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I-205 Portland LRT Bridge
Portland, Oregon
The I-205 Bridge is a part of the 5.5 mile extension of Tri-Met’s Light Rail Line in northeast Portland from the Gateway Station to the Portland International Airport. The $125M project completes the final link from downtown Portland to the airport and is being designed and constructed by the Bechtel Infrastructure Corporation’s design/build team. As a subconsultant to Bechtel, Finley McNary is providing both design and construction engineering services for the 1160 ft. flyover structure at I-205, near the airport.
The structure consists of a 300 ft. long approach unit consisting of precast Bulb-T girders and an 860 ft. long cast-in-place segmental unit. The four-span segmental unit has spans of 180 ft., two spans at 250 ft., and 180 ft. The 34 ft. wide box girder carries two tracks of light rail traffic.
The CIP segmental structure was selected in order to minimize impacts to I-205 traffic, while still accommodating the geometric requirements of long spans and a horizontal radius curvature of 550 ft. The box girder varies in depth from 13 ft. to 7 ft. and is supported monolithically on single, 8 ft. diameter columns and drilled shafts. The substructure design is complicated by high seismic design force requirements with a wide variety of soil conditions and pier heights.
The structure was built in balanced cantilever using a single pair of conventional form travelers. With a tight project schedule, the substructure work began in April of 1999 (prior to completion of the final superstructure design) with completion of the entire I-205 Bridge in April of 2000. The I-205 Bridge was critical for the overall project schedule, in that it allows construction access to the median of I-205. The first of three cantilevers was completed in November of 1999 and the entire structure was completed by early spring of 2000. The substantial completion date for the entire project is July of 2001.
Finley McNary prepared integrated segment drawings, geometrical control of casting, erection, and procedural manuals, casting curves, analysis of construction loading, design of erection equipment and falsework, post-tensioning calculations, and design office support.
Owner:
Oregon Department of Transportation
Client:
Bechtel Infrastructure Corporation
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