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Foundations, Framing, Sheathing, and Vapor Barriers
Published in Kathleen Hess-Kosa, Building Materials, 2017
Glued-laminated timber, often referred to as glulam, is a timber product manufactured from dimensional lumber—typically 2-inches thick, custom widths up to 14½ inches. The lumber stock is joined together end-to-end and glued together to almost unlimited depths and lengths—straight and curved, treated and untreated. According to one manufacturer: Glulam is available in several species of wood including southern pine, Douglas fir, Port Orford cedar, and Alaskan yellow cedar. Southern pine species can be preservative pressure treated prior to gluing, which unlike treatment after gluing, allows the treatment to reach the center of the beam for additional weather resistance. Port Orford cedar and Alaskan cedar are naturally decay resistant and therefore don't require preservative treatment. Douglas fir is the exception in glulam. Doug fir cannot be preservative treated without incising (a process that scars the beam with thousands of slit-like holes in the surface), nor is it naturally decay resistant. Topical treatments are available, but not nearly as effective as pressure treatments. (Timber Systems 2015)
Vaulted structures in history and modern structural solutions
Published in Pere Roca, Paulo B. Lourenço, Angelo Gaetani, Historic Construction and Conservation, 2019
Pere Roca, Paulo B. Lourenço, Angelo Gaetani
Glued laminated timber, also called glulam, is a type of structural engineered wood product comprising several layers of dimensioned lumber bonded together with durable and moisture-resistant structural adhesives. Accordingly, a single large structural member is manufactured from smaller laminated pieces of lumber, shaped in different forms for elements such as vertical columns, horizontal beams or curved arch shapes. In this way, glulam provides the strength and versatility of large wood members without relying on the old growth-dependent solid-sawn timbers. This provides a more homogeneous material and also reduces the overall amount of wood used when compared with solid sawn timbers by diminishing the negative impact of knots and other defects.
Woods
Published in M. Rashad Islam, Civil Engineering Materials, 2020
Glued laminated timber (glulam) is composed of several layers of dimensional lumbers glued together with moisture-resistant adhesives, as shown in Figure 10.17. The combined section is a large, strong, structