The National Transportation Safety Board (NTSB) this week released an investigative update on the collapse of the Florida International University (FIU) pedestrian bridge in Sweetwater, Fla., revealing significant errors made in the design of the bridge that collapsed and killed six people back in March.
Since the first NTSB investigative update was issued back in August, new information has developed on the bridge design, and additional forensic examination and evaluation of the structural bridge components has been completed. The August update revealed large cracking that appeared in the section of the span that was believed to have failed when the structure collapsed.
In their most recent update, the NTSB disclosed that the FHWA Office of Bridges and Structures are supporting the investigation by providing resources to evaluate the bridge design and construction. The FHWA evaluations included an assessment of the available design calculations and construction plans to determine if they were done in conformance to the appropriate design and constructions specifications.
The NTSB report says that though the evaluation is ongoing, the assessment has determined that errors were made in the design of the northernmost nodal region of the 174-ft-long span, where two truss members were connected to the bridge deck. The report determines that the design errors resulted in the overestimation of the capacity of a critical section through the node comprised of diagonal member 11 and vertical member 12, and apparent underestimation of the demand on that same critical section. What's more, the evaluation determined that the cracking observed in the node prior to the collapse is consistent with the identified errors.
FIU released a statement after the release of the NTSB investigative update. “At FIU, we continue to fully cooperate with the NTSB so that it may finish its investigation and complete a final report and safety recommendations," Kenneth Jessell, senior vice president for finance and administration and chief financial officer at FIU, said in the statement. "We hope the results of the investigation will help bring closure to the families and loved ones of the victims.”