Willamette River Transit Bridge
Kiewit led the team to design and construct this cable-stayed bridge over the Willamette River, a vital element of TriMet’s new 7.3-mile light rail link connecting downtown Portland, the South Waterfront, the city of Milwaukie, and North Clackamas County. This signature bridge is the nation’s largest transit-only bridge and carries light rail trains, streetcars, buses, pedestrians, and cyclists, but no private vehicles. It can provide a passageway for emergency vehicles.
The bridge is designed around two distinctive, H-shaped towers. Each 180-ft. tower sits on an oval in-water pier and, together, support 3.5 miles of stay-cables. Each pier is founded on six 10-ft.-diameter drilled shafts. The 1,720-ft.-long bridge has a 780-ft. long main span with a 31-ft.-wide deck that runs through the “H” of the tower legs, accommodating two light rail tracks. The bridge has 3440 track ft. of embedded rail, incorporates special track work, and accommodates systems designed and installed by a follow-on contract. Outside of the tower legs, separated from the center section by the cable stays, are 14-ft.-wide pedestrian and bike paths. The typical deck width is 75 ft., widening at the towers as the multi-use path cantilevers around the tower legs.
The structural system lies outside the conventional parameters for cable-supported bridges. The slender deck is typical of a true cable-stayed bridge, yet the tower height and associated rise of the stay cables trends towards the layout for an extradosed bridge. The rail load puts significant demands on the tower and anchor piers, as well as the deck section in the boundary zones. Several value engineering ideas reduced the schedule, geotechnical risk, environmental impacts, and TriMet’s costs.
The project received the following awards:
- 2016 – Engineering News Record (ENR) Northwest Best Project Award – Highway/Bridge Category
- 2016 – Engineering, Honor Award, American Council of Engineering Companies (ACEC)
- 2016 – Engineering, Project of the Year, American Council of Engineering Companies (ACEC) of Oregon
- 2016 – Engineering People’s Choice Award, American Council of Engineering Companies (ACEC) of Oregon
- 2015 – Bridge, Bridge Award of Excellence, American Segmental Bridge Institute (ASBI)
- 2015 – Bridge, Excellence in Concrete, Oregon Concrete and Aggregate Producers Association (OCAPA)
- 2015 – DBE/SBE Subcontracting, Champion of the Year, DBE Achievement ,Tri-County Metropolitan Transportation District of Oregon (TriMet)