(Credit:Gabriela Collazo)

Experts: Design Changes Like Those Made At FIU Can Lead To Bridge Failure

March 21, 2018 - 10:19 am

MIAMI (1010 WINS/AP) -- We're learning more about what may have contributed to the deadly collapse of a new pedestrian bridge at Florida International University.

Six people died last week when the bridge came crashing down.

The associated press has obtained documents that detail instructions for contractors to move one of the main support structures 11 feet. That widened the gap between supports, and required some new structural design.

The span's signature, 109-foot-tall (33-meter-tall) pylon was to be built atop a base at the span's northern end. It was designed for basic support and to contribute to the aesthetics of the bridge, which was touted as an architectural marvel that would connect the rapidly growing university to the nearby community of Sweetwater. In their winning 2015 proposal, designers said the bridge provided ``spectacular views'' for both pedestrians using the bridge and drivers passing beneath it. They added that the tower could serve as a safety feature because it would have an ``eagle-eyed location'' for additional lighting and security cameras.
Videos of Thursday's collapse show that the concrete, prefabricated segment of the bridge started crumbling on the same end of the span where the tower redesign occurred, two days after an engineer on the project reported cracks in the same location. The segment that failed had been placed atop the pylon's footing, and the taller tower section was to be installed later.
U.S. Transportation Secretary Elaine Chao has ordered her department's inspector general to conduct an audit of the bridge, according to a news release Tuesday from the U.S. Department of Transportation. The agency awarded millions of dollars to the project.
While the NTSB probe has just begun, multiple engineers who reviewed the documents obtained by the AP said moving the tower after the bridge's initial design invited errors.
Henry Petroski, a Duke University civil engineering professor, said even seemingly minor changes in a bridge's design can lead to failures.
 "Once a design is completed, subsequent modifications tend to be suggested and approved without the full care that went into the original design. This has happened time and again in bridges and other engineering structures,'' he said.

Emails among the school, contractors, city officials, and permiting agencies show the project was behind schedule. There were worries that further delays could jeopardize federal funding.

The project was already about $2.6-million over budget.