Pedestrian bridge collapse on the Treasure Coast unlikely to happen, experts say

There’s little chance the Treasure Coast would experience a pedestrian-bridge failure similar to Thursday's disaster at Florida International University in Miami, expert bridge engineers said.

Construction methods used for the FIU pedestrian bridge are much different than those used to build pedestrian bridges here, engineers said.

The Florida Department of Transportation is building the $4.6 million Central Railroad Corridor Greenway Pedestrian Overpass over Interstate 95 near the Fellsmere exit. In 2008, FDOT built the St. Lucie County pedestrian bridge over Okeechobee Road as part of a $45 million widening of Okeechobee Road.

“The thing about (the Miami) pedestrian bridge is that it is kind of an innovative design," said George Denti, a bridge engineer who has been building bridges on the Treasure Coast since 1994. "They used accelerated bridge construction methodology, beams that were built off site and brought there.”

More: Miami pedestrian bridge collapses, killing several people, crushing cars

Now an FDOT consultant, Denti is project administrator for the Crosstown Parkway Bridge in Port St. Lucie.

“In the kind of structures that we build on the Treasure Coast, there are a lot of redundancies in the strength of the bridge so that it doesn’t depend on any one component to catastrophically fail," Denti said. "You would have to do a lot to make one of these (Treasure Coast) bridges fail. You may have some settling or cracking in one portion, but not a complete catastrophic failure."

More: Florida International University shared excitement of 'unique' bridge before installation

The I-95 pedestrian walkway is built from prefabricated steel trusses, said Ian Biava, a senior design engineer for the designer, Kansas City-based TranSystems Corp. Consultants. The concrete walkway will be poured onto the deck, he said.

In contrast, the concrete walkway at FIU was prefabricated and lifted onto the structure in one piece, he said.

"We did not pour the deck (for the walkway) when it was on the ground because we didn't want to lift all that weight," said Biava. The method used in the I-95 pedestrian overpass ensures the structure is supporting itself with the steel beams, he said.

Indian River County Administrator Jason Brown said he was assured by FDOT project officials Thursday the pedestrian walkway will be safe when completed next month.

"Anytime there is a tragic event (such as the one in Miami), you take another look at everything," Brown said. "We're confident the structure they are constructing over I-95 will be a safe structure."

Denti said the FIU bridge was built using a method that would require stressing the steel and cable, putting them under pressure to hold the structure together.

“The integrity of these structures is dependent upon that,” Denti said. “This bridge collapsed under its own weight. I think a component of it failed. ... That’s my best guess, not knowing a bunch about it and just seeing the pictures.”

More: Sights and sounds: Pedestrian bridge collapses at Florida International University

In conventional construction, there would have been warning signs a “total failure” would happen, Denti said.

“You would see some cracking, some stress — something would be moving,” he said.

The Federal Highway Administration rates all road bridges each year for structural soundness, based on National Bridge Inspection Standards.

On the Treasure Coast, four bridges — three in St. Lucie and one in Indian River — are considered structurally deficient by federal bridge inspectors.

In Indian River, the Eighth Street bridge over the Lateral C Canal received the "structurally deficient" designation. In St. Lucie, it's bridges on McCarty and Gordy roads crossing Ten Mile Creek and the D.H. "Banty" Sanders Bridge over the Intracoastal Waterway.