Samples of rebar recovered from the collapsed pedestrian bridge, await transport to the Federal Highway Administration’s Turner-Fairbanks Highway Research Center, where the samples underwent materials testing as part of the NTSB’s ongoing investigation of the March 15, 2018, fatal, bridge collapse. NTSB photo by Adrienne Lamm

Federal investigators said that errors were made in the design of a 174-foot pedestrian bridge at Florida International University, and that cracking observed before the bridge's collapse was consistent with those errors.

Six people died and eight others were injured when the bridge collapsed March 15, 2018. Eight vehicles were crushed in the collapse, seven of the vehicles were occupied.

The update from the National Transportation Safety Board (NTSB) stated that errors were made in the design of the northernmost nodal region of the span where two truss members were connected to the bridge deck.

The design errors resulted in an overestimation of the capacity (resistance) of a critical section through the node, and an apparent underestimation of the demand (load) on that section.

The design review was conducted by the Federal Highway Administration’s Office of Bridges and Structures in support of the NTSB’s ongoing investigation. The Federal Highway Administration is a party to the NTSB’s investigation.

(Read "Bridge Cracks Were Found Earlier Than First Reported: Miami Herald.")

The Turner-Fairbanks Highway Research Center, part of the Federal Highway Administration, conducted tests and examinations of concrete and steel samples taken from the bridge following its collapse. The concrete and steel specimens reportedly met the project’s build plans specified minimum requirements.

The NTSB said that findings from the materials tests included:

• Concrete core specimens from the bridge deck and bridge canopy met the compression requirements in the project plans.
• The design plans specified that concrete used for the project had to be in accordance with Florida Department of Transportation specifications. All specimens from the bridge deck and bridge canopy were within the specified range for total air content.
• Tension test results of size #5, #8 and #11 steel reinforcing bars revealed that all met minimum yield and tensile strengths and percent elongation at fracture, for their respective sizes. Size #7 bars could not be tested due to collapse-induced deformation.

The NTSB said that its investigation of the bridge collapse is ongoing and that the information in its update is preliminary and will be supplemented or corrected as the investigation moves forward.

In September, the U.S. Department of Labor’s Occupational Safety and Health Administration (OSHA) cited multiple contractors for safety violations after one employee suffered fatal injuries and five other employees sustained serious injuries related to the collapse. The five companies collectively received seven violations, totaling $86,658 in proposed penalties.