Design failures are to blame for an overpass across one of Adelaide’s busiest roads shifting, causing safety concerns that closed the road for five days.
The state government has released a report on what caused the damage to the overpass across South Road at suburban Glandore, a shared pedestrian and cyclist path, which came to light in January when debris fell onto the road below.
Transport Minister Stephen Mullighan says the report from engineering firm Aurecon shows the incident was a result of "a failure of the design" of the bridge, which did not meet Australian standards in three different areas.
"It's very concerning from the government's perspective that we have got what is a failure of the appropriate design of the bridge," he told reporters on Monday.
"This is unacceptable from a series of companies who are very experienced nationally and internationally at delivering infrastructure projects."
The report said the bridge was not designed to properly allow for it to bear more weight on one side than another, caused by a row of "anti-throw screens" lining one side of the bridge to prevent people from throwing objects as passing cars.
It said this uneven load was exacerbated by southerly winds against the screens, and led to the bridge's bearings moving out of position.
Aurecon's report made four recommendations for minimising further damage to the overpass and returning it to working order.
Mr Mullighan said the first recommendation, to take the anti-throw screens off the bridge, was already underway with some screens coming off on Monday.
He said Aurecon would also help drive the permanent fix of the overpass and complete a detailed review of how the government inspects and maintains SA's bridges.
The overpass was built in 2009 under a design and construction contract with McConnell Dowell, through which engineering firm AECOM designed the bridge and Wallbridge and Gilbert Consulting and Engineers certified it.
Mr Mullighan said the government would ask the group of companies how the failures could have happened and would ensure they "make good" on the overpass.