FEATURED PROJECT: Sellwood Bridge

The 1,971-ft ‘old bridge,’ originally constructed in 1925, was a marvel of engineering for its time; largely because of its 1,100-ft long “fixed-span” over the Willamette River. The bridge was originally designed to be a local community connector, not the primary connector it ended up being with over 30,000 cars driving over it each day. In 2005, after receiving a sufficiency rating of (2) out of (100) from the National Bridge Inventory, Multnomah County understood that replacing bridge was required and began setting the project in motion. By the time a design was completed, a GCCM was selected, and TMF started receiving steel for the new bridge in the Spring of 2013, the old bridge was nearly 90.

Thompson’s scope of supply included the fabrication of all major bridge components: Arches, Arch Cross-Frames, Vertical Spandrels and the Bridge Deck Steel. 5,000-Tons in total. The distinctive feature of the bridge is the (3) sets of arches which cover 1,275 feet of the 1,976 ft crossing. Each arch was fabricated in segments, with each segment over 100’ long. The arches, cross-frames and spandrels are a ‘box-style’ fabrication with internal diaphragms. The project required full pen welding along all box joints and all internal diaphragm joints, and as a result, required continuous heating to mitigate distortion control.

The original design featured a fabrication tolerance of zero, which required precision and forethought on TMF’s behalf given the extensive constricted welding and myriad of bolted connections throughout the project. In lieu of a coating system for this project, Weathering Steel was used instead. The ‘organic’ look to the bridge matches its surroundings and the communities it connects.