by: Tom Regan Updated:
ATLANTA,None - An independent investigation has found defective
epoxy, or industrial strength glue, on anchor bolts caused a large canopy fence to collapse from the 17th Street Bridge last summer.
The one-ton steel and aluminum structure broke free from a bridge wall and crashed onto the downtown connector in midtown Atlanta the night of Aug. 13, 2011. No one was injured.
The Georgia DOT hired forensic engineering firm Wiss, Janney, Elstner & Associates to investigate the reason for the collapse.
Friday, the firm released the
findings of its study and concluded epoxy that was used to adhere bolts from the fence to the bridge weakened and failed.
"The primary cause of the canopy failure relates to epoxy anchor adhesive, the disproportionate mixing of adhesive compounds, and inclusions or trapping of air voids in anchor holes," forensic engineer Mark Moore said.
Moore also said the epoxy was poorly mixed and applied to anchor holes. He said the same material was used in a large tunnel project in Boston where a concrete ceiling tile fell, killing a motorist.
"The poor performance of the epoxy anchors was similar to that which was observed by the NTSB on the collapse of ceiling panels in the I-90 tunnel in Boston in 2006.
The canopy fence was erected in 2004.
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Following the accident in Boston, the Georgia Department of Transportation said it inspected anchor bolts on the 17th Street Bridge but detected no observable signs of failure.
Channel 2's Tom Regan asked the state's chief engineer who was to blame for the fence toppling onto the highway.
"Accountability goes to all of us who were involved. From the construction contractor who put in the adhesive, to the department (G-DOT) who was responsible for acceptance and inspection of a quality product," GDOT Chief Engineer Gerald Ross said.
Ross said the state will no longer use epoxy for attaching heavy structures to bridges and overpasses.
He also said the state is now reviewing structures on thousands of bridges to make sure they are safe and secure.