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Ann Arbor, MI - AlumaBridge, LLC of Ann Arbor, MI has completed the successful fabrication of an aluminum bridge deck for the St. Ambroise River Bridge in Quebec, Canada. Two large panels, each measuring 32.9’ (10040 mm) x 12.3’ (3750 mm) x 8.0” (203.2 mm) deep, were required. The deck was shipped on December 10, 2014. The panels have been received, inspected and approved by the bridge owner, Ministry of Transportation – Quebec.

HFW Friction Stir Welding

Unique Set of Specifications

The project resulted in a number of fabrication advancements due to a unique set of specifications that had to be met. For example, AlumaBridge devised a way to attach the panels to galvanized steel girders without bolting the deck to the beams. This was accomplished by steel clamps (angles) that will be attached to the underside of the deck, but wedge on either side of the girder’s top flanges.

During preliminary design, AlumaBridge had to work with the existing girder spacing. This meant bridge engineers had to design unique aluminum extrusions to achieve the proper deck width. The design process also needed to consider clearances for fasteners between structural web members within the extruded aluminum profile. In addition, the curb sides of the deck had to provide a closure and structural support for the deck-mounted crash barrier. Therefore, the deck could not be trimmed to meet the required bridge width. To solve this problem, AlumaBridge designed a structural end extrusion that can be trimmed to provide deck panel width adjustability. The end extrusion was also designed to accommodate a deck-mounted crash barrier as well as a closure needed along the edges of the deck. Additionally, a special extrusion was introduced that is half the width of the base extrusion profile of 12.0” (304.8 mm). This extrusion made it possible to build the panel to the required width.

A design breakthrough was achieved with a splice joint that accelerates bridge construction and reduces the number of fasteners required. It was also important to create a positive connection at the bottom of the splice joint between panels where it rests on top of the girder. As noted above, the deck panels cannot be bolted to the beams, but each panel must be fastened together. The top flanges of the splice nest together with an overlapping flange and recess. The splice joint is fastened together by a single row of blind fasteners that are flush with the deck surface and utilize countersunk holes along the length of the splice. This splice joint design cuts the typical number of bolts in half and accelerates installation. At the bottom of the splice joint, a tongue and groove is incorporated into the extrusion profile for a positive connection. 

At the abutments, the deck is sealed with a 0.79” (20 mm) one-piece closure plate that is mechanically fastened and runs the full width of the deck. Holes in the plate are predrilled at the factory as well as matching holes that are tapped in the deck for quick field installation.

Controlling weld shrinkage and holding tolerances on such large panels were critical. The top flange of each extruded aluminum profile is 0.850” (2.16 mm), while the lower flange is 0.350” (8.9 mm). Each panel incorporated four unique extrusion profiles – base, half, splice, and end extrusions. The range of extrusions required, together with two very different flange thicknesses, added to the complexity of friction stir welding utilized by AlumaBridge.

Previous aluminum bridge decks were fabricated with gas metal arc welding or earlier versions of friction stir welding. By contrast, AlumaBridge was able to deliver the St. Ambroise River Bridge deck with fully consolidated welds that achieve superior dimensional characteristics across the entire 32.9’ (10040 mm) x 24.6’ (7500 mm) deck assembly:

– Flatness Average: 0.37” (9.4 mm)
– Straightness: 0.21” (5.4 mm)
– Squareness: 0.167” (4.2 mm)
– Width: 0.125” (3.2 mm)

Satisfying the unique and challenging set of specifications from the Ministry of Transportation – Quebec made the fabrication of the St. Ambroise River Bridge a breakthrough achievement in the industry. AlumaBridge innovation met the specifications with a commitment to advancing and scaling aluminum bridge deck technology. AlumaBridge is providing new solutions for bridge owners to address accelerated bridge construction and rehabilitation.

The L.B. Foster Company is the North American distributor for AlumaBridge products. 

lbfosterus en 19 January 2018 news/details/2018-01-19-aluminabridge-completes-fabrication-of-aluminum-bridge-deck