Cracks in the north and south ends of the pedestrian bridge that collapsed in Miami March 15th are being scrutinized by the National Transportation Safety Board (NTSB) in its ongoing investigation of the incident. One bridge worker and five other people - occupants of crushed cars - were killed when the 174-foot-long bridge fell onto an eight-lane street below. Four bridge workers and four other people were injured.
The bridge was to be completed by early 2019 and was built using an accelerated bridge construction method—a technique intended to minimize disruption of traffic. On March 10, 2018, the walkway, diagonals, and canopy comprising the bridge, which had been built in a lot adjacent to SW 8th Street, was moved from the lot, using transporters, into position across the roadway and then lowered onto bridge piers on either side of the roadway (figure 2). Traffic on SW 8th Street was detoured during the installation period, and the entire roadway was closed to facilitate movement of the structure.
NTSB is evaluating the emergence of cracks in the south and north ends of the bridge and the propagation of cracks in the region of diagonal member 11. Also being examined: the bridge design, the construction process, and the construction materials.
When the collapse occurred on March 15, a construction crew was positioned on the structure working on re-tensioning the number 11 diagonal member connecting the canopy and the deck at the north end of the bridge. Because a crane was being used for this work, two of the three westbound lanes below the north end of the bridge were closed to traffic; however, the five eastbound lanes remained open, and eastbound traffic was not detoured.
In the next month, the NTSB will be conducting additional forensic examination of several bridge structural components and destructive testing of multiple core and steel samples. All aspects of the collapse remain under investigation while the NTSB determines the probable cause, with the intent of issuing safety recommendations to prevent similar events.
Assisting in the NTSB investigation are the following Party Members;
- Federal Highway Administration (FHWA)
- FHWA - Turner Fairbank Highway Research Center (TFHRC
- Occupational Health and Safety Administration (OSHA)
- Department of Transportation Office of the Inspector General (OIG)
- Florida Department of Transportation (FDOT)
- Miami-Dade Police Department (MDPD)
- Florida Highway Patrol (FHP)
- Florida International University (FIU)
- City of Sweetwater (CS)
- FIGG Bridge Engineers, Inc. (FIGG)
- Munilla Construction Management (MCM)
- Structural Technologies, LLC (VSL)
- Barnhart Crane & Rigging (BCR)