NTSB: Fatal Miami Bridge Collapse Caused By 'A Paralyzing Culture Of Group-Think'
The engineer, designer and inspectors are all responsible for the 2018 collapse of a Miami bridge that killed six people, the National Transportation Safety Board found.
On March 15, 2018, a 950-ton bridge that was supposed to be an architectural landmark crashed to the ground mid-construction, killing five people in cars below, plus one worker. The bridge was intended for pedestrians, connecting the campus of Florida International University in Miami with the neighboring city of Sweetwater, over a busy road. The NTSB, in a board hearing Oct. 22 in Washington, D.C., faulted both the bridge designer, FIGG Bridge Engineers, and various overseers for the debacle.
"The firm severely underestimated demand on the bridge, significantly overestimated bridge’s capacity and incorrectly determined the bridge to be a redundant structure, among other calculation errors," NTSB Chairman Robert L. Sumwalt said.
Illustrations detail FIGG's miscalculations.
"But another structure failed in this accident, the structure of public safety oversight," Sumwalt added. "This structure should have ensured that a qualified, independent firm provide effective peer review of bridge plans, as required. [New Jersey-based engineering firm] Louis Berger was not qualified and produced an incomplete review. When cracks in the bridgework reached unacceptable levels, the oversight structure should have resulted in a suspension of work and in road closures. It did not. Oversight of the project, like the bridge itself, collapsed."
The agency also released a video and additional documents related to the accident.
Last week, in advance of the hearing, the NTSB released 6,000 pages of documents. They detailed a "paralyzing culture of group-think," the Miami Herald reported. Even though alarming cracks in the concrete structure spread and expanded over two weeks, none of the project leaders took action to halt construction, close the road or raise alarms.
The collapse was due to a faulty design by FIGG that left the bridge weak at a key point. FIGG's unique design was made to look like a cable-stayed bridge, but its strength would really come from a traditional truss structure — in this case, two trusses that would connect and create one contiguous bridge.
Because of the focus on aesthetics, it was designed without redundancies; if one part failed, the whole thing could. Using a technique called Accelerated Bridge Construction, components were built just off-site, then transported into place, where work could be finalized while traffic flowed below the bridge.
The NTSB investigation found that Louis Berger, which had been hired to peer-review FIGG's plans, was not actually prequalified for this type of work, but a Florida Department of Transportation website had listed the firm as such. Louis Berger analyzed the overall bridge structure but didn't analyze how it would function during different stages of construction, nor its nodal areas, NTSB found.
"Louis Berger did not identify significant under-design of the bridge," the NTSB said. FDOT, in turn, didn't follow its own rules requiring certification during key points in plan submittals.
Cracks appeared in late February, but FIGG downplayed their significance. The building contractor, Munila Construction Management, FDOT, Bolton, Perez and Associates Consulting Engineers and the FIU went along with FIGG's determination.
The day of the collapse, FIGG ordered crews to tighten internal steel support rods in a diagonal strut to try to close the cracks, even though that amounted to a design change that should have been reviewed. The tensioning action caused the bridge to suddenly collapse on top of cars stopped at a light.
The NTSB has released an abstract of its report, and the final version will be available next week.
As of July, at least 23 subcontractors were involved in legal settlements of at least $42M over the disaster. Munilla Construction Management changed its name and filed for Chapter 11 bankruptcy after losing $200M of potential income from future contracts, as well as its FDOT certifications, Construction Dive reported. Lous Berger was acquired in December 2018 by WSP Global, a Canadian firm.
Criminal charges are still possible, but unlikely. FIU has vowed to rebuild the bridge.