On this day (Australia): In 1970, a portion of the West Gate Bridge in Melbourne collapsed, killing 35 people

On 15 October 1970, a portion of the West Gate Bridge in Melbourne collapsed, killing 35 people.

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 is a vital link between the inner city (CBD) 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. It is part of one of the busiest road corridors in Australia.

The main river span is 336 metres (1,102 ft) in length, and the height above the water is 58 metres (190 ft). The total length of the bridge is 2,582.6 metres (8,473 ft). It is the fifth-longest in Australia, the longest being Melbourne’s Bolte Bridge at 5 kilometres (3.1 mi).

The West Gate Bridge is twice as long as the Sydney Harbour Bridge and is one of the highest road decks in Australia, clearing the water at 58 metres (190 ft), with the Sydney Harbour Bridge clearing the water at 49 metres (161 ft).

The bridge passes over Westgate Park, a large environmental and recreational reserve created during the bridge’s construction, and carries up to 200,000 vehicles per day.

Collapse

Two years into construction of the bridge, at 11:50 am on 15 October 1970, the 112-metre (367-foot) span between piers 10 and 11 collapsed and fell 50 metres (164 feet) to the ground and water below.

Thirty-five construction workers were killed and 18 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 2,000-tonne (4,400,000 lb) 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 20 kilometres (12 mi) away.

On the following morning, 16 October, Sir Henry Bolte (Premier of Victoria) announced that a Royal Commission would be set up immediately to look into the cause of the disaster.

The 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

A Royal Commission into the collapse was established, which 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 11.4 centimetres (4.5 in) 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 t (8.8 short tons), 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 came through to remove the buckle. As the bolts were removed, the bridge snapped back and the span collapsed.

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 to workers who lost their lives is located near the bridge. It opened on 15 October 2004, the 34th anniversary of the collapse. It includes the existing West Gate Bridge Memorial and Sculpture, and the memorial for six who died in the Spotswood Yarra Sewer Tunnel collapse of 12 April 1895 (Good Friday).

Source: Wikipedia