Project Description

Standing 145 feet above the Koksilah River, the Kinsol Trestle is one of the tallest free-standing and most spectacular timber rail trestle structures in the world. This historic trestle was completed in 1920 as part of the Canadian Northern Railway; however, the rail route was retired in 1979.

As a basis for restoration planning, Cascade Engineering (now part of ISL) analyzed data using RISA 3-D and conducted a full physical inspection of the trestle that included over 400 wood-bore samples. Restoration work included the replacement of unsound timbers, minor refurbishment of a Howe Truss substructure and rebuilding of 17 structural piers to support the new 614-foot walkway atop the structure.

Construction of the bridge incorporated concrete footings, six Howe trusses and more than 1.2 million board feet of timber—all of it second growth BCgrown Douglas-fir and cypress. The project has been recognized with several awards for its dedication to sustainability since the rehabilitated bridge retains 60 per cent of its historic timber.

Challenges

• Coming up with a viable solution to save the bridge
• Designing the bridge substructure to resist wind and seismic loads
• Integrating new with old in designing the wood connections

Solutions

• Expert advice enabled the owner to justify keeping the bridge
• Careful analysis enabled the bridge code requirements to be met
• Care was taken in selecting the materials and designing the connections so they matched the original structure