MiamiHerald / If tightening support cables caused Florida International University’s signature new pedestrian bridge to collapse, as Sen. Marco Rubio has suggested in a tweet, the rubble spread across the Tamiami Trail could contain obvious clues, bridge experts said Friday.
Adjusting tension cables, which ran like tendons through the 950-ton concrete span and the trusses that held up a concrete canopy on the bridge, can be a delicate operation. Over-tightening the cables, which are used to reinforce the concrete, can have devastating results, the experts say: It might cause torquing, or twisting, that would cause a specific cracking pattern in the concrete on impact with the road, something investigators would likely detect quickly.
Late Friday, National Transportation Safety Board investigators confirmed that crews were tightening tensioning cables in a diagonal truss at the north end of the bridge on the day of the collapse. But they stressed they did not know whether that was the point at which the span failed.
That’s just one of a myriad possible causes for the failure of the unfinished bridge, which crumpled to the pavement on Thursday, claiming a toll of six dead to date. Late Friday, five cars, possibly holding more victims, remained under the debris.