Douglas - Chief Joseph Dam Bridge Replacement
Project Number: 1744
From milepost 0.37 to milepost 0.64
RATA Funds: $940,200
Legislative District: 12
Status:
Date Approved: 2013
The Chief Joseph Dam Bridge is a 308 foot long bridge with a 126 foot Howe truss main span and timber approach spans on each side. The historic truss was originally built in 1958 and was designed for H15-S12 live load and a 26’-4” wide timber deck. The bridge was rehabilitated in 2003 by replacing both approach spans and replacing the entire deck with a fiber reinforced polymer (FRP) deck system. The new deck was widened to 32’-0” and new curbs and railing were added. The rehabilitation in 2003 was funded through FHWA Innovative Bridge Research Council (IBRC) program.
Even though this bridge was rehabilitated in 2003, the truss did not have the capacity to effectively carry today’s legal truck loads. Much of the load carrying capacity of the truss was taken up by the additional dead load of the rehabilitated deck. The dead loads from the rehabilitated deck we're approximately 1.7 times heavier than the original deck loads.
The re-decked bridge was restricted to a single lane; truck loads were directed down the center of the bridge in order to minimize the loading on each truss. As an important freight traffic route on Pearl Hill Road and Douglas County, the review of specialized bridge consultants found that anything other than replacement would be a waste of public funds.
The replacement removed the existing bridge and truss. A new single span structure was designed and constructed to completely span over the Foster Creek channel. The design spans 240 feet and utilizes post-tensioned spliced I-girders with a cast-in-place concrete deck. Precast segments were shipped to the site and post-tensioned together prior to slab casting. Walls to retain new approach fill are 50 to 60 feet long on each side. A single span structure saves costs and construction time. Additionally, concrete girders provide a durable bridge with minimal future maintenance costs.
Even though this bridge was rehabilitated in 2003, the truss did not have the capacity to effectively carry today’s legal truck loads. Much of the load carrying capacity of the truss was taken up by the additional dead load of the rehabilitated deck. The dead loads from the rehabilitated deck we're approximately 1.7 times heavier than the original deck loads.
The re-decked bridge was restricted to a single lane; truck loads were directed down the center of the bridge in order to minimize the loading on each truss. As an important freight traffic route on Pearl Hill Road and Douglas County, the review of specialized bridge consultants found that anything other than replacement would be a waste of public funds.
The replacement removed the existing bridge and truss. A new single span structure was designed and constructed to completely span over the Foster Creek channel. The design spans 240 feet and utilizes post-tensioned spliced I-girders with a cast-in-place concrete deck. Precast segments were shipped to the site and post-tensioned together prior to slab casting. Walls to retain new approach fill are 50 to 60 feet long on each side. A single span structure saves costs and construction time. Additionally, concrete girders provide a durable bridge with minimal future maintenance costs.