NTSB secures sections of FIU bridge for closer look as investigation continues

Federal transportation investigators have identified sections of the Florida International University bridge for closer examination and moved them to a secure location.

As they try to determine why a 950-ton span collapsed suddenly on Thursday, killing six people, investigators will likely pull plugs of concrete from the sections to determine whether they meet safety standards and design criteria, National Transportation Safety Board spokesman Christopher O’Neil said. While some bridges are reconstructed following failures, O’Neil said the FIU construction made it impractical to rebuild.

“We’ll really look at specific items key to understanding the design and integrity to see what might have failed,” he said.

In the coming days, investigators will also interview all the players involved, from construction workers to engineers to those whose job was to decide to keep traffic flowing while workers adjusted cables, which could help clarify an escalating blame game between state and local officials.

Monday evening, Gov. Rick Scott posted a tweet saying he had ordered the Florida Department of Transportation to suspend federal payments for the bridge.

“Also just had a great talk with @SecElaineChao, who told me @USDOT inspector general is performing an audit on this tragedy to find answers,” he said.

The cutting-edge bridge, pitched by its creators as a signature addition to the campus and meant to highlight the university’s own “instant bridge” rapid construction program, would have spanned eight lanes of traffic over Southwest Eight Street and the nearby C-4 canal. It was intended to connect the university to housing and help revive Sweetwater’s flagging downtown.

The 174-foot span was constructed alongside the road and hoisted into place a week ago Saturday. But after cracks appeared, chief engineer Denny Pate called a Florida Department of Transportation official the following Tuesday to alert them to the need for repairs. “From a safety perspective we don’t see that there’s any issue,” he said in a message that was not discovered until Friday.

Just hours before the collapse, a meeting was called, but it’s not clear if cracking was discussed. An FDOT official at the meeting said no safety issues were brought up and no requests made to close the road.

Since the collapse, local and state officials have struggled to shift blame, with the FDOT issuing a rare Friday night statement about the missed message and insisting the state’s role was limited.

While what kind of work they were doing before the bridge came down — and the precise sequence of events — remain unclear, NTSB investigator Robert Accetta confirmed last week that workers were adjusting tensioning cables, the network of thick steel cables that act like tendons to strengthen concrete.

They’ll also take a closer look at the bridge’s design and how it was constructed. The design, according to specs submitted by designers to FIU, includes two spans attached to a towering center pier with “stay cable” pipes radiating out, attached to the bridge’s canopy and intended to provide stiffness but not structural support. The span included the web of post-tensioning cables for strength, while a center row of concrete trusses and canopy was supposed to be compressed with high-strength steel cable and bars, according to design documents.

Such designs are more common in Europe than in the United States, O’Neil said.

“We have experience in bridge accidents, but haven’t investigated this type,” he said.

The accelerated construction used to erect the bridge will also be part of the review, he said.

“It all goes hand in hand,” he said. “The design of the bridge lends itself to this type of construction.”

This story was originally published March 19, 2018 at 9:11 PM with the headline "NTSB secures sections of FIU bridge for closer look as investigation continues."