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Tilikum Crossing Transit Bridge – Portland, Oregon
In December 2014, construction was substantially completed on Tilikum Crossing Transit Bridge, a new concrete cable-stay bridge crossing the Willamette River in Portland, Oregon. The first of its kind in the U.S., the cable-stayed transit-only bridge will carry light rail trains, buses, pedestrians, bicyclists, and future streetcars. Named Tilikum Crossing, “Bridge of the People,” the landmark bridge is the feature component and vital element of the Portland-Milwaukie Light Rail Transit Project to reduce congestion and provide efficient travel along the 7.3-mile light rail corridor connecting downtown Portland, the South Waterfront, the City of Milwaukie, and North Clackamas County.
Innovation of Design and/or Construction
Design and construction innovations were the key to success for this design-build project. The team designed tower foundations that retained the required aesthetic while reducing the footprint and number of deep shafts in the river, using a sophisticated testing program to prove shaft capacities well in excess of standard design values. The high seismic environment and liquefiable, contaminated soils were a particular challenge that gave the team a competitive edge: our integrated seismic design avoided removal and disposal of hazardous material and ground improvement by engaging the continuous superstructure to transfer seismic demands from the liquefiable banks to the stiff main piers.
The team drew upon their collective segmental experience to develop a cast-in-place erection system that used conventional form travelers and temporary stay cables for casting in half-segment lengths. The team also used stay cable technology to provide a replaceable tie-down required for the extreme train loading-induced uplift in the back spans. The slender tower design incorporated the first domestic application of contemporary saddle details for a transit bridge, requiring special erection controls for cantilever construction and staged stay installation. The team had a particular challenge with a stepped navigation clearance across the main span that led to an innovative split-edge girder stay anchor, recessing the entire anchorage within the soffit of the deck that added the necessary 2 ft. of clearance
Rapid Construction
Construction of Tilikum Crossing defined the critical path for opening the client’s entire light rail line. Parallel hazardous material remediation by the property owner on the west shore complicated access and scheduling at the outset of the project. The design-build team partnered with the client from notice-to-proceed, meeting on a weekly basis to advance schedule throughout the project. The team took advantage of the design-build format to advance construction of the main river piers while completing design of the superstructure. Cooperation and coordination between the contractor, designer, reviewers, and client were vital to success, in part by review of the foundation design innovations that led the project activities, and that had to be choreographed with the in-water work windows in the Willamette River. Form traveler-based construction was accelerated by casting on both towers in parallel. As a result, the project was finished six weeks ahead of schedule, allowing added time for the client to test systems and safely train operators.
Aesthetics and/or Harmony with the Environment
The bridge is now the brightest star in the family of Portland bridges. With some celebrations past, there are more to come as the city boasts of its new icon. Images of the bridge with Mt. Hood in the background have already been the subject of architectural conference, and the bridge is featured in images of the city, occupying a key position in local literature. In addition to complying with the challenging environmental regulations related to construction in a prime salmon river, the team’s design innovations for reducing foundation size and eliminating handling of hazardous waste were a major enhancement to the project’s environmental footprint. And certainly, the very purpose of the bridge as a public transit facility is heralded for reducing the carbon footprint of the transportation system in the Portland region.
Cost Competitiveness
The client placed great value on the high aesthetic content of the design, and used the design-build delivery format to get maximum value for the most competitive cost. The project was delivered under budget and within the original schedule requested by the client. A few unexpected challenges, such as extended third-party permit reviews and approvals and revisions to aesthetic guidelines, threatened to increase the budget and schedule. However, for each occurrence, the team partnered with the client to re-sequence construction, add resources, or modify the design review schedule to keep the project on target.
Minimization of Construction Impact on the Traveling Public
Construction access for personnel and materials was in downtown Portland, requiring continuous coordination with numerous local stakeholders and downtown commuters. However, the major mitigations for travel impacts were associated with river traffic and the heavily used Springwater Corridor trail on the east shore. The team coordinated marine activities with operations of Portland Spirit River Cruises, whose adjacent dock had to remain operational throughout the project.
Jury Comments
Great example of the competitiveness of segmental bridges in a design-build environment. Highly aesthetic cable-stayed structure with special attention given to pedestrian access. Showcases how a segmental solution can provide both strength and slenderness for long-span cable supported bridges. This bridge is outstanding in so many ways. The design-build team finessed every detail in producing a great technical achievement with iconic aesthetics. From the segmental industry’s perspective, this project further demonstrates the applicability of segmental and cable-stayed bridge construction for a wide variety of transit projects.
2015 ASBI Bridge Award of Excellence
Category: Mass Transit / Rail Bridges
State:
Oregon
Owner:
Tri-County Metropolitan District of Oregon
Owner’s Engineer:
HNTB Corporation
Designer:
T.Y. Lin International
Design Build Team:
Kiewit Infrastructure West Co.
Contractor:
Kiewit Infrastructure West Co.
Construction Engineering Services:
T.Y. Lin International
Construction Engineering Inspection:
Cooper Zietz
Formwork for Precast Segments:
Kiewit Infrastructure West Co. (Supplier) and Parkin Engineering (Inspection)
Form Travelers for Cast-in-Place Segments:
Kiewit Infrastructure West Co.
Erection Equipment:
Kiewit Infrastructure West Co.
Post-Tensioning Materials:
Schwager Davis, Inc. (Supplier) and Liberty Steel (Installation)
Stay Cable Materials:
Freyssinet
Bearings:
R.J. Watson, Inc.
Expansion Joints:
Watson Bowman Acme Corp., and STV Inc./Atlantic Track
Prepackaged Grout:
Williams Form Engineering Corp.
