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January 25, 2016

National finalist: Gold award
Structural systems

Photo courtesy of HNTB
Tilikum Crossing is the first bridge to be built across the Willamette River in Portland since 1973. The car-free structure serves buses, light rail, bicyclists and pedestrians.

Project: Tilikum Crossing
Client: Tri-County Metropolitan Transportation District of Oregon

Tilikum Crossing, also known as Bridge of the People, is one of a dozen bridges in Portland that spans the Willamette River. But it is the first-of-its-kind, long-span, automobile-free bridge designed specifically for pedestrian and bicycle traffic, buses and light rail, with streetcar use planned for the future.

HNTB served multiple roles in the design and construction of this bridge, including developing concepts for bridge types; completing engineering feasibility analyses, cost estimates and risk assessments; and assisting the Tri-County Metropolitan Transportation District (Tri-Met) with evaluating and screening bridge types.

The firm also was responsible for complex foundation design, analysis of seismic hazards and liquefaction, and in-river explorations and in-situ testing.

Tilikum Crossing is composed of a 780-foot main span and two 390-foot end spans built by the segmental concrete cantilever construction method. Segments are 75 feet wide and 35 feet long. The bridge tower height was limited to 100 feet above the deck, necessitating the use of solid towers with a saddle system rather than conventional hollow-core towers of much bigger size. Fourteen-foot bike-pedestrian paths border each side of the bridge, flaring out into belvederes at the towers to allow people to stop and enjoy the bridge’s panoramic views.

Tilikum Crossing is the first bridge in the United States to use commercially available multi-tube saddle design, which allows each cable to run continuously from the deck through the top of the tower and back down to the other side of the deck. An aesthetic lighting system uses 178 LEDs to illuminate the cables, towers and underside of the deck, with colors and motion of the lighting changing along with the river’s speed, height and water temperature.

Completed on time and $15 million below the engineer’s estimate, Tilikum Crossing fulfilled Tri-Met’s desire that it be a “beautiful, affordable and constructible bridge” that would enhance transportation in the metropolitan area and ensure Portland would be recognized around the world.

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