Press-Brake-Formed Tub Girders


Press-brake-formed tub girder is a new technology for short span bridge applications. In 2009, the Federal Highway Administration (FHWA) challenged the North American steel industry to “develop a cost-effective short span steel bridge with modular components which could be placed into the mainstream and meet the needs of today’s bridge owners, including Accelerated Bridge Construction (ABC).”

The Short Span Steel Bridge Alliance (SSSBA) organized the Modular Steel Bridge Task Group—consisting of 30 organizations representing the SSSBA, Steel Market Development Institute, National Steel Bridge Alliance, National Association of County Engineers, steel bridge fabricators, university faculty members, steel manufacturers, government organizations, and bridge owners--to develop ideas to meet this challenge. Led by Karl Barth, Ph.D., P.E., Samples Professor of Civil and Environmental Engineering at West Virginia University, the group decided in October 2011 that a shallow steel press-brake tub girder technology provided the best opportunity to meet the FHWA goals for economic value, innovation, and ABC practices. A preliminary specimen design was developed for spans up to 60 feet. The idea went from concept to reality in just three years, a significant accomplishment.

Three years of testing then commenced at West Virginia University on eight press-brake tub girder specimens donated by Nucor Corporation, SSAB Americas, United States Steel Corporation, and EVRAZ North America. The specimens were cold-bent to specific dimensions and then tested in three-point bending loading scenarios under both static and cyclic loading in the Major Structures Lab at West Virginia University. Initial testing was completed in 2014. Additional testing was completed in 2016.

In the meantime, Buchanan County (Iowa) Engineer Brian Keierleber, P.E., submitted a proposal to replace the Amish Sawmill Bridge at 1358 Dillon Avenue in Fairbank, Iowa with funding from the FHWA’s Innovative Bridge Research and Deployment (IBRD) Program. The $350,000 grant was awarded on the basis of using a trapezoidal bent steel girder section supported on Geosynthetic Reinforced Soil (GRS).

Construction on the Amish Sawmill Bridge began in late summer 2015 and was completed in December 2015. The deck for this project was cast-in-place, rather than using modular pre-cast deck units, which added to the time of construction. The bridge was dedicated on January 8, 2016 with a ribbon-cutting ceremony featuring several government and transportation officials.  


The press-brake-formed tub girder system consists of modular galvanized shallow trapezoidal boxes fabricated from cold-bent structural steel plate. The 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 is in the process of developing standardized plans using standard plate sizes (60”, 72” 84”, 96”, 108”, 120”). The designs were developed to achieve maximum structural capacity. 

The press-brake-formed tub girder system is open source. 


Press-brake-formed tub girders are versatile for multiple-deck options. They can be used for both tangent and skewed configurations, as well as simple and continuous spans. They are recommended for single spans up to 60 feet or less. Spans may be spliced together to form a multi-span bridge greater than 60 feet. 


The stable modular nature of the pre-topped tub girders allow for accelerated on-site construction. There is a reduction in additional details such as stiffeners and cross frames. The concrete deck is precast on the girder and the modular unit can be shipped by truck to the bridge site.


The press-brake-formed tub girder system offers significant cost savings, ease in shipment and fabrication, accelerated construction and design versatility, with the potential to replace thousands of short span bridges in the next decade. Several states have expressed interest in this new technology - Iowa and Ohio have installed press-brake-formed tub girder bridges.

For More Information

Please contact Dr. Karl Barth at

Note: The innovators and researchers responsible for developing and testing this technology are available to provide presentations and workshops to state and federal Departments of Transportation, county engineers, and other interested groups. For more information or to schedule a presentation/workshop, please contact Rich Tavoletti at or 412.458.5822. 

Read more in Engineering News-Record

Read more in STRUCTURE Magazine.


The Amish Sawmill Bridge located in Fairbank, Iowa was dedicated with a ribbon-cutting ceremony featuring several government and transportation officials on Friday, January 8, 2016. Despite the cold, snowy weather, the mood was celebratory as officials dedicated the first-of-its-kind structure. Read more about the ribbon-cutting ceremony. 

Read more about the Amish Sawmill Bridge (Case Study).



For the Cannelville Road Bridge project, after the plate was formed, a thin lightweight Sandwich Plate System (SPS) deck was bolted to the girder in the fabrication shop and guardrails were added, making it a modular unit that could be quickly assembled at the bridge site. The offsite fabrication process saved 3-4 months of construction time. Both PBTG/SPS modules were erected and set on the abutments in just 22 minutes. The new bridge was financed in part with research funding from the Federal Highway Administration due to the integrated PBTG/SPS deck demonstrating Accelerated Bridge Construction. Read more here (Case Study). 


The Con-Struct™ Prefabricated Bridge System consists of a precast concrete deck cast compositely on a galvanized press-brake-formed steel tub girder. This system was chosen by the County of Bexar (Texas) Public Works Department for several reasons, such as the ability to reduce the construction schedule by up to 45 days. Read more here (Case Study - "County of Bexar Public Works Department Chooses Con-Struct™ Prefabricated Bridge for Flood Control Culvert Replacement Project"). It was also chosen by the St. Clair County (Michigan) Road Commission to minimize construction closures and traffic disruptions, as well as cost savings. Read more here (Case Study - "Saving Time in St. Clair County With Press-Brake-Formed Steel Tub Girders").