The reason for girder cracks on the elevated section of U.S. 90 over Bayou Ramos remains under investigation, but engineers have determined that the concrete used to pour those sections was good.
Core samples from the damaged sections revealed no irregularities, according to state Department of Transportation and Development District 3 Engineer Administrator Bill Olivier.
“We still are not sure of what the causes are,” Olivier said, adding that engineers may never know the reason unless the girders — located between the substructure where they hold up the decks cars drive on — are destroyed and studied.
Olivier called the cracks “unexpected” in a bridge of this age. It opened July 20, 1999, but this particular section was constructed in 1994. He noted that this problem is unique in the state, but may not be in the nation.
Because he has not seen the cracks himself, Olivier could not describe the amount or size of the cracks, but said they are “a little more than hairline.”
When asked if this could be a problem for the rest of the elevated sections of U.S. 90, he said it is unlikely because while they may look the same, “most are pretty unique. They are not all the same.” Only one other section is constructed in the same manner, and it was checked for cracks but found not to have any, Olivier said.
The cracks were discovered while the DOTD was conducting a routine inspection in March. The bridge’s load limit was reduced shortly thereafter with truck traffic weighing greater than 15-25 tons being detoured to guarantee that no further damage will occur to the structure.
Olivier said the main focus now is on repairing the structure so it can continue in service.
Phase I of a rehabilitation project to begin repairs to the bridge is scheduled to begin in August. Work on girders deemed high-priority — those with visible cracks — will be addressed in Phase I. Remaining girders will be addressed in Phase II, which is scheduled to take place in fiscal year 2013-14.
Meanwhile, truck traffic is detouring on La. 182 and Lake Palourde Bypass Road.