Illinois Installs State’s First Steel Press-Brake Tub Girder Bridge
Photo Credits: Valmont Structures & Champaign County, Illinois
Watch the project video (above)
In September 2021, Champaign County completed the installation of the first prefabricated steel press-brake tub girder (PBTG) bridge in the state of Illinois. The bridge, manufactured by Valmont, provided a $2.00-per-square-foot savings by using steel instead of an alternative precast-prestressed concrete deck beam structure.
Steel Preferred for Durability and Sustainable Benefits
Champaign County is located in the heart of East Central Illinois, approximately two hours south of Chicago, with a population of 208,861 people and a total area of 1,008square miles. Champaign County is home to the University of Illinois and a leader in education, health care, government, high technology, light industry and agriculture.
Jeff Blue, P.E., County Engineer for Champaign County, and his crew take care of 30 townships, 200 miles of county roads, and about 1,600 miles of township roads.
“We are in the neighborhood of 600 total bridges that we oversee, maintain and specify within Champaign County – that’s a pretty big bridge system,” says Blue.
Blue prefers to use steel for the bridges located within Champaign County. “On the county system, we are almost exclusively selecting steel because we feel that it gives us our best life, and it is going to give us the best fight against salt that we dump on the bridges,” says Blue.
Sustainability is also a factor which Blue considers when selecting the material for a new structure. “Obviously steel is recyclable, so we like the idea of that [feature]. If we tear down a steel bridge, it may be recycled as steel that somebody else uses for one of their bridges,” says Blue.
Relationship with SSSBA Leads to Interest in Steel Press-Brake Tub Girders
In 2021, short span bridge TR-251 in Champaign County needed to be replaced. The existing 57-foot-long bridge was on a township road over a drainage ditch. The backwall, made from wood, was rotting and the deck needed replacement. Rather than try to repair the structure, Champaign County made the decision to replace the entire bridge.
Blue, who is also the current Secretary/Treasurer for the National Association of County Engineers (NACE), had heard about the benefits of PBTG from members of the Short Span Steel Bridge Alliance (SSSBA).
“The SSSBA has a really good relationship with NACE,” says Blue. “At one of our NACE meetings, I had a conversation with some of the SSSBA folks about the idea of a steel press-brake tub girder bridge. This idea fit really well for the TR-251 project.”
Steel Press-Brake Tub Girders Provide Savings Over Concrete Alternative
In 2019, Blue had an initial meeting with SSSBA member Valmont Structures to discuss options for the TR-251 bridge replacement using PBTG (download project plans).
“We bid three or four of the precast-prestressed deck beam bridges in Champaign County this year. The cost for the beams in place for those bridges came in at about $84 per square foot. The PBTG price with the precast deck on top, through a proposal from Valmont, was $82 per square foot,” says Blue.
Based on the overall benefits and cost savings steel provides, Champaign County made the decision to move forward with using PBTG for the replacement bridge project. It would be the first PBTG structure built in the state of Illinois.
Valmont was awarded the project and produced the project-specific superstructure shop drawings and design in accordance with the AASHTO LRFD Bridge Design Specifications and Illinois Department of Transportation (IDOT) “Bridge Manual”.
The shop drawings were stamped by an Illinois structural engineer and reviewed by the engineering firm WHKS. Valmont provided WHKS with a load rating for the bridge superstructure according to the AASHTO “Manual for Bridge Evaluation, Section 6)” and Illinois Department of Transportation Circular Letter 2017-16, “Load Ratings for Local Public Agency Structures” (CL2017-16).
Steel Bridge Produced and Fabricated in the United States
Guy C. Nelson, P.E., Business Development Director of North American Structures for Valmont, provided oversight and management for the sales, design and production of the project.
The bridge was constructed using the Valmont U-Beam, a steel PBTG consisting of AASHTO M270 Grade 50 steel produced and fabricated in the United States. Champaign County acquired the steel plate from steel producer and SSSBA member SSAB Americas located in nearby Montpelier, Iowa.
The Valmont U-BEAM consists of a steel plate formed by cold bending with a press brake. This U-shaped steel plate is then cambered by roll forming to offset any dead load deflections or roadway profile requirements.
Once cambered, bracing angles are welded across the top flanges at specific spacings and steel plate end diagrams are welded at the bearing locations. A single row of shear studs is applied to the top flange by an automated stud welder. These shear studs are spaced for the required fatigue and strength design needs of the project.
“After all of the design and shop drawings were approved, the four steel tub girders were formed with a 60-foot-long press brake from the flat base plate at Valmont’s Valley, Nebraska plate facility,” says Nelson. “Final fabrication—consisting of welded sole plates, angle braced diaphragms, end bearing diaphragms, shear studs and hot-dip galvanizing—were all provided at the Valmont Valley plant.”
