Work on a nearly $1 billion bridge near Houston has temporarily stopped so that a potential design flaw can be corrected.

The Harris County Toll Road Authority (HCTRA) said construction on the main pylons of the cable-stayed portion of the Sam Houston Tollway Ship Channel Bridge replacement project will halt for several weeks.

Jump form assembly for the southbound M4 pylon. Source: HCTRALast March, HCTRA hired an independent consultant — COWI North America Inc. — to conduct a complete independent review of the Ship Channel Bridge engineering design performed by FIGG Bridge Engineers Inc.

While COWI’s full project review is expected to be complete by March 2020, it has identified an issue related to the design of the curved portions of the pylon legs for the $962 million bridge. HCTRA said in a statement that "briefly pausing construction will allow for the engineer of record (FIGG) to design a solution, to be reviewed by COWI, and incorporated into construction before the work progresses."

Once FIGG and COWI agree on design changes, work will resume on the pylons.

Florida bridge connection

Last October, the National Transportation Safety Board (NTSB) said that FIGG Bridge Engineers made "significant errors in determining loads" for a pedestrian bridge that collapsed in March 2018 at Florida International University near Miami. In particular, the NTSB said that FIGG chose the wrong interface shear demand value that led to a "severe underestimation" of demand. In addition, the firm chose the wrong load factor in calculating the permanent compression loading, which led to a "significant overestimation" of capacity.

Robert Sumwalt, NTSB chairman, said that public safety oversight was lacking and that the project "should have ensured that a qualified, independent firm provide effective peer review of bridge plans, as required."

Project partners

HCTRA selected FIGG Bridge Engineers as part of a team to execute the bridge replacement project. The firm has served as Engineer of Record on seven of 13 concrete cable-stayed bridges built in the United States.

The project was bid and construction was awarded to Ship Channel Constructors, a joint venture between Traylor Brothers Inc. and Zachry Construction Corp. Their team includes T.Y. Lin International Group to provide construction engineering, a process that verifies a significant component of the overall design. The Texas county selected HNTB to provide construction management for the project.