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Steel Press-Brake-Formed Tub Girder
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Steel Press-Brake-Formed Tub Girder

What is a Steel Press-Brake-Formed Tub Girder?

PBFTGs utilize a single steel plate that is strategically bent into a superior structural shape.

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IV creates a virtual world in which to model projects accurately in 3D, then render videos and images as well as immersive visualizations to create interactive simulation products. IV models are built from existing and proposed data, including agency design files (i.e., a Microstation roadway surface), while a game engine powers real-time presentation. When optimized with adjacent infrastructure to produce performance simulation, touch screen kiosks and virtual reality (VR) applications can provide a virtual helicopter tour over a proposed project, for instance.

Project NEON, Nevada's largest and most expensive public works project ever, was the catalyst for the initiative. IV helped convey complex planning and design scenarios to the public while helping project development personnel identify and resolve design and construction challenges, such as site impacts and right of way, geometric, and line-of-sight issues. IV products allowed the traveling public, homeowners, and businesses to see the potential impact of the project on their interests, while addressing their concerns and those of regulatory agencies about safety and environmental impact. As a result, IV vastly enhanced interagency coordination, regulatory review, and approval.

IV supplies much more freedom of camera movement than typical state-of-the-practice project visualizations, which provide views from specific angles. That enables non-outreach products like technical clarity visuals, graphics for related legal cases, landscaping details, and more. While conventional visualizations render various images for delivery via video files from which models are constructed for a given purpose, rapid, real time rendering through IV’s game engine technology eliminates the need to remodel, bringing its overall cost in line with traditional 3D visualization. ​

Our environment is changing, and bridges across the United States are deteriorating at a rate which currently outpaces the available funding to slow or reverse deterioration rates. It is estimated that it will take more than 80 years to fix all current structurally compromised bridges considering current federal and state capital investment levels. With service life as low as 35 years for the current baseline practice, the demand for newly constructed bridges will greatly exceed our future capacity. 

In addition to not meeting aspirational service life timeframes, each current baseline practice has its own specific associated problem to solve. Steel Press-Brake-Formed Tub Girder (PBFTG) uses proven material and current design standards, combined with new fabrication and construction techniques, to produce a bridge superstructure with reduced maintenance cost and shortened construction time, that lengthens the service life over the current bridge superstructure baseline practice.

PBFTGs utilize a single steel plate that is strategically bent into a superior structural shape. The plate is cold formed into a U shape with a press brake, with each bend occurring along the plate's longitudinal axis. The formed steel plate bend radius exceeds the minimum requirement, based on AISC and ASTM cold forming guidelines, and is designed for infinite fatigue life due to lack of connections and discontinuities.  These fabrication advancements further lengthen the service life of the steel tub girder over other fabrication technologies. Additionally, a hot-dipped galvanized coating can be applied to the PBFTG to further lengthen the maintenance-free service life.  By applying a Duplex coating, painting over hot-dip galvanized steel, and with appropriate composite concrete bridge deck detailing, PBFTG will meet the AASHTO Committee on Bridges and Structures strategic objectives of extending bridge service life to an anticipated 100 years.​

Resources

Steel Press-​Brake Tub Girder Presentation

Contacts

Matthew J. Chynoweth, P.E.

Chief Bridge Engineer
Director, Bureau of Bridges and Structures
Michigan Department of Transportation
Phone: 517-243-4302
Email: ChynowethM@michigan.gov

Joe Alderson, M.S. & P.E.
Structural Project Manager
Missouri Department of Transportation
Central Office – Bridge Division
Phone: 573-522-8722
Email: Joseph.Alderson@modot.mo.gov

Timothy Leaf, P.E.
Structural Project Manager
Missouri Department of Transportation
Central Office – Bridge Division
Phone: 573-526-1505
Email:Timothy.Leaf@modot.mo.gov

Guozhou Li, P.E.
Assistant Chief Bridge Engineer
Pennsylvania Department of Transportation - Bridge Office​
Phone: 717-214-8773
Email: guli@pa.gov

Guy Nelson, P.E., S.E.
Structural Engineer
Product Development Director
Valmont Structures
Phone: 616-813-8514
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