In October 2011, some of the best brains in the business met in Chicago to discuss specific steel bridge system designs for the future, with a focus on economical value, innovation, and Accelerated Bridge Construction (ABC) practices. The group chose a promising shallow steel press-brake tub girder technology and gave the go-ahead to begin research on developing and testing the design.
The system consists of modular galvanized shallow trapezoidal boxes fabricated from cold-bent structural steel plate. The concrete deck is precast on the girder and the modular unit will be shipped by truck to the bridge site.
What are the economical benefits? They include:
- A significant reduction in fabrication costs — estimated as less than half the cost of other currently available proprietary cold-formed box girder systems — due to cold-bending versus cutting and welding of the section.
- A reduction in additional details such as stiffeners and cross frames.
- The potential for accelerated on-site construction due to the stable modular nature of the pre-topped tub girders.
- The ability to be used for both tangent and skewed configurations as well as simple and continuous spans.
The preliminary specimen design has been completed, resulting in modular concepts that are competitive for spans up to 60 feet. The project is now ready to begin the physical testing phase, which will determine the ultimate capacity of the systems and will serve to benchmark analytical studies.
The testing will consist of eight press-brake tub girder specimens. Nucor Corporation, SSAB Americas, and EVRAZ North America have each donated 84” x 7/16” x 480” Grade 50 steel plates, which will be cold-bent to specific dimensions. The specimens will be constructed and tested in three-point bending loading scenarios under both static and cyclic loading in the Major Structures Lab at West Virginia University. See video of the bent-plate folding process below. The testing phase of the project will be completed in early 2014.
The state of Iowa has received an Innovative Bridge Research and Deployment Program grant (IBRD) from the Federal Highway Administration to replace the Amish Sawmill Bridge on Dillon Avenue in Buchanan with this system. Construction on the bridge will begin this summer. The states of Missouri, Oregon, and West Virginia have also expressed interest in pursuing demonstration projects for this system, with the expectation that these modular systems may be competitive for longer-span lengths.
For more information on this and other short span steel bridge design innovations, click here.