Dive Brief:
- In the latest update on its investigation into the deadly March 15, 2018, collapse of the Florida International University pedestrian bridge in Miami, the National Transportation Safety Board has pointed to errors in design as a factor. The report is preliminary, and investigators did not name these flaws as the cause of the bridge failure.
- As part of the NTSB investigation, experts from the Federal Highway Administration evaluated the 174-foot span's design and construction, which was underway at the time of the collapse, and found flaws in the design of "the northernmost nodal region," where two truss members were connected to the bridge deck. The NTSB reported that as a consequence of the design errors, there was an overestimation of the capacity of an important section made up of diagonal and vertical members and a seeming underestimation of the load to which that section would be subjected. Investigators also determined that the cracks observed in this same area prior to the collapse are "consistent with the identified errors."
- In addition, experts at the highway administration's Turner-Fairbank Highway Research Center have conducted tests on the concrete and steel used in the construction of the bridge. While testing is still ongoing, initial reports have revealed that concrete samples taken from the bridge deck and canopy thus far have met compression and air content requirements. Tests have also shown that steel reinforcing bar and post-tensioning rod samples have met the minimum yield strength, tensile strength and percent elongation at fracture specifications.
Dive Insight:
The latest update on materials testing is in line with the NTSB's previous report dated Aug. 9, 2018, in which the agency indicated that there seemed to be no sign of flaws in the bridge material. The August report also included an extensive photographic account of cracks at what appears to be the problem area of the bridge — the north end. Photos of cracks at or near diagonal member 11 and vertical member 12 show the development of what were minor cracks before the span's installation. Fissure-like gaps developed where the structure is presumed to have failed.
OSHA, while making no claims as to the cause of the collapse, did note alleged safety violations that day and cited five contractors working on the bridge, including engineer FIGG Bridge Engineers and general contractor Munilla Construction Management. The agency issued FIGG and engineering and inspection company Network Engineering Services one serious violation each with an associated fine of $12,934 for subjecting employees to physical danger by allowing them to work from the bridge after cracks were discovered.
Structural Technologies and Munilla each received two serious violations for failure to provide sufficient personal fall arrest systems. OSHA also issued concrete formwork contractor The Structural Group of South Florida one serious violation and proposed a fine of $9,054 for also failing to provide an adequate personal fall arrest system. All five companies have contested the violations (here, here, here, here and here).
