‘It cracked like hell.’ Feds say engineers didn’t heed alarms before FIU bridge collapse.
Source: https://www.miamiherald.com, June 11, 2019
By: Andres Viglucci and Douglas Hanks
In a damning new report, federal work-safety investigators conclude that engineers in charge of design and construction of the ill-fated Florida International University pedestrian bridge should have shut down Southwest Eighth Street because of growing cracks in the structure, but failed to recognize the span was in danger of imminent collapse due to design errors.
The 115-page report by the Occupational Safety and Health Administration, obtained Tuesday by the Miami Herald, finds plenty of blame to spread around for the collapse of the bridge last year while under construction.
The report details a catalog of errors ranging from a “deficient” design by Tallahassee-based FIGG Bridge Engineers that led to structural failure, to inadequate oversight by two engineering consulting firms that were supposed to act as a backstop on design and construction, Louis Berger and Bolton Perez and Associates, and a fatal attempt by FIGG to close the cracks that triggered the collapse.
The 930-ton span fell onto the roadway as motorists were waiting under the bridge at a stoplight. Six people were killed, including one construction worker. Another worker was permanently disabled.
The OSHA report is the first time federal investigators have stated unequivocally that the roadway should have been closed in response to the cracking on the bridge, one of the principal points of public concern after the catastrophic accident.
The report also dings FIU and the Florida Department of Transportation, which oversaw the project but did not have direct involvement in design or construction, for not stepping in and demanding that FIGG’s conclusions on the morning of the collapse be reviewed by independent experts — something they had the ability to do, according to OSHA. Both had representatives at the meeting.
FIU declined to comment, citing an open investigation by the National Transportation Safety Board. That agency’s report into the cause of the collapse is expected later this year.
The document also confirms what independent experts who examined the bridge design plans and engineering calculations for the Miami Herald have hypothesized: that the collapse was triggered by FIGG’s sending work crews to re-tension internal support cables at the critical structural connection where the cracks appeared, and that the task was a misguided effort to close the widening gaps. That, OSHA concluded, was a fatal error. The re-tensioning further weakened a structural joint at the north end of the span that was already severely overstressed and failing because of a design error by FIGG that made it too weak to hold up the bridge. The additional stress caused by the re-tensioning led to the collapse, OSHA concluded.
“FIU, FDOT and MCM did not insist that all computations performed by FIGG, including FIGG’s recommendation to re-tension the PT bars, be peer reviewed. They deferred to FIGG’s conclusions, and failed to apply their own judgment and judiciousness, even though FDOT, BPA and MCM have extensive experience in bridge and concrete construction,” OSHA said in its report.
Louis Berger, and BAP did not immediately respond to requests for comment. In a statement released Tuesday night, FIGG called the OSHA report “factually inaccurate and incomplete.” It also said the report included “flawed analyses” and did not “Include an evaluation of many important factors pertinent to the construction process leading up to the accident.”
FIGG comes in for an unusually blunt thrashing by OSHA. The agency’s investigators conclude that FIGG and its chief design engineer, W. Denney Pate, failed to design the bridge properly, then compounded the error by not raising an issue over an inadequate review by Louis Berger of that design. FIGG also failed to take the growing cracks seriously enough to investigate their cause or seek a second, independent opinion on whether they represented a safety hazard, OSHA said.
But the report notes that Pate and his team were sufficiently concerned to ask MCM to hurry up construction of the bridge’s back end, a connector leading from the cracking north end of the completed span to Sweetwater. That back span would have provided sufficient additional structural strength to support the failing connection, the independent experts consulted by the Herald said.
The report also zeroes in on what it says were consequential lapses by Louis Berger, hired to conduct an independent review of FIGG’s design. Because of a “constrained” budget and timetable, the sole unnamed engineer assigned by the firm to the review was not asked to conduct the sort of detailed analysis that would have caught the design errors and prevented the bridge’s collapse, OSHA concluded. Berger was supposed to have reviewed plans for the intermediate stage of construction after the bridge was lifted into place — the point at which it collapsed — but did not, OSHA said.
“The entire review was conducted by one engineer without any assistance from others at Louis Berger. It is interesting to note that neither FIGG, FIU nor FDOT raised the issue of why the structural design of the intermediate stage was not checked by Louis Berger,” OSHA wrote.
The report notes that FIU and FDOT may not have known that Louis Berger did not review the intermediate stages of construction. But it adds that FIGG should have known.
OSHA said Louis Berger did not respond to its repeated request for copies of its review documents and emails between the firm and FIGG, but the agency was able to speak to the engineer who worked on the review because he had left the firm for unrelated reasons.
“If Louis Berger had checked the design at Stage 3, it could have discovered structural deficiencies in the design, and this incident could have been prevented,” the report says. “An opportunity was missed.”
Stuart Grossman, an attorney for survivors Kevin Hanson and Richard Humble, said Tuesday that he found the conclusions in OSHA’s report “appalling” in their detail and scope.
“This case is a lot worse than I thought it was in the beginning. All involved let the public down. And the final error in not shutting down the roadway continues to shock me, and even more so now,” Grossman said.
