Lewis Bolt: Wednesday's Word Of The Week

A Lewis Bolt (more specifically, the Lewis Evertite System) is a specialized piece of hardware used in bridge construction. Solid glulam panels (basically large beams laid on their side) make an effective road structure, similar to concrete planks. They can span parallel to the roadway as a simple bridge for short spans. For longer bridges, transverse panels are attached across a series of bridge stringers which can be glulam or steel.

Lewis bolts are used to attach glulam bridge panels to steel stringers. They consist of four parts:

• A bolt with with a large dome head, similar to a carriage bolt
• A shoe with a step that matches the steel beam flange thickness (top of shoe has teeth which engage the bottom of glulam panel, the lower portion of shoe grips the bottom of steel flange.)
• A spring (so that bolt will stay tight even as the glulam panel thickness varies with moisture content)
• A nut

*Wednesday's Word Of The Week is a feature on Unalam's Wood Times Blog. Each Wednesday our structural engineer, Rik Vandermeulen, will discuss a new term associated with glulam manufacturing. He will do this until we run out of words. If there is a timber or glulam term that you have heard of and want to know more about, let us know in the comments.