NTSB: Update on Miami Pedestrian Bridge Collapse

NTSB at site of Instant Bridge collapse in Miami.
Image: Flickr

The NTSB, from the chairman to the chief investigator of the Miami pedestrian bridge collapse, is adamant in their search for the partially constructed bridge’s failure.

MIAMI — The National Transportation Safety Board (NTSB) issued a statement regarding the focus of its investigation into the March 15th incomplete pedestrian bridge collapse linking the city of Sweetwater, Florida, with Florida International University campus is on measuring and documenting critical structures at the north end of the bridge.

NTSB has confirmed that adjustments to the bridge were being made to two cables at the time of the collapse and related rebar and tensioning are being sent to the Turner Fairbank Highway Research Center, in McLean, Virginia, for testing and evaluation while other bridge components will be examined under NTSB investigation in Florida at a state Department of Transportation location.

NTSB has stressed that it has “not yet determined” if there is any relationship between an undisclosed crack in the concrete of the incomplete bridge, and the tensioning adjustments publicized on Twitter by Senator Marco Rubio and is not speculating on what may have gone wrong.

NTSB outlined significant developments in the investigation:

  • Investigators secured a contract Tuesday to have a company remove components from the bridge that we believe warrant additional examination and testing. These components include sections of the floor, the canopy, a vertical member and a diagonal member; all from the north end of the structure. These components were in the area of where the failure occurred. In addition to these components, we obtained additional core samples from this area to supplement the core samples we obtained earlier.
  • Shipping the core samples along with some recovered rebar and tensioning rods to the Turner Fairbank Highway Research Center, in McLean, Virginia, for testing and evaluation.
  • The investigative team has obtained an exemplar tensioning rod and hydraulic unit used by the construction crew to make tension adjustments to the tensioning rods. These items are also being shipped to the Turner Fairbank Highway Research Center for evaluation and testing.
  • The larger bridge components the investigative team is removing, are being stored at a secured Florida Department of Transportation facility, under the control of the NTSB. The additional examinations and forensic deconstruction of these components will occur there.
  • The investigative team has confirmed that workers were adjusting tension on the two tensioning rods located in the diagonal member at the north end of the span when the bridge collapsed. They had done this same work earlier at the south end, moved to the north side, and had adjusted one rod. They were working on the second rod when the span failed and collapsed.  The roadway was not closed while this work was being performed.

Ongoing work includes:

  • Removal of the post-tensioning device to a temporary storage area and preparing it for shipment.
  • Preliminary comparison of bridge schematics to measurements obtained during the investigators’ examination of the collapsed structure.
  • Interviews with first responders

While segments of the bridge are being transported to and stored at an FDOT facility, there are no plans to reconstruct the bridge as part of the NTSB investigation into why the bridge collapsed. The nature of the structure and the way it failed make reconstruction impractical,” said NTSB.

The NTSB also indicated the next investigation update would be the preliminary report that is prepared following completion of field work, noting that preliminary reports “do not contain analysis and do not address probable cause.”

Watch NTSB Chairman Robert Sumwalt on the independent safety investigation, which government agencies will be involved and how it is being conducted. Joining him on March 16th was Chief NTSB Investigator Robert Accetta. Highlights of the 18-minute press briefing:

  • Accetta said, “It’s not uncommon in other bridge structures for them to put members under tension to strengthen them, it’s not an unusual procedure, but we do need to find out why and what may have caused the failure mechanism. We don’t know yet.”
  • A resolute Sumwalt added some comments about the human tragedy of this collapse:

We don’t want to come back to something like this again.”

Today, NTSB posted to Twitter:

About the author

Andrea Fox

Andrea Fox

Andrea Fox is Editor of EfficientGov.com and Senior Editor at Praetorian Digital. She is based in Massachusetts.