He said he found sections touching on Louis Berger’s role especially troubling because he said the firm’s attorneys have insisted it had no role in the collapse.
“It lays to waste one of their chief defenses,” Grossman added. “Louis Berger has been hiding in ways that are unconscionable. This reveals Louis Berger not only let FIGG down, but it also failed to provide peer-review documents to the government. It’s unbelievable. They were never on the damn job. They never did what they were supposed to do.”
The OSHA report confirms an indication contained in a summary of the meeting, released last month, that FIGG concluded the cracks did not present a safety concern even though its engineers did not know what caused them — and despite clear evidence that they were growing daily. The report contains a series of emails and texts from construction crew members expressing alarm to superiors over the size and appearance of the cracks.
The engineers should have known the bridge needed to be shored up immediately “until final evaluations were done and remedial measures implemented,” the report says.
Construction workers began expressing concerns about cracking soon after the span was lifted into place over the road on March 10, the report shows. That day, Kevin Hanson, supervisor of a crew tasked with adjusting the tension of structural support elements of the bridge after the installation, sent a text message reporting cracks that had him “visibly disturbed,” according to accounts provided to OSHA.
“It cracked like hell,” he wrote in a text message accompanying a photo of the cracks. The text went to his boss at tensioning subcontractor VSL, Sam Nunez. The OSHA report describes Hanson as “one of the most knowledgeable (post-tensioning) field personnel in South Florida.” Hanson, who was working atop the span’s canopy when it fell, was severely injured.
Two days later, on March 12, at least one MCM employee expressed worry about the cracks photographed earlier by a “disturbed” crew member of a subcontractor.
Shortly before 5 p.m., Rodrigo Isaza, MCM’s senior project manager, sent an email to engineers with FIGG. The email contained photos of cracks at the bridge and a tone that OSHA described as a “sense of urgency.”
Isaza wrote “some of these cracks are rather large and/or of concern…your immediate attention and response is required.” But as late as the morning of the collapse, FIGG showed no sign of a sense of urgency and no concern over safety, the report indicates.
FIGG appeared to downplay the cracks, OSHA said, insisting in an interview with investigators that they had not been expanding once the span, built by the side of the road, was lifted into place.
“In fact, the cracks were expanding every day. In the meeting on the morning of the collapse, BPA informed MCM that the cracks were expanding in length, as recorded by BPA in the minutes from the meeting on March 15, 2018,” OSHA wrote.
In fact, the report notes, the cracks were several inches deep. Under FDOT specifications, cracks deeper than half an inch are classified as significant structural cracks, OSHA noted. Pate and other FIGG engineers inspected the cracks in person on the morning of the collapse.
“FIGG should have also noticed that the cracks were getting longer, wider and deeper compared to the pictures of the cracks they had seen earlier,” the OSHA report says.
The report also takes aim at the sole FDOT representative at the meeting, a civil and mechanical engineer named Alfredo Reyna, for failing to challenge FIGG. Reyna was not an FDOT employee, but a consultant for the agency on the project.
“Mr. Reyna was …. fully aware that FIGG did not know why the cracks were taking place, and still FIGG claimed that the bridge structure had no safety issues,” OSHA’s investigators wrote. “Mr. Reyna also knew that the re-tensioning of the diagonal PT bars [was] taking place in the afternoon, the same day. As a licensed professional engineer, it is reasonable to expect that Mr. Reyna would recommend to MCM and FIU to hold all work, including re-tensioning of the PT bars, until the measures recommended by FIGG were reviewed by FDOT’s structural group in Tallahassee, and FIGG determined the cause of the cracks.
“Mr. Reyna did call the Tallahassee structural group soon after the meeting was over but the person he called was not available.”
The report also raises questions about FIGG’s design. It concludes that a critical connection point at the span’s north end where a diagonal support piece met the pedestrian deck was too weak to resist the diagonal “shearing” forces placed on it once the bridge was suspended in place over a pair of pylons, one at each end. The cracks, which appeared almost immediately, should have been a warning sign, OSHA wrote.
The cracking should have been especially concerning to FIGG because of another questionable design decision, OSHA suggested. The bridge was an unorthodox variation on a standard “truss” design, in which a lattice of steel support pieces runs along each side of the span to provide structural strength. That sort of design is known as a “redundant” design because failure of a single piece won’t lead to collapse.
But FIGG’s design for FIU boasted only a single line of trusses running along the center, meaning failure of any one element could cause the bridge to fall, OSHA said. That design, selected by a committee picked by FIU, contravened a recommendation by the school’s planning consultant, TY Lin International, which recommended the university select only a “redundant” design to ensure safety, OSHA said.
“The selection committee was swayed by the graphics and rendering of the bridge and did not consider the non-redundancy of the structure,” the report states.
In September, OSHA cited five companies for seven worker-safety violations in the bridge collapse, fining them a total of $86,658 in proposed penalties. The companies included FIGG, MCM and Bolton Perez & Associates.
On May 22, a federal bankruptcy judge in Miami presiding over MCM’s post-collapse bankruptcy approved a $42 million insurance settlement for victims of the bridge failure or their survivors. FIU also gave up its claim to a $5 million insurance payout, with the requirement that it also go to the victims.