Once the steel tub girders were completely fabricated, they were delivered to McCann Concrete Products in Dorsey, Illinois to incorporate the final concrete bridge deck. Per the specifications, the concrete used included a waterproofing admixture called Pavix, which was added as a “salt protection system” to further lengthen the life of the concrete in order to match the long maintenance- free service life of the galvanized steel tub girders.
Steel Girders Installed in One Day
After the bridge units were fabricated, galvanized, and the deck was installed, the four bridge sections were individually transported by standard truck and trailer to the jobsite. Each individual 57-foot-long bridge unit weighed approximately 48,000 pounds.
“So, the nice thing about that is they were within weight limit where they could be hauled on a standard-sized truck, with a standard trailer. They were brought in one at a time, and individually set with a 250-ton crane,” says Nelson.
The four PBTG units, measuring 6 feet 4 inches on the outside and 6 feet on the inside, with the precast decks were delivered to the jobsite, and set and placed in one day. The substructure consisted of a 12-inch metal shelf with 35-foot-long piling driven into a silty clay, to provide a good base for the bridge to sit on. A standard concrete abutment was then poured, with riprap out in front.
“The next day, they came back and did the 8-inch closure pours. So, you are looking at two or three days to set the beams and get the closure pours done,” says Blue.
Steel Provides a 100-Year Service Life
According to Nelson, this project includes a 60-year maintenance-free galvanized coating on the steel beams and a water-repellant treatment/additive in the concrete to lengthen the life of the precast concrete deck. This adds up to a 100-year total bridge service life for an upfront cost that is less than the concrete beam option.
“If I can get 75 to 100 years out of my bridges, I can maybe get a little bit ahead of the curve in the next few years where we will actually have enough money to replace our bridges on a consistent basis in a consistent rotation,” says Blue.
“I am always up for a new challenge and new ideas, and I try to bring those into Champaign County. Hopefully, this will be a kickoff for more PBTG bridges in the state of Illinois,” concludes Blue.
Contact Information
Steel Producer/Mill
David Stoddard
Senior Applications Engineer
SSAB Americas – Montpelier
1770 Bill Sharp Blvd.
Montpelier Steel Operations
Muscatine, Iowa 52761
Tel: 563.381.5759
Email: david.stoddard@ssab.com
Website: https://www.ssab.com/
Steel Fabricator
Guy Nelson, P.E., S.E.
Business Development Director – North American Structures
Valmont Industries, Inc.
28800 Ida Street
Valley, NE 68064
Tel: 616.813.8514
Email: Guy.Nelson@valmont.com
Website: https://www.valmontstructures.com/products-solutions/traffic-mass-transit/bridge-systems
Bridge Owner
Jeff Blue, P.E.
County Engineer
Champaign County Highway Department
1605 E. Main St.
Urbana, IL 61802
Tel: 217.384.3800
Email: jblue@co.champaign.il.us
Website: https://www.co.champaign.il.us/highway/highway.php
What are Press Brake Tub Girders?
Press-brake-formed tub girder (PBTG) is a new technology for short span bridge applications. It consists of modular galvanized shallow trapezoidal boxes fabricated from cold-bent structural steel plate (watch fabrication video). A concrete deck is recommended to be precast on the girder and the modular unit can be shipped by truck to the bridge site.
The system utilizes standard plate widths (based on availability) and is optimized to achieve maximum structural capacity, with most of the steel in the bottom flange and increased torsional stiffness. It is a closed system, since the girder is closed at the bottom. It is versatile for multiple-deck options.
The system utilizes Accelerated Bridge Construction practices, since it:
- Can be installed in one or two days
- Is modular, allowing the use of a precast deck
- Is cost-effective―as much as 1/3 less than a standard concrete girder structure
- Is simple to fabricate, requiring very little welding.
The Short Span Steel Bridge Alliance has developed standardized plans using standard plate sizes (60”, 72” 84”, 96”, 108”, 120”). The designs were developed to achieve maximum structural capacity and are available to use in the free-to-use, web-based design tool eSPAN140.
The press-brake-formed tub girder system is open source.
SSSBA and WV LTAP Team Up for Steel Bridge Workshop
The SSSBA and WVDOH collaborated on a bridge workshop to discuss the design of steel bridges with cost-effective, time-saving options for states and counties.
On-Demand Steel Bridge Video Series: Learning By Example
A distinguished panel of 8 industry experts to present case studies that offer innovative and cost-effective examples of steel bridge replacement projects.
“Save a Bundle with Tub Girders” – Modern Steel Construction
The Michigan DOT shaved a year off its three year schedule by using bundled press-brake-formed tub girders for a 19 bridge replacement project.