West Gate Bridge collapsed mid-construction — 35 died from an error known 4 months earlier

The West Gate Bridge was designed to carry the Princes Freeway across the Yarra River in Melbourne — a steel box-girder cable-stayed bridge with a main span of 336 metres, among the longest of its type in the world. Construction began in 1968 under the direction of the Lower Yarra Crossing Authority, with Freeman Fox & Partners as the design engineers, the same firm that had designed several other major box-girder bridges worldwide.

On 15 October 1970, workers were attempting to join two half-girders on the 112-metre span between piers 10 and 11. An 11.4 cm camber difference meant the two halves did not align. Ten concrete blocks, each 8 tonnes, were placed on the higher half to weigh it down. The weight caused the span to buckle. Workers unbolted the upper flange along a splice to remove the buckle — creating a stress concentration the bridge could not withstand. The span fell 50 metres, killing 35 workers and injuring 18. It remains Australia's worst industrial accident.

The Royal Commission reported July 1971, attributing the failure to inadequate structural design by Freeman Fox and unusual construction methods by World Services. The collapse came just four months after the Cleddau Bridge in Wales — also designed by Freeman Fox — had suffered a similar failure during construction. The UK government established the Merrison Committee, which produced new design and workmanship rules for steel box-girder bridges. The West Gate Bridge was redesigned with an orthotropic steel deck and completed in 1978 at a cost of A$202 million.