I-5 Interstate Bridge (NB) Trunnion Shaft Replacement
This project involved the replacement of the existing trunnion/sheaves, bearings, and wire rope assemblies on the south tower of the vertical lift span of the Interstate 5 (I-5) northbound Interstate Bridge in Portland, Oregon. The I-5 Interstate Bridge crosses the Columbia River between Portland, Oregon, and Vancouver, Washington, providing the only continuous north-south interstate route on the West Coast from Canada to Mexico.
Work included constructing a 150-foot-high temporary support structure on the existing bridge lift tower to support the 760,000# counterweight. After this work was complete, the northbound freeway was shut down for nine days to remove and replace the trunnion/sheave and bearing assemblies (two each) and replace the 2-inch diameter x 180-foot-long wire ropes (32 each). Vertical jacking and temporary support of the counterweight was required in order to relieve the strain on the wire ropes supporting the lift span deck to facilitate removal. A large service crane on a barge was utilized to support the falsework tower construction and trunnion/sheave replacement work that took place 180-feet above the bridge deck and 240-feet above the Columbia River.
This bridge restoration project included approximately two years of fabricating components in Alabama and ended with an intense traffic coordination effort to perform the restoration portion of the work on-site.
During the nine-day closure, Hamilton crews worked round the clock to complete the work required in the trunnion replacement. Staging traffic during this timeframe required a temporary freeway crossover to be constructed to allow both northbound and southbound traffic to run on the southbound bridge. This work required removal and replacement of existing median barrier on both the Oregon and Washington sides of the bridge, as well as the use of 3,400-feet of moveable zipper barrier. This barrier was moved twice daily during the nine-day closure to allow two lanes of southbound/one lane of northbound traffic in the morning and two lanes of northbound/one lane of southbound traffic in the afternoons.
The night before the closure, ODOT canceled the closure due to wildfires and the need to keep potential evacuation routes unrestricted. The closure was delayed 1 week. The Hamilton team collaborated with all stakeholders and subcontractors to successfully manage the new closure date. Crews worked around the clock to accomplish the work. The work completed was a success on many fronts with Hamilton fully opening the bridge to traffic two days early.
Major Project Elements