. The removal of the bolts created a stress concentration that the bridge could not withstand, owing to inadequate factors of safety in the design. The bridge collapsed approximately an hour later.
Collapse memorials
Six twisted fragments of the collapsed bridge can be found in the West Gate garden at the engineering faculty of Monash University, Clayton campus. The university acquired them after being asked to participate in the investigation of the collapse. It is said that they are to remind engineers of the consequences of their errors.Commemorations have been held on 15 October every year since the collapse. A West Gate Bridge Memorial Park is located near the bridge. It opened on 15 October 2004, the 34th anniversary of the collapse. It includes the West Gate Bridge Memorial and Sculpture, and the memorial for six who died in the Spotswood sewer tunnel collapse of 12 April 1895.
Completion
Three other steel box girder bridges collapsed during their construction between 1969 and 1971: the Fourth Danube Bridge in Vienna on 6 November 1969; Cleddau Bridge, Wales on 2 June 1970; and the South Bridge over the Rhine River in Koblenz on 10 November 1971. The UK government responded by setting up the Merrison Committee of Inquiry, headed by Sir Alec Merrison. The Merrison Committee provided an interim report in May 1971, and a final report in February 1973 on new design and workmanship rules for steel box-girder bridges.Following the publication of the Report of the Royal Commission in August 1971, the Lower Yarra Crossing Authority, a non-profit company, formed its own Directorate of Engineering. In September 1971, Hans G. Wolfram, FIEAust and a Director of Gutteridge, Haskins & Davey, was appointed the Director of Engineering. He was responsible for the re-design, supervision of construction, and contract administration of West Gate Bridge until its completion. The Chairman of the Lower Yarra Crossing Authority was Oscar G. Meyer. The Deputy Chairman was Bernard J. Callinan, who was also Chairman of the Technical Committee. In 1971, the Authority was renamed as the West Gate Bridge Authority.
Intensive reviews of the structure focused attention on the inadequate strength of the original design of the bridge's deck. This consisted of a 100 mm reinforced concrete slab acting compositely with a steel deck plate stiffened by bulb flats. Numerous proposals were examined and Wolfram recommended replacing the original steel and concrete deck by a lighter and stronger orthotropic steel deck as technically and economically the most appropriate solution. This orthotropic deck is a steel plate stiffened longitudinally by closely spaced cellular troughs and laterally, at intervals, by cross beams. The proof engineer was Karlheinz Roik, a professor of steel construction at TU Berlin. He independently checked the re-design of the West Gate Bridge in accordance with the recommendations of the Royal Commission. The re-design was also checked against the German code DIN 4114 and the Appraisal Rules of the Merrison Committee's reports. The re-design was endorsed by four other university professors of civil engineering: F.B. Bull, N.W. Murray, J.W. Roderick and L.K. Stevens.
Construction resumed in 1972 with World Services and Construction continuing to fabricate the boxes and to carry out their sub-assembly, but with a joint venture between Redpath Dorman Long and John Holland completing the construction of the steel portion of the bridge. Additional strengthening of the structure had to be designed for the erection because the stresses could exceed those of the in-service condition. The joint venture contractor engaged Flint and Neill of London for this and their design was proof-checked by the Directorate of Engineering.
Charles, Prince of Wales visited the West Gate Bridge project in October 1974 and met with members of the West Gate Bridge Authority and workers.
After 10 years of construction, the bridge was completed in 1978 at a cost of $202 million.
Speed cameras were erected on the bridge in 2004, but were not activated until September 2005, because of issues with a similar camera on the Western Ring Road. However these speed cameras were switched off in 2005, and currently remain disabled, as the sway of the bridge prevents secondary verification of the alleged speed against a fixed point. In 2006 the State Government spent $1.3 million on erecting railway style boom barriers at each entrance to the bridge to block traffic in the event of a terrorist attack. In March 2007, the State Government announced that two flagpoles would be erected atop the main bridge pylons, to fly the Australian and Victorian flags, each being in size and above sea level. Costing $350,000 to install and $15,000 a year to maintain, the flags were unfurled on 24 September 2008.
On 5 August 2007, it was reported that the Victorian Government was planning a $240 million project to identify and eliminate structural weaknesses in the bridge, with specific concerns including crash barriers, cracking, corrosion and potential buckling. News of the work was prompted by the collapse of the I-35W Mississippi River bridge in Minneapolis. Experts were reported as saying the West Gate was initially designed to carry loads of but now carried B-double trucks weighing up to. The bridge was built to carry 40,000 vehicles a day but volumes had grown to more than four times the original number, approximately 160,000 vehicles on an average day.