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Local engineer helps understand proposed changes to new Harbor Bridge

Dissecting the preliminary changes to the new Harbor Bridge
Posted at 10:02 PM, Sep 06, 2022
and last updated 2022-09-06 23:20:08-04

CORPUS CHRISTI, Texas — Our latest update with the new Harbor Bridge was that the contractor, Flatiron/Dragados had responded to Texas Department of Transportation's (TxDOT) ultimatum. With that, Flatiron has pitched some ideas on how to address TxDOT's safety concerns. To help us understand what is being proposed, we reached out to a civil engineering professor at Texas A&M University Kingsville.

“I think this is great progress,” Dr. Francisco Aguiniga said.

Aguiniga helped break down what the initial safety concerns were.

Those came from an independent third party review by International Bridge Technologies.

First issue was, within the two main towers of the bridge, there is too much tension on the drill shafts, the support that goes underground.

What’s been proposed is extending the foundation out. They would also add more, seven smaller drill shafts. The original drill shafts in place are 10 feet in diameter.

Flatiron/Dragados said that first solution will solve the second issue, problems with the foundation cap. By extending the foundation of the towers, they can add longer support extensions so they won’t slip out.

“We want to make sure all of those bars fail before they pull out of the concrete," Aguiniga said. "So, that was one of the recommendations that some of those bars were not deep enough.”

This idea would decrease the chance of failure, but if it did fail, it wouldn't be because those bars accidentally slipped out of place.

The third concern was to address that more compression was needed around the delta frames and the precast boxes, where the roadway and columns will meet. More reinforced bars have been proposed, but then would need to be filled in.

“There’s different options to anchor things, they mention here epoxy. Other options are to use grouting material,” said Aguiniga. "Epoxy is a plastic, grout is a sedimentation material."

The fourth issue was preventing the possibility of uplift or the contortion of the bridge. Three remedies were given.

Increase the size of the cable anchors.

Add a steel beam beneath the road portion. A good way to think about it is think of how a splint prevents your finger from bending.

The third option involves a redesign to prevent bearing decompression. It includes modifying the temporary pier diaphragm, bearings and superstructure.

“That would include partial demolition of those diaphragms because they’ve already been put together,” Aguiniga said reviewing the documents.

The fifth issue was problems caused by crane placement during the project. For now, Flatiron proposes making minor adjustments, but just monitoring the situation.

"If everything is double and triple checked, it's looking good. Should be easier to resume construction," said Aguiniga.

He believes these ideas are viable if they meet the specifications up to TxDOT's liking.

“Perhaps they might work," he said. "But what I was seeing in the report there are more issues, these are the bigger ones."

Aguininga noted there are 22 issues pointed out in the IBT review. It's unclear if addressing these five issues will correct all concerns.

These proposed ideas are all preliminary. TxDOT said they are in constant talks with the engineer and IBT to decide on solutions.

TxDOT has not removed the notice of default given to the contractor. It will stay in place until they have in writing that Flatiron/Dragados is committed to correcting the project.

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