Press Brake Steel Tub Girder - Dr. Barth and Dr. Michaelson

County to Save $100,000 Using Innovative Steel Design for Bridge Replacement Project

Topics: Blog, Economics, Press Brake & Folded Plate

If you’re a county/state engineer or a bridge owner, cost is always a deciding factor in which material to choose for your next project. A new design using press-brake-formed steel tub girders (PBTG) is providing a durable, cost-saving solution for short span bridge projects.

A PBTG bridge consists of modular galvanized shallow trapezoidal boxes fabricated from cold-bent structural steel plate. A concrete or Sandwich Plate System (SPS) deck is precast on the girder, making it a single unit. Guardrails can be added, and the structure can be transported by truck to the project site. The unit can usually be installed in one or two days by local crews using their own equipment.

Recently, Buchanan County (Iowa) Engineer Brian Keierleber was faced with a decision on how to replace the Daniel Avenue Bridge. Built in 1956, the span is 63 feet long, 21 feet wide and is posted at 17 tons, but still has a sufficiency rating of 57. It is situated on a Class A Road with two houses directly behind it, making the project site a bit challenging to navigate.

Press Brake Tub Girder

Initially, Brian considered steel, concrete T-beams and even railroad flatcars as bridge replacement options because of cost efficiencies and project site challenges. But when the project was let out for bids, he found out he could save nearly $100,000 with a PBTG bridge, even when specifying high chromate steel. This PBTG bridge bid utilizes the Con-Struct™ prefabricated bridge system. Due to the light weight of steel, Brian can save additional costs by reusing the concrete abutments on the current bridge.

A PBTG bridge is a viable option for projects like this because it’s durable, has a modular design so it is easy to transport, and can be installed by a local crew in one or two days, minimizing traffic delays and saving time and money.

The spans for the Fourteen Mile bridge near East Lynn, West Virginia were installed on August 20, 2019. This is the first PBTG bridge for WV.

PBTG bridges are currently being installed or in service in five states, including Iowa, Ohio, Michigan, Texas and West Virginia. The spans for the Fourteen Mile bridge near East Lynn, West Virginia were installed on August 20, 2019. This is the first PBTG bridge for WV.

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.

Learn more about press brake tub girders→