HOUSTON – An independent review of the design of a bridge being built across the Houston Ship Channel on Sam Houston Tollway is underway. The review follows a national report chiefly blaming the bridge’s designer for a fatal bridge collapse near Miami, officials in Harris County said Thursday.
Six people died after a pedestrian bridge collapsed at Florida International University in March 2018. The National Transportation Safety Board in October ruled the bridge’s designer, FIGG Bridge Group, was chiefly responsible for the collapse due to flaws in design and calculation. FIGG also designed the ship channel bridge.
Portions of the abstract of the NTSB report read, in part:
“...the design team underestimated the demand (loads imposed on structural members) that would be acting on the nodal area. The investigation compared postcollapse calculations for the demands on the node with the design calculations. This comparison found that the demand for the node was nearly twice what the design team had calculated."
“Second, the design team also overestimated the capacity of the node to resist shear (horizontal force) where the nodal region (11/12) was connected to the bridge deck. This overestimation was the result of the designer using incorrect loads and load factors in its calculations. These two design errors resulted in a node that lacked the capacity to resist the shear force pushing the node to the end of the bridge.”
The Harris County Toll Road Authority owns the bridge that is being built over the Ship Channel and hired FIGG, which beat out seven other firms for the job. The collapse in Florida occurred after HCTRA hired FIGG.
HCTRA officials said Thursday FIGG’s prior track record and qualifications won the company the bid for design.
“Partly because they had done seven bridges very similar to ours, out of 13 that are in the United States, and they were very qualified from that aspect,” said John Tyler, deputy director of engineering for HCTRA.
Following the collapse in Miami, the Harris County Commissioners Court in March approved a $3.9 million contract with COWI North America, Inc. COWI is an independent engineering consultant hired to review FIGG’s design of the ship channel bridge. While a final report is not expected to be complete until the spring, officials said the firm has conducted a preliminary review of the bridge’s foundation.
“The preliminary finding was that everything is fine and so we’re moving forward and that was our initial first look at it was we need to find out of what we were constructing at the time was gonna be successful,” Tyler said.
HCTRA officials believe the bridge will be safe based on that preliminary report, as well as the system by which the agency selects designers and builders: a design-bid-build system, officials said, creates additional oversight.
TxDOT suspends design work on Corpus Christi bridge
Following the NTSB’s final report on the FIU bridge collapse, the Texas Department of Transportation suspended design activities of the Harbor Bridge project in Corpus Christi.
“Safety is always TxDOT’s top priority and we have been closely reviewing the design and construction activities since the inception of this project,” the agency said in a statement.
Just like the Ship Channel bridge, the Harbor Bridge will be cable-stayed. The process is similar to the one used on the Fred Hartman Bridge in Baytown.
So, if TxDOT suspended design in Corpus Christi should HCTRA do the same?
“Do we feel like it was necessary? Not based upon FIGG’s record prior to this building 7 of 13 structures like this around the United States,” Tyler said.
Officials say bridge will improve traffic flow
The current Ship Channel bridge, which opened to traffic in 1982, carries approximately 55,000 vehicles a day, according to HCTRA. That number is expected to grow to about 160,000 vehicles a day by 2035, according to the agency.
The twin span bridge will widen the road by four lanes in each direction, upon completion in 2024. It will also add shoulders to the side of the road.
Phase one, the southbound side, is currently under construction. It is expected to be completed in 2021. From there, the current bridge will be demolished and construction on the northbound side will begin. It’s set for completion in 2024, officials said.
The overall Ship Channel Bridge Replacement Program cost is $962 million, officials said. That number includes construction, design, right of way, utilities, construction management, inspection and materials testing.