2015 Broadway Bridge Repair
CM/GC [Construction Manager/General Contractor delivery method]
This project replaced the Rall wheels and tracks on the historic, 100-year-old Broadway Bridge in Portland, Oregon. There were only five Rall bascule bridges ever built and each was uniquely different. The Broadway Bridge has an unusual way of operating. When the bridge opens, in addition to each leaf rotating up and away from the river channel, they also roll back on the Rall wheels. This allows for more clearance in the River Channel so that larger ships can pass through the bridge.
The original engineer’s intent, over 100 years ago, was to switch out the Rall wheels after 40-50 years. This was never completed because there was no historical data left from the original engineer to show how this was to be accomplished. Hamilton worked hand-in-hand with the owner (Multnomah County) and the A/E firm to develop means and methods, specifications, and permit applications for the complex process of fabrication and replacement of the mechanical components.
To replace the Rall wheels Hamilton jacked each 4.5-million-pound leaf up just enough to get the wheels off of the track, and then used a large barge mounted crane to remove and replace the wheels and tracks. Each of the four Rall wheels weighed 88,000 lbs., four trunnion shafts weighed 7,500 lbs. each, and four sets of tracks weighed approximately 38,000 lbs. After the wheels were replaced Hamilton made adjustments to mechanical components on the bridge to ensure the new Rall wheels were properly aligned to roll straight back and straight forward when the bridge opened and closed.
As challenges were encountered, Hamilton developed innovative solutions. When the unique design of the structure provided only one point in which the structure could bear the heavy load while being jacked, Hamilton reinforced the existing gusset to bear double the load. When a trunnion shaft seized in the collars due to damage incurred during the original construction, Hamilton’s solution was to freeze the inside of the 7,000 lb. shaft with liquid nitrogen and heat the collar simultaneously. Hamilton’s approach and creative problem solving enabled operations to be maintained and an accelerated schedule to be implemented.
The integrated team collaborated during the design phase and leveraged Hamilton’s knowledge of construction to maximize innovation, resulting in an economical and constructible solution. A value-based early work package facilitated delivery of the new Rall wheel and track components several weeks prior to a United States Coast Guard (USCG) closure and saved 12 months off the project schedule.
Hamilton’s project management allowed for 99% of commuter traffic (Portland Streetcar and vehicular traffic) to be maintained. Keeping one bascule leaf operational allowed for 100% river traffic to be maintained. Providing protective platforms in the work areas allowed for 100% of pedestrian/bicycle traffic to be maintained.
Major Project Elements