Engineered to support a mammoth 1,661-foot main span, the new Harbor Bridge being built in Corpus Christi will make an impressive addition to the bay area between the counties of San Patricio and Nueces. The main span of the future regional icon is destined to become the longest cable-stayed, concrete segmental bridge in the United States and Canada – and the tallest structure in South Texas.
The $802.9 million U.S. 181 Harbor Bridge Project began construction in August 2016 and is part of the Texas Department of Transportation’s (TxDOT) long-term plan to improve safety for motorists by addressing structural deficiencies and navigational restrictions of the current bridge. It is also intended to bolster regional economic opportunities.
The design-build venture led by Flatiron-Dragados, LLC consists of building a six-lane, cable-stay, concrete-segmental bridge with a 170-year service life. Crews are also reconstructing portions of U.S. 181, Interstate 37 and the Crosstown Expressway. The five-year undertaking encompassing 6.44 miles’ worth of bridges and connecting roadway will conclude with the demolition of the existing Harbor Bridge in 2021.
Low Clearance, High Safety Incidents
Back in 2003, a TxDOT feasibility study concluded that U.S. 181 and the Harbor Bridge needed to be improved to maintain a safe, efficient transportation corridor. The existing span with 138 feet of navigational clearance crosses the 47-foot-deep Corpus Christi Ship Channel.
Open since 1959, the current bridge handles nearly 62,000 vehicles daily and has multiple safety issues due to lack of shoulders, steep grade and reverse curve. This connector also has an accident rate higher than the statewide average.
While the through arch bridge met design standards when it was built six decades ago, it is too low for many of today’s larger ships – making it difficult for the Port of Corpus Christi to compete with other Gulf Coast deepwater ports. Furthermore, the aging structure is costly to maintain and has no acceptable access for pedestrians or bicyclists.
A Unique Design
The new bridge design incorporates several unique aesthetic features including a community plaza, nighttime LED lighting and xeriscape landscaping. Folks can also enjoy spectacular views of Corpus Christi’s eastern coastline from a belvedere on the structure’s shared-use path.
Rising to a height of 538 feet at the peak of each support pylon, the superstructure will have an above-waterline clearance of 205 feet and a horizontal clearance of 514 feet. Workers will construct three 12-foot lanes in each direction with a median barrier, 10-foot shoulders and a 10-foot shared-use bicycle/pedestrian path extending along the length of the main span and approach viaducts. The bridge’s torsionally-rigid shapes will serve to reduce the amount of structural displacement and stresses.
Crews have already produced over 600 of the 2,600 pre-cast concrete bridge segments needed for this project. Approach and main-span segments are roughly 10 feet tall and 14 feet tall, respectively. Each bridge deck segment varies in width depending on the direction of travel: 58 feet wide for southbound lanes and 69 feet wide for northbound lanes. Eight specialty molds shipped from Italy are being used to form the 100-ton box girder pieces.
“The concrete in these modular segments typically take 14 hours to cure and achieve 2,500 psi compressive strength,” says Project Engineer Nick Manfredini. The custom-designed, low-permeable concrete mixes consisting of aggregate, sand, cement, fly ash, slag and a corrosion inhibitor are being used to promote high compressive strength and long-term durability.
To hoist the approach viaduct segments into place, the project team commissioned an enormous launching gantry crane, which was erected at the end of October. The oversized lifting system was shipped in pieces from manufacturing facilities in Italy and China directly to the project site, where construction workers assembled the support beams, two box girders, the front and rear truss structures, and the winch gantry.
“The main span segments will be placed by derrick cranes on the main span deck. The precast box girder sections of deck will be epoxied together and post-tensioned in sections. These sections will be supported by cable stays extended down from either side of the pylons,” explains Deputy Project Manager John Palmer. “This erection process will begin next to the pylons where the cable stays will be shortest and progressively move outward where the cables stays will be the longest.”
