Gothic Arch – Wednesday’s Word Of The Week
A new type of structural element this week is the arch. Glulam arches are pairs of glulam members that lean against each other to create an open span beneath. Because they are leaning against each other, there is a horizontal “thrust” force at their bases which must be resisted by the supporting foundation – usually by tying the arch bases together across the foundation.
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| Gothic arches |
There are many different arch shapes possible with glulam – the first is the Gothic arch. A pure Gothic arch consists of two halves, of constant radius R, and their bases separated by R. To create a 60′ span, use 60′ radius arches. That profile is quite steep for most buildings, so it is typically altered but maintains:
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arch member is constant depth,
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curved portion is constant radius,
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may or may not have a straight portion near the peak,
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there is always a ridge at the peak (never flat at the top like a semicircle.)
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| Historical brochure showing uses for Gothic arches (barn rafters) |
Gothic arches are most frequently used in barns (or buildings intended to resemble barns) and simple storage buildings. They are usually produced from combination 24F-V5 southern yellow pine.
*Wednesday’s Word Of The Week is a new 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.