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Folded Steel Plate Girder

 The Folded Steel Plate Girder, or FSPG™

Is an economical alternative for simple and short span bridge construction. This innovative yet simple model has a long service life, requires little maintenance, and is designed for accelerated project delivery.

FSPG™ bridges utilize cold-bent steel plates to form an innovative girder shape that provides strength with lighter weight. Concrete deck panels are precast and attached to the girders to form composite units that can be shipped and erected easily and quickly. High-strength concrete closure pours connect the deck panels to complete the superstructure system.


was developed at the University of Nebraska-Lincoln under the direction of Dr. Atorod Azizinamini. The technology is patented by University of Nebraska at Lincoln, with exclusive distribution rights granted to CDR Bridge Systems and HBS.


The development program spanned over seven years and included extensive research, a number of full-scale tests (fatigue, constructability, and ultimate capacity), non-linear finite element modeling, and field trials.

F olded Steel Plate Girders are fabricated from a single steel plate of uniform thickness that is then bent along multiple lines using a hydraulic metal press break to form an inverted tub shaped section. The plate thickness of either 3/8 in. or 1/2 in. can accommodate all span lengths by simply changing the location of the bends. Only the width of the top and bottom flanges and the depth of the web vary depending on span length. However, due to today’s technological constraints of press breaks in the United States, the maximum span length for FSPG™ bridges is currently limited to 60 feet.

The innovative, patented design eliminates the need for internal and external cross-frames because the design generates a large amount of lateral stiffness. The absence of cross frames in the system results in less costly details and significantly reduces the need for welding. This is just one of the reasons why FSPG™ is lighter and more cost effective than other steel alternatives. The open bottom geometry of the folded steel plate girder makes the inspection of the FSPG™ quick and easy compared to traditional box girders. Finally, the hot-dip galvanization process ensures a superior level of corrosion protection.

Finally, our approved fabricators need only retain two different plate thicknesses, so maintaining plates in-stock is now financially feasible. What this means for our clients, especially in emergency situations, is that CDR Bridge Systems can produce girders with much less lead time than other fabricators.




Our facilities can deliver a prefabricated, full depth superstructure solution within 30 days of order to the site, which can be placed and open to traffic in 24 hours.


Our innovative design, coupled with advances in steel material, results in a lighter product with fewer components. The wide top flange eliminates the need for formwork for cast-in-place decks, and material is further reduced because there are no internal or external cross frames, bolts, or stiffeners required.


Less welding, little to no field splices, lack of cross-members, and ease of form work reduce labor costs. Our design reduces the superstructure weight by almost 3.5 times that of concrete and 33% that of traditional steel design. The need for heavy-lift cranes is eliminated, reducing equipment costs and facilitating access to constrained construction areas.


The design features an open-box system for easy inspection and no internal or external cross frames. There are no bolts or welds to inspect along the length of the superstructure where corrosion can take place. There are no fatigue prone details. Finally, our hot-dip galvanization process provides a superior level of corrosion protection.



This construction method utilizes a less-than-full depth subdeck cast onto the folded plate girders, either at an approved precast plant or in the field at a nearby staging area. Folded plate girders are individually topped with a precast sub-deck slab.


These units are then placed side by side in the field with a small closure region (currently 8”) between the slabs of each unit. This closure region is then cast to join the units together. Finally, an overlay is applied to the entire deck to ensure a smooth continuous-riding surface.


A full width precast deck panel configuration begins with bare steel girders placed over their supports. The shear studs are welded to the girders and the girder is then hot-dip galvanized to provide extended service life. Precast deck panels are then match-cast to ensure proper fit.


Once all the panels are set on top of the girders, the slab units are joined together using match-cast integral shear key filled with high-strength epoxy adhesive. Once all the panels are joined, the shear pockets are filled with grout, as in the haunched region between the steel and concrete panels. The grouted shear pockets encase the shear studs, providing composite action between the steel and the concrete. Finally, the closure region is cast to create the finished deck.


Partial Width Precast is another fabrication option with the FSPGS™ and combines elements of the Side by Side construction and the Full Width Precast method. It is a precast option that can be used for structures too wide for the full width precast method. The bare steel girders are placed over the supports. Precast deck slab units are then placed on top of the girders. The precast units span less than the full width of the bridge, typically half of the width, leaving a longitudinal closure region. The slab units are joined together using match-cast integral shear key filled with high-strength epoxy adhesive.


Once all the panels are joined, the shear pockets are filled with grout, as in the haunched region between the steel and concrete panels. The grouted shear pockets encase the shear studs, providing composite action between the steel and the concrete. Finally, the closure region is cast to create the finished deck.


A lthough bridge components have been hot-dip galvanized for many years, CDR Bridge Systems has carefully enhanced the process for maximum effectiveness. Our hot-dip galvanization process provides a superior level of corrosion resistance and is designed to reduce maintenance costs and meet our 100-year service life standard.

Prior to FSPG™, the two primary limitations for galvanizing steel bridges have been transportation costs and galvanizing kettle size and availability. FSPG’s lighter weight and 60 feet maximum span length fully resolve these issues.

Several kettles throughout North America can accommodate our girders.

Galvanized surfaces have been troublesome to paint in the past, limiting color choice to the gray-spangled and mottled appearance of the galvanizing. However, CDR Bridge Systems’ personnel have been educated in recent improvements and the specific procedures necessary for successful painting and top-coating of galvanized steel, providing an enhanced level of corrosion protection and aesthetics.




FSPGS bridges have been full-scale tested for load-carrying capability and performance by multiple independent organizations including the University of Nebraska, Florida International University and University of the Massachusetts at Amherst.

CDR Bridge Systems uses only high-quality, high-strength steel from ISO-certified mills in the United States.

CDR Bridge Systems mills are trained and certified in the cold-steel bending process and re-certified every year.

CDR Bridge Systems' proprietary galvanization process ensures superior corrosion protection and reduces overall maintenance.

CDR Bridge Systems' Quality Assurance Managers and Engineers inspect every component throughout the life cycle of the bridge. From the purchase of the steel from ISO-certified mills through the fabrication process of bending, galvanization, welding, and casting the decks to final installation on site, we are involved and inspecting at every point to ensure CDR quality.

CDR Bridge Systems Folded Steel Plate Girder is now in its second generation. Our fabrication and construction processes are constantly being improved upon and enhanced. Our goal is to continually provide a more competitive product from a quality, cost and schedule standpoint.


Bridge innovation is our business. We continue to improve our design, and the second generation of FSPG will be available in the spring and includes the following upgrades:

Steel-headed bars are eliminated, further reducing the amount of materials and providing simpler details for developing the transfer reinforcement in the closure pour region.

The closure pour region is reduced to 8” from 13”.

Utilizing a full-depth versus a partial-depth deck option reduces time from construction to bridge opening from one week to 24 hours.

Reducing maintenance costs by using a new integrated wall system to eliminate the need for casting on-site, which lessens if not eliminates water leakage into the superstructure component.

Galvanization provides corrosion protection and eliminates the need for the future painting.

Incorporation of cast-integral end-wall system eliminates on-site casting, reduces on-site construction time and minimizes potential for water leakage into superstructure component.



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