The two 538-foot-tall pylons, he adds, will be supported by footings measuring 132 feet by 72 feet by 18 feet. “These massive footing will be made up of 6,336 cubic yards of concrete each and will be founded by 20 drilled shaft caissons. These shafts have been completed using large augers boring down approximately 200 feet for each 10-foot-diameter shaft,” says Manfredini.
Connecting Construction to the Classroom
This past summer, a group of local teachers volunteered their time off to experience the Harbor Bridge Project firsthand, as part of the state’s new Texas Teacher Externships Program (TEX2). Sponsored by the Texas Education Agency, TEX2 enables educators to learn from and collaborate with experts in a wide range of professions and industries.
Back in January, the Education Service Center-Region II reached out to Harbor Bridge team members to see if they would be willing to host teachers from the externship program, which is focused on STEM (science, technology, engineering and math) education. TEX2 does more than strengthen instructors’ STEM knowledge and skills – it helps them integrate real-world understandings of industry and business into their teaching practices.
“Historic projects like this don’t just happen every day, which was our whole basis for choosing to participate,” says Lorette Williams, Public Information Coordinator for the Harbor Bridge Project. “It is important for local educators to fully understand the scope and magnitude of such projects, so they can share their experiences with students in hopes of igniting an interest in a monumental project like this one.”
A total of 10 educators spent a week in July meeting with project managers, engineers, designers and construction workers, both in the field and in a classroom-type setting. They even visited the Pre-Cast Yard in Robstown, Texas, where workers demonstrated the entire cycle of constructing a concrete bridge segment and how to move these pieces using a straddle carrier.
Amanda Edmonds, a Career and Technical Education (CTE) teacher from Gregory-Portland ISD, visited four sites during her two-week externship – including the Harbor Bridge Project, which she says has positively altered her perceptions about construction and its impact on communities. What’s more, she learned about a host of architecture, engineering and construction (AEC) career paths that she could share with her students.
“The Harbor Bridge Project team brought out some of their essential personnel. We got to meet the project manager and others – people from the very top all the way to individual construction workers,” Edmonds shares. “Everybody was extremely open and willing to tell us about what they do, why it’s important, what training and backgrounds they have. They were willing to answer any of our questions.”
She adds, “We as teachers, we teach. Going out into the AEC industry gives us the advantage of knowing how to teach our students ways to succeed in these types of career fields. When I talk to my students, I’m now able to share with them the soft, medium and hard skills used in various positions. Regardless of whether they want to be welders, or managers, or human resource personnel – these new insights apply across the board to every single student.”
Edmonds spoke at length about the various project areas she visited, sharing how this element of the externship bolstered her appreciation for the extensive construction activities being performed. “Watching what’s taking place in the field helped me to better understand the scope and sequence of what is being done in our community, which is phenomenal,” she adds.
The Harbor Bridge team is obviously focused on more than simply upgrading infrastructure. They’re also dedicated to transforming people’s perceptions about the building and construction industry.
Williams concludes, “I think the entire experience was extremely eye-opening and valuable to teachers. Many times we talk about the importance of building this brand-new bridge. But sometimes you have to peel back the layers of the project – to understand what is being built and how it will impact the community – before you can come to appreciate the uniqueness of this great effort.”
· Owner: Texas Department of Transportation
· Design-Build Contractor: Flatiron-Dragados, LLC, a joint venture of Flatiron Construction Corp. and Dragados USA
· Cost: $802.9 million
· Project Delivery Method: Design-Build
· Construction Start: Summer 2016
· Estimated Substantial Completion: Spring 2021
Did You Know?
Construction workers are utilizing astronomical amounts of materials to complete this massive bridge replacement project. Here are some projected estimates:
· 168 concrete pier segments
· 2,600 concrete segments for cable-stayed bridge
· 22,500 tons of rebar
· 221,000 square feet of MSE walls
· 300,000 cubic yards of concrete
· 1.3 million cubic yards of earthwork
· 8 million linear feet of strand for the cable-stayed system
· 12 million linear feet of post tension cables
All photos courtesy of the Harbor Bridge Project
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