Home » News » Pedestrian bridge slides in under LRT crossing near Portland, OR

Pedestrian bridge slides in under LRT crossing near Portland, OR

September 17, 2015


A 234' Big R Pedestrian Bridge is maintaining a low profile these days under the new TRIMET Light Rail Bridge in Milwaukie, Oregon. Our sleek, Modified Bowstring Truss design recently side-slipped into place, all in one piece from a specially-made, temporary work platform over the Willamette River. Talk about an exact fit!

Low-profile, low-maintenance
In fact, with it’s long-lasting Fiber Reinforced Polymer (FRP) composite decking and Weathering Steel finish, it will undoubtedly still be hanging in there for many decades to come — as it will also be maintaining a low profile on the maintenance roster.

Using lightweight FRP decking panels was key
Due to the side-slip installation method and the load requirements of the LRT bridge, using lightweight FRP composite decking panels was key in keeping the weight down, while offering a full suite of compelling advantages: 

  • Light weight: As little as 25% of the weight of concrete and 50% of wood.
  • Corrosion resistant: Important in cold climates and coastal areas.
  • High strength: Composite decking provides high strength with very high safety factors.
  • Quick installation time: No formwork, curing times and possible weather delays.
  • Lower life cycle costs: Long-lasting, zero-maintenance material adds up to significant savings over the 75-100 year life of the bridge.
Temporary work platform     
Lightweight FRP Decking

The benefits of Naturally Weathering Steel

Weathering Steel contains elements that allow it to form a protective coating or patina when properly exposed to the atmosphere. This offers several benefits:

  • Reduced toxic emissions: No oil-based coating is used, which reduces emissions of volatile organic compounds.
  • No contaminated blast debris in habitats: Because the steel is not painted, no periodic maintenance blasting is required.
  • Cost savings of 10% or more initially and even more over the life of the structure: No painting and steel’s durability mean reduced costs.
  • Long life and high performance: Weathering Steel has been used on bridges for many decades and performs well in most environments.

Big R Bridge is proud to have been selected to participate in this portion of the large-scale TRIMET Light Rail Design/Build expansion project, known as the PMLR Transit project – West Segment.     

Project at a glance:

Name: Kellogg Lake Pedestrian Bridge
Location: Milwaukie, Oregon (near Portland)
Owner: TRIMET Light Rail   
Design/Build Consultant: David Evans & Associates, Inc. 
Contractor: Stacy and Witbeck, Inc.  
Product: Long-Span Pedestrian bridge (Modified Bowstring Truss)
Application: River Crossing
Dimensions: Span 234' x Width 12.3' x Truss Height 13'