The National Transportation Safety Board released a preliminary report on the agency's ongoing investigation of the pedestrian bridge collapse that took place at Florida International Univerisity (FIU) on March 15 in the city of Sweetwater.
According to the report, the 174-ft-long bridge fell about 18.5 ft onto SW 8th Street, crushing or partially crushing eight vehicles that were stopped below the structure at the time of its collapse. As a result of the collapse, one bridge worker and five vehicle occupants died, while four bridge workers and four other people were injured.
The report notes that on March 10—five days before the collapse—the walkway, diagonals and canopy comprising the bridge was moved from the lot, using transporters, into position across the roadway and then lowered onto the bridge piers on either side of the road. On that same day, per the bridge design plans, construction crew members were de-tensioning the bridge diagonal members on the north and south ends of the structure. When the collapse occurred on the 15th, a crew was on the structure to work on retensioning the number 11 diagonal member connecting the canopy and the deck at the north end of the bridge. Since a crane was used for the March 15 work, two of the three westbound lanes below the north end of the bridge were closed to traffic, but the five eastbound lanes remained open.
The NTSB says they are continuing to evaluate the bridge design, construction process and materials, as well as evaluating cracking in the areas of diagonal members 2 and 11. The report says that photographic documentation from Feb. 24 depicted cracking around diagonal 11. The agency is conducting additional forensic examination of several bridge structural components and destructive testing of multiple core and steel samples. The collapse is still under investigation as the NTSB determines the probable cause, with the intention to issue safety recommendations for future work.