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Big Cottonwood Canyon Loop Road



Developers of a new upscale housing community near Utah’s Wasatch Mountains wanted to create an access bridge that provided a strong welcoming presence. But the difficult terrain created challenges in blending function and aesthetics. To achieve these goals, designers produced two reinforced concrete bridges, including a five-span, 450-foot-long structure with a switchback curve along an 80-foot radius of the centerline, which also featured a 12 percent grade.

Typical solutions for curved highway bridges include straight girders that form tangents between supports or curved steel girders. In this case, the curve was too severe for tangent girders without reducing the span lengths to less than 30 feet, and curving steel girders proved too costly. In addition, post tensioning wouldn’t have been effective on such a tight radius. The cast-in-place reinforced concrete girders met the needs creatively and effectively.

The entire structure, from its footings to parapet, features conventionally reinforced, cast-in-place concrete. Spread footings of 25 square feet support 7-foot-diameter single column-bent supports. Full-depth integral bent caps, each 5 feet wide, support the concrete box superstructure, which consists of a three-cell concrete box girder.

The lower, five-span bridge features three curved middle spans, connecting to the two straight end spans. The entire structure used more than 2,500 yards of concrete and 415,000 pounds of Grade 60 reinforcement bars. The bridge’s curvature was so severe that longitudinal #8 deck bars were bent at the fabricator’s shop to achieve the proper shape. Smaller #5 bars were bent in the field and spaced along the deck’s outside edge at a wider spacing than along the curve’s inside edge. The top deck and parapets feature epoxy-coated reinforcing bars, with the other sections using uncoated reinforcing steel (rebar).

The parapet included recesses for LED lighting tubes along the top of the barrier and conduit, with blockouts for ornamental floor lights. The completed bridge was stained to better fit with the natural environment of Big Cotton-wood Canyon while still making a strong structural and architectural statement.

A total of 415,000 pounds of Grade 60 reinforcing steel (rebar) was used in this structure.

Project Details

Location:

Salt Lake City, UT

Owner:

Wasatch Pacific LLC, Salt Lake City, UT

Designer:

Michael Baker Jr. Inc., Midvale, UT

Contractor:

Ralph L. Wadsworth Construction Co. Draper, UT

Concrete Supplier:

Harper Ready Mix, Salt Lake City, UT

Reinforcing Bar Fabricator:

Farwest Steel Corp., Eugene, OR

Total Project Cost:

$170/ft2 (bridge only)

Total Project Size:

450 ft, Overall Span

Resources