Short Span Steel Bridges 
Guy Nelson Provides Insight on Steel Press-Brake Tub Girders
In 2015, the first installation of a steel press-brake tub girder bridge (PBTG) for a short span application took place in Buchanan County, Iowa – the Amish Sawmill Bridge. Today, 18 states have installed this innovative bridge system.
The success of PBTG can be attributed to the many benefits it offers to bridge owners, including:
- Cost-Effective (as much as 1/3 less than a standard concrete girder structure)
- Ease of Shipment and Fabrication (requires very little welding)
- Modular
- Accelerated Construction (can be installed in less than a day)
- Design Versatility
SSSBA member Valmont Structures manufactures PBTG bridges. Guy Nelson, Product Development Director, is responsible for the engineering and sales of the Valmont U-BEAM press-brake steel tub girder (PBTG) system. In a question and answer session with the Short Span Steel Bridge Alliance (SSSBA), Nelson provided insight into PBTG – including details of a recent installation of the Evans Mill Bridge in Peoria, IL.
Guy Nelson, Product Development Director, Valmont Structures
Question & Answer with Guy Nelson, Valmont Structures
What makes a PBTG standout over other materials?
The shape of the PBTG provides a superior strength to depth ratio (longer spans, with shallower sections). Furthermore, innovative fabrication methods allows for reduced costs, faster fabrication, shorter lead times than comparable steel and concrete beam products.
What makes Valmont Structures unique?
Valmont recently opened a facility with personnel dedicated to only fabricating our U-BEAMs. Valmont invested $20M in the facility (Jasper, TN) featuring a 60’ long automated press brake, automated shear stud welding, and cold rolling machinery for camber.
Can you explain how you work with counties to tailor your level of service and assistance to meet their needs?
At Valmont, we always express we can do as much or as little as you want. We are steel fabricators and will always facilitate the design of our products, but we have our ESS (Engineered Support Services) group that can provide Engineered drawings, signed and sealed calculations and a load rating for the complete superstructure.
The Evans Mill Road Bridge superstructure was designed by LBYD Engineers. They utilized ASTM A572 GR65 with a hot-dipped galvanized coating. All fabrication of the Valmont U-BEAMs followed AASHTO Construction Specifications and AASHTO AWSD1.5 Welding Code.
The county desired a Valmont U-BEAMTM Complete Bridge System, which incorporates the Valmont U-BEAMTM with a precast concrete bridge deck. This concrete bridge deck was precast atop the U-BEAMs by McCann Precast in Dorsey, IL.
The 70’ long Valmont U-BEAMs where delivered to McCann in 2 pieces, a 50’ long and a 20’ long section, and were bolted together by McCann, prior to casting the concrete. McCann then delivered the final prefabricated bridge system to the construction site in Peoria County.
Is there anything unique about the Peoria Bridge – from a fabricator’s viewpoint?
Yes, this is a 70’ long press brake tub girder U-BEAMTM with a 40 degree skew. As far as we know, this is the longest vehicular PBTG fabricated to date. Adding a skew to this long of PBTG also added complexities to the AASHTO design.
The Evans Mill Road Bridge (Peoria IL) was constructed using steel press-brake tub girders.
Can you explain why Peoria used galvanized steel for this project?
It has been shown that by extending the service life of the bridge structure, counties can increase the condition of their overall bridge inventory – eventually reducing the number of bridges that require replacement, for an end goal of reducing the overall annual expenditures on replacing deficient bridges.
Can you provide insight on how this bridge was transported and set on the bridge site?
The four 70’ long prefabricated bridge units weighed approximately 30 ton, and were delivered on extended length truck trailers. These four bridge units were then installed with a 250 TON GROVE crane.
Why was a prefabricated bridge specified for this specific project?
The county wanted to evaluate the advantages of prefabricated bridge systems; specifically a press-brake formed galvanized steel tub girder prefabricated bridge system, and determine the benefits of installation time, quality of product, extended service life and ultimately reduced life-cycle cost.
Can you discuss the splice on the bridge?
Valmont has one of the longest press brakes in the world at 60’ long, that yields a bent plate as long as 58’ long. Valmont also has some of the largest galvanizing tanks in the United States at 62’ long. Therefore, galvanized U-BEAMs longer than 58’ need to be produced in 2 pieces. These 2 pieces can then be joined either by shop welding, or by a bolted splice.
As the innovation of PBTG is the elimination of fatigue critical weld details, Valmont determined the best solution is a bolted splice connection. This bolted splice connection also has additional advantages:
- All elements can be hot-dipped galvanized.
- Elements can be shipped in pieces on standard trailers.
- Bolted splices are typical steel construction elements that all steel bridge erectors know how to assemble.
In 2023, Guy Nelson and Jeff Simkins (Valmont) presented an overview of press-brake tub girders to members of the Colorado LTAP
(video provided courtesy of Colorado LTAP)
For more information about Valmont Structures, contact Guy Nelson:
Guy Nelson, PE, SE
Business Development Director – North American Structures
Valmont Industries, Inc
28800 Ida Street
Valley, NE 68064
Tel: (616) 813-8514
Guy.Nelson@valmont.com
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.
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