Short Span Steel Bridges 
Saving Time in Michigan with Press-Brake-Formed Steel Tub Girders
Project Overview
In 2017, the St. Clair County Road Commission (SCRC) chose to replace two 70-year-old severely deteriorated steel superstructures with a new press-brake-formed steel bridge superstructure. These existing bridges carry the Marine City Highway, which is the main thoroughfare into and out of Marine City, Michigan for commercial and school traffic. The highway is a two-lane road that handles more than 10,000 vehicles per day. The two bridges included a 25-foot-span steel beam bridge (Structure 4-08) and a 35-foot-span steel beam bridge (Structure 4-09) on a 45-degree skew.
Setting the press brake tub girders on the abutments.
Originally built in the early 1950s, the steel beam bridges were designed for H-15 loading and had reached the end of their long 60-year-service lives. The existing beams for both bridges consisted of hot-rolled W18 wide flange sections, 18 inches deep. The entire bridge cross-section depth, including concrete deck and overlays, totaled 2′-4.5″.
The traffic detour route for each bridge closure included seven miles of gravel roads and more than 15 minutes out of the way for drivers, so SCRC considered options to expedite the schedule for a full-closure construction project. To reduce the duration of the construction closure and reduce costs, it was imperative to utilize and rehabilitate the existing abutments, requiring the new superstructure to match the existing superstructure’s weight and depth. SCRC also wanted to maintain constructability by county maintenance crews. The best option for SCRC was the press-brake-formed steel tub girder bridge system, which allowed the team to meet all of these goals.
The original bridges was built in the early 1950s.
Methods of Construction
The existing abutments were reused and rehabilitated, eliminating costly and time-consuming substructure demolition and replacement work in the water. This was made possible by the light weight of the press-brake-formed steel girder superstructure, which provided no additional dead load pressure on the spread footing abutments. Special steel tub girders were fabricated to match the depth of the existing superstructure so that no modifications were needed for the existing abutment bearing elevations. This also reduced the roadway approach pavement replacement limits and saved costs.
The existing abutments were reused and rehabilitated.
Fabrication of the Bridge System
The Con-Struct™ Press-Brake-Formed Steel Prefabricated Bridge System was chosen for its light weight, adjustable depth, low cost, integral backwalls and ease of construction. Con-Struct™ consists of a precast concrete deck on galvanized, press-brake-formed steel tub girders. The superstructure was prefabricated by ADL Systems in Portland, Michigan, which provided a quality, cost-effective final product. The Con-Struct™ Prefabricated Bridge System was designed for the required HL-93 (MOD) Michigan Department of Transportation (MDOT) live load and met all applicable MDOT and AASHTO design criteria. The 8-inch-thick precast concrete deck was overlaid with a thin epoxy overlay which provided the final driving surface and additional protection from deicing salts. The galvanized steel tub girders were designed to be 18 inches deep, providing a total superstructure thickness of 2′-4″, which closely matched the depth of the removed superstructure. The Con-Struct™ superstructure was manufactured with integral backwalls so there was no need to cast substructure concrete in the field, further expediting the installation schedule.
The galvanized steel tub girders are e 18 inches deep.
Shipping and Erection
Both superstructures were transported to the construction site in six individual units. The 25-foot-span units of Structure 4-08 weighed approximately 10 tons and required only a county-owned excavator for erection. The 35-foot-span units of Structure 4-09 weighed 15 tons, so the county chose to rent a 150-ton crane to set them. For Structure 4-08, the superstructure units arrived at the job site before 8:00 a.m. and were all set in place by the county before 11:30 a.m. The crane for Structure 4-09 arrived at roughly 9:00 a.m. and was ready to lift the bridge units within an hour. Delivery of the superstructure units was timed to coincide with the readiness of the crane. By 1:00 p.m., the six units for Structure 4-09 had all been set in place.
The superstructure was transported to the construction site in six individual units.
The six individual units were then tied together with a concrete closure pour. The SCRC maintenance crew cast a 6-inch-wide High Performance Concrete deck joint, creating a continuous 41’-6”-wide concrete bridge deck. Transpo Industries T-17 Methacrylate Polymer Concrete was used in the deck joint. The deck joint width and rebar lap length were specifically designed for the T-17 material based on rebar development length testing provided by Transpo Industries.
The bridge has a continuous 41’-6”-wide concrete deck.
The deck for Structure 4-08 was overlaid with a thin epoxy overlay to further protect the concrete driving surface. Due to weather limitations, the thin epoxy overlay on Structure 4-09 will be placed in Spring 2018 under temporary lane closures.
A thin epoxy overlay was used to further protect the concrete driving surface.
Final Product
Over the next three days, the roadway approaches were paved with asphalt, and the drainage ditches in all four quadrants were regraded and seeded. Guardrail was installed on the bridge deck utilizing anchor bolt holes that were precast into the Con-Struct™ bridge deck fascia units. The St. Clair County Road Commission was able to successfully replace these two deteriorated bridges in just over a week by using innovative prefabricated structural elements. With the use of the Con-Struct™ Prefabricated Bridge System, this project provided a new structure with a service life of over 60 years that is sustainable, cost-effective, aesthetically pleasing and environmentally friendly.
Structure 4-08
Structure 4-09
Read additional information about this project from Valmont Structures.
Marine City Highway Bridge Replacement Project Team
Owner
St. Clair County Road Commission
William Hazelton
Director of Engineering
Tel: 810.388.4030
Email: whazelton@stclaircounty.org
Website: http://www.sccrc-roads.org/
Manufacturers
Willbanks Metals
Gabriel Castillo
General Manager
Tel: 918.836.2929
Email: gabe.castillo@willbanksmetals.com
Website: http://www.willbanksmetals.com/
ADL Systems, Inc.
Ryan Vroman
Project Manager
Tel: 517.647.7543
Email: central@adlprecast.com
Website: http://adlprecast.com/
Engineer
Valmont Structures
Guy C. Nelson, P.E., S.E.
Structural Engineer
Tel: 616.261.8630
Email: Guy.Nelson@valmont.com
Website: http://www.constructbridge.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.
Case Study
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Watch this four-part, on-demand video series featuring expert-led case studies on cost-effective, resilient short span bridge projects—now available with downloadable presentation materials.
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Valmont Structures developed a summary outlining how the new AASHTO 10th Edition Bridge Design Specifications impact the use of press-brake tub girders (U-BEAMS) in bridge construction.
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