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NTSB Points Blame in FIU Bridge Collapse

Monday, October 28, 2019

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Last week, the National Transportation Safety Board said that, in its hearing, it found that the probable cause of the fatal pedestrian bridge collapse at Florida International University in March 2018 was related to load and capacity calculation errors made by FIGG Bridge Engineers Inc.

The NTSB also alleges that the consulting engineer Louis Berger’s inadequate peer review also contributed to the bridge’s collapse.

FIU Bridge Collapse

FIU is home to the Accelerated Bridge Construction University Transportation Center, a multi-university center promoting ABC techniques. The pedestrian bridge was touted as an example of innovative design and construction meant to limit road closures and inconvenience stemming from the otherwise lengthy bridge construction process.

According to CNN, shortly after the span was installed, W. Denney Pate, employed with FIGG, which was part of the design-construction team, noticed there was an issue—a crack had formed along the north side of the bridge, and repairs were needed. Other engineers, though, had  deemed the structural integrity of the span safe just hours before the incident.

Earlier on the day of the collapse, Miami-Dade Mayor Carlos Gimenez said the bridge had undergone a “stress test." Florida Senator Marco Rubio noted on Twitter that the cables that suspended the bridge had loosened, and the engineering firm ordered for them to be tightened. The cables were being tightened at the time of the collapse.

A few months later, in May 2018, the Miami Herald sued after attempts to access documents related to the collapse, and in early June, FDOT asked a County Circuit Court judge to dismiss the suit. The newspaper said the agency acknowledged that the records fell under the state’s open-records law, but FDOT argued that its pertinence to the NTSB's investigation meant they could not be released publicly.

In August, Leon County state court Judge Kevin Carroll ruled that FDOT must release the records associated with the tragedy. A federal judge, though, quickly stepped in and blocked the release of the documents. In September, a preliminary report from the NTSB indicated that cracks found in the bridge a few days before it collapsed were much more extensive than originally thought.

In April of this year, after MCM filed for bankruptcy, lawyers presented documents alleging that engineers dismissed cracks found in the bridge prior to the disaster. The following month, the construction company responsible for building the FIU bridge reached an agreement with insurers to pay up to $42 million to victims of the incident, as well as their families.

In June, in the 115-page report, federal work-safety investigators determined that the street that ran under the bridge should have been shut down because of cracks in the structure. Parties involved failed to recognize the danger due to design errors. Later that same month, the project’s lead technical designer testified during a pretrial hearing regarding evidence. This was the first time he had commented since the tragedy. In August, other companies being sued in light of the incident decided to settle.

Earlier this month, the NTSB released 6,300 pages of documentation detailing its examination of contractors on the project. One engineer reportedly claimed that the highway underneath the bridge should have been closed while the project was ongoing.

Investigation Findings

Although FIGG and Berger have been identified as the primary contributors to the FIU bridge collapse, the NTSB noted during its Tuesday (Oct. 22) public board meeting that MCM, Bolton Perez and Associates Consulting Engineers, FIU and the Florida Department of Transportation's failure to cease bridge work and close the SW 8th Street to protect public safety also contributed to the severity of the collapse’s outcome.

“Errors in bridge design, inadequate peer review and poor engineering judgment led to the collapse of this bridge,” said NTSB Chairman Robert Sumwalt. “The failure of all concerned parties, to recognize and take action on the threat to public safety presented by the significant observed bridge structure distress prior to the collapse, led to the tragic loss of life in this preventable accident.”

Throughout the investigation, the NTSB found that:

  • Concrete and steel materials used during construction of the bridge were not a factor in its collapse and the hydraulic jack used to post-tension the steel rods in member 11 was operating as expected at the time of the collapse;
  • The restressing of member 11 was a manipulation of loads to address structural cracking of unknown origin, constituting a change to the FIGG design, and the measure should have been independently reviewed by a professional engineer before being implemented;
  • FIGG’s bridge design was nonredundant because it provided only a singular load path;
  • FIGG’s construction plans inconsistently identified when intentionally roughened surfaces were needed to fulfill assumptions of the bridge design;
  • Even if the cold joint surface of nodal region 11/12 had been roughened to a 0.25-inch amplitude, node 11/12 would not have had sufficient capacity to counteract the demand load for interface shear—and the bridge would still have been under-designed and could have failed;
  • The rate of premature concrete distress was clear evidence the structure was progressing toward failure and should have alerted FIGG and MCM to the origin of the distress; and
  • The Florida Department of Transportation should have verified Louis Berger’s qualifications as an independent peer review firm as part of FDOT’s oversight of local agency program projects.

Of these findings and others totaling 30 discoveries made about the incident, the NTSB issued various safety recommendations to the Federal Highway Administration, the Florida Department of Transportation, the American Association of State Highway and Transportation Officials and FIGG.

However, although dismissed by the federal investigative agency, FIGG hired forensic structural engineering firm Wiss, Janney, Elstner Associates to dispute the NTSB’s ruling. Construction Dive reports that WJE’s investigation identified the failure to build a construction joint at member 11 and roughen the concrete beneath bridge member 11 according to FDOT standard construction specifications was the probable cause of the bridge collapse.

The joint assertions were dismissed when NTSB pointed out that FIGG’s construction plans didn’t consistently identify when roughened surfaces were necessary to fulfill the bridge’s design.

Sumwalt added, “I’ve been on this board for 13 years and I don’t think I’ve seen [an accident] where there’s more finger-pointing between the parties. And, you know, the finger-pointing is correct ... because everyone shares a piece of this accident.”

According to the Herald, the immediate cause of the collapse was due to an order made by FIGG’s top engineer on the project, W. Denney Pat who instructed workers to retension the internal steel support bars as an attempt to close the bridge’s existing cracks.

Steven Prouty, senior highway engineer in the NTSB’s Office of Highway Safety, reports that this decision was a change in design plans that wasn’t reviewed, signed or sealed by a professional engineer.

Overall, the bridge’s failure can be summarized in three parts, according to Sumwalt: from FIGG’s underestimated design, to Berger’s failed review, to all parties involved with the construction failing to recognize the seriousness of the errors and inaction to close the roadway below.

What’s Next

The NTSB plans to publish a full report containing the probable cause, findings and safety recommendations made from its investigation within the next few weeks. A spokesperson from the State Attorney’s Office reports that a criminal investigation into the deaths at the bridge remain open and that it is unknown if a criminal case against contractors will arise.

FIU President Mark Rosenberg also reports that the university intends on building a new bridge between Sweetwater and the campus.

“We have to figure out a way to get that bridge rebuilt,” Rosenberg said. “We will rebuild that bridge. We are committed to that bridge, that bridge will be there, and we will memorialize those who were lost because we feel very deeply about that."

   

Tagged categories: Accelerated Bridge Construction (ABC); Bridges; Bridges; Health and safety; Infrastructure; Infrastructure; NA; North America; NTSB (National Transportation Safety Board); Program/Project Management; Project Management; Safety

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