Colorado’s curved hybrid steel bridge shakes up traditional bridge design

Park Union Bridge in Colorado Springs, Colo., inspired by the gravity-defying motion of athletes, masterfully combines truss and arch forms into a curved hybrid steel structure, to pay allegiance to its context and serve as a landmark site providing visual and pedestrian access to key areas in downtown Colorado.

The 76.2-m (250-ft) curved, 300-ton (272-tonne) steel structure floats above an active railyard. Two interlocking loops, stretching from either side of the railyard, connect the museum and the America the Beautiful Park. The bridge’s generous width safely accommodates pedestrians and cyclists alike. At its widest point, an oculus at either side of the bridge frames the museum and downtown to the east, a platform for trainspotting below, and a distinct look out to the Rocky Mountain to the west. In the evenings, lighting along the bridge traces a single vector from one side of the tracks to the other, giving a sense of speed and motion while providing illumination for pedestrians and cyclists.

The shell of the bridge is painted structural steel, the liner painted metal panels, the deck is built in concrete, while the elevator that takes to the top features glass. Stainless steel cable mesh, and a comfort railing in the same material with integrated lighting provide fall protection.

The prefabricated bridge was assembled in a staging area in Houston, Texas and a full fit-up was conducted. The pieces were driven into place using self-propelled modular transporters over the course of a single weekend, minimizing outage for the rail lines and yard. As bridge sections were delivered, the bridge was assembled on the ground to weld each section together. Assembly of the bridge sections was completed in the next month. Almost four months later, the bridge was hoisted and placed onto its abutments in its entirety in a carefully orchestrated process completed within an eight-hour window.

The team for the project consisted of Diller Scofidio + Renfro (DS+R) as design architect, with Anderson Mason Dale Architects as architect of record. Further, Arup served as the structural engineer, with structural engineering for bridge abutments provided by KL&A. Felsberg holt & Ullevig and FUHueng provided railroad consultancy services, KING Fabrication handled steel fabrication, and Kiewit Construction served in the capacity of general contractor.

“The bridge is an exercise in fitness – both in terms of material and geometry. The hybrid steel structure system functions as an arch and a truss, elegantly preserving views from Downtown to the majestic mountain ranges of Pikes Peak,” said DS+R partner-in-charge and lead designer Benjamin Gilmartin.

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