BNSF Trunnion & Bearing Replacement

Owner: Burlington Northern Santa Fe

Seattle, WA
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October 2009 - December 2011
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Project Details

Salmon Bay is the waterway connecting the Puget Sound to Lake Washington near Seattle. BNSF has two tracks that run on their bascule bridge that services 50-60 trains daily. Built in 1913, the bridge had many service delays due to improper seating, warranting repairs to the trunnion pin and bearings.

Advanced American Construction was contracted with BNSF to put together a work plan to implement a jacking system to lift the 3 million pound counterweight. AAC with Smith Monroe & Gray, Inc. was able to value engineer the original jacking system to provide a more efficient and safe jacking system. The new system also allowed AAC to be better prepared for a upcoming lock outage.

The challenge of installing all the temporary jacking steel while not delaying any trains, and maintaining marine traffic began in 2010. With no direct access to the work, coordination with BNSF was key as AAC used the live train tracks to deliver all 220,000 pounds of temporary steel out to the bridge.

BNSF requested to the Coast Guard that the bridge be in the down and locked position while the bearings were replaced. This gave AAC a limited amount of time to replace one bearing at a time. During the lock outage AAC jacked the 3 million pound counterweight to relieve the weight, remove pins and bearings, and replace with new 22,000 pound spherical bearings along with a 20 ½-inch diameter pins.

64,000 pounds of new structural steel walkways and platforms were installed to put the finishing touches on this challenging and successful project.

Project Highlights

  • Remove two existing trunnion bearings and shafts and replace with spherical bearings, field align bore truss ears, and install larger diameter shafts
  • Installation of 220,000 pounds of temporary steel for jacking operations
  • Critical lift of approximately 3,070 kips
  • Replacement of bearing assemblies occured during 14-day marine lock outage
  • Install new structural steel access platforms and stairs

Project Photos