Peaked and Cambered Glulams

Building designers are offered creative ways in which to utilize Glulam in the construction of their buildings. Glulams have been popular over the years because of their versatility in timber construction and because of their aesthetic appeal. The use of Peaked and Cambered Glulams (also known as Pitched and Tapered) is one way to achieve a desirable clear span while creating the feeling of extra spaciousness. These beams are identifiable because their tops are pitched to form the roof slope and the bottoms are curved. They are ideal in the construction of gymnasiums, religious structures, park shelters, horse arenas, and many other building types.

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These Peaked and cambered Glulams were used in the construction of a Horse Arena in Yelm, Washington. They span 80′ and measure 15′-4″ in width. To facilitate shipping WWS designed them with detachable haunches.

 A number of Peaked and Cambered Glulam beams manufactured of Douglas fir have failed over the years as evidenced by separation or “cracking” following the central curved section of the beam. These failures, known as radial tension failures, are attributed mostly to low radial tension strength in Douglas fir. This radial tension phenomenon was not discovered until the late 1960’s.

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These beams used in the construction of a horse barn in Sherwood, Oregon display a classic radial tension failure.

 A revised design method was first published in the AITC Construction manual in 1974 and didn’t show up in the Uniform building code until 1976. Therefore, any Peaked and Cambered Glulams manufactured prior to 1976 should be considered unreinforced unless inspection proves otherwise. Simplified design procedures for these beams can be found in the AITC Construction manual.

In recent years, many building owners, contractors, and engineers have called Western Wood Structures to report radial tension failures and to ask for a permanent engineered remedy. These calls often lead to a site inspection by a licensed WWS engineer and a structural analysis which is used to determine the appropriate solution. The solution almost always consists of the installation of shear dowels (rebars in epoxy-filled holes or fully threaded lags). In some instances these beams require strengthening by the addition of new laminations or by the installation of a post tension system.

Below are some examples of Peaked and Cambered Glulams we have repaired and brought up to current building code requirements.

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These beams over  the cafeteria at Tigard High School in Tigard, Oregon (above) were repaired and code upgraded by installing shear dowels and by adding a post tensioning system. The shear dowels were installed from the under side of the beams.

 

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These beams in the Cultural Hall of the LDS Stake Center in Juneau, Alaska were repaired by installing shear dowels in epoxy-filled holes. The dowels were installed from the tops of the Glulams so a temporary tent was constructed in order to maintain warm temperatures to allow the epoxy to cure properly.

 

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These Glulams in the Pend School in Kootenai, Idaho were repaired and code upgraded by the installation of shear dowels, the application of additional laminations, and by installing a post tensioning system.

 

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These beams over the sanctuary of the Spokane Friends Church were upgraded by the installation of shear dowels and added laminations. Refinishing is usually required due to the use of paste epoxy on the outside of the beams.