"If workers were adjusting cables once the bridge was in place, the cables should not have connected to the bridge’s structural integrity, Verrastro said. “Once you’re done tensioning those cables, you’re done,” he said.
It’s possible the cables were over-tightened, causing the bridge to elevate slightly in what’s called a camber. Adjusting the cables to address camber would be appropriate, but that would not impact the structural strength.
“If they were adjusting the structural cables, it was to try to put more or less camber,” he said.
Still, adjusting the camber — called tuning the bridge — can be tricky. Robert Bea, a University of California Berkeley engineer and catastrophic risk expert, has studied hundreds of structural failings including the BP Deepwater Horizon. According to Bea, when workers adjusted the camber on a bridge in Australia in the 1970s, it also collapsed.
{West gate bridge} “The steel buckled while they were attempting to tune this camber, so it’s very plausible,” he said.
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The bridge’s superstructure was something Verrastro said he’s not seen in 42 years of designing bridges. Rather than using steel trusses, it employed heavier concrete trusses. The bridge also had a concrete roof, adding even more weight. “This was a very long span and then they used very heavy material,” he said. “The majority of pedestrian bridges are steel.” Steel bridges are about one-tenth the weight of concrete, he said.
copy pasta from
http://www.miamiherald.com/news/local/community/miami-dade/article205422719.html