Designers overestimated load capacity of critical FIU
pedestrian bridge section: NTSB update report
Florida Construction News staff writer
The National Transportation Safety Board (NTSB)
says in an investigative update about the fatal Florida In-
ternational University (FIU) pedestrian bridge collapse in
Miami that errors were made in the design of the 174-
foot span, and that cracking observed before the col-
lapse is consistent with those errors.
Six people died and eight others were injured when
the bridge collapsed on March 15, 2018. Eight vehicles
were crushed in the collapse, and seven of the vehicles
were occupied, the NTSB says in its mid-November up-
date. Munilla Construction Management built the struc-
ture based on designs from FIGG Bridge Group (FIGG).
Two days before the collapse, a FIGG engineer left a
voicemail for Florida Department of Transportation
(DOT) officials to report cracking had been found at one
end of the concrete span, but the company did not
think it was an issue, the Associated Press has re-
ported. State officials did not hear the voicemail until after
the collapse. University officials said DOT officials had
been included in a meeting to discuss the cracking
hours before the collapse.
The NTSB update states errors made were in the de-
sign of the northernmost nodal region of the span
where two truss members were connected to the
bridge deck. The design errors resulted in an overesti-
mation 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 Struc-
tures in support of the NTSB’s ongoing investigation.
The Federal Highway Administration is a party to the
NTSB’s investigation.
The Turner-Fairbanks Highway Research Center, part
of the Federal Highway Administration, conducted nu-
merous tests and examinations of concrete and steel
samples taken from the bridge following its collapse.
The concrete and steel specimens tested by Turner-Fair-
banks Highway Research Center personnel met the pro-
ject’s build plans specified minimum requirements.
Findings from the materials tests include:
• Concrete core specimens from the bridge deck and
bridge canopy met the compression requirements in
the project plans;
• The design plans specified concrete used for the
project had to be in accordance with Florida Depart-
ment of Transportation specifications. All specimens
4 – DECEMBER 2018 - JANAURY 2019 — Florida Construction News
Samples of rebar recovered from the collapsed FIU pedes-
trian bridge, await transport to the Federal Highway Ad-
ministration’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)
from the bridge deck and bridge canopy were within
the specified range for total air content; and
• Tension test results of size #5, #8 and #11 steel re-
inforcing bars revealed 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’s investigation of the bridge collapse is on-
going and the information contained in the investigative
update is preliminary and will be supplemented or cor-
rected as the investigation progresses. As such, no con-
clusions about probable cause should be drawn from
the information contained in the investigative update,
the agency says.
The investigative update is available online at
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