Photo: APA
The popularity of glulam beams has skyrocketed during the past decade, particularly in the hospitality, religious, and education sectors, where appearance, sustainability, and long spans are often desired.
But working with glulams can be tricky, especially for AEC professionals who are unfamiliar with the material.
We asked Archie Landreman, technical director with WoodWorks, an educational initiative for nonresidential wood construction, to identify key considerations for specifying and installing glulams. He offers the following tips:
Customize for loads and spans. To minimize costs, make sure to specify glulam products based on the load and span requirements of the project. For example, glulam beams with high structural properties should not be used on projects with light loads and short spans.Don't miss the layup. Determine whether a balanced or unbalanced layup is required. An unbalanced layup has higher-strength laminations positioned on the tension side of the member and is typically used for simple-span beam applications. A balanced beam has equal grade laminations on the top and bottom of the beam and is typically used for cantilever and continuous-span conditions.Determine the camber factor. Camber is an initial curvature built into a fabricated member. It is a consideration for long spans because it provides the flexibility to negate possible effects of long-term deflection or creep. Most stock beams are supplied with little or no camber so that they can be easily framed in typical residential applications.Grade your appearance. Where appearance of the glulam members is a design consideration, an appearance grade must be specified. The four industry appearance classifications are framing, industrial, architectural, and premium, with premium having the highest level of finish.Specify the proper stress class. One of the first specification requirements considered should be the stress class of the glulam member. To simplify the process, seven different stress combinations covering virtually any end-use requirement are tabulated in the 2005 National Design Specification for Wood Construction.Plan for exposure. Where glulam beams will be exposed to weather, request a preservative-treated product or consider wood that has a natural resistance to decay, such as Alaska yellow cedar or Port Orford cedar.Handle with care. Proper storage and handling are necessary in order to protect glulam beams prior to installation. Make sure the beams are individually wrapped and sealed and elevated above ground during storage to avoid unnecessary moisture absorption.Be careful when cutting, notching, or drilling. Cutting, notching, or drilling a beam may seriously affect its ability to carry the design load. If this is necessary, make sure to consult with an engineer. Also, reference APA's Field Notching and Drilling of Glued Laminated Timber Beams.
For more on glulams, visitwww.woodworks.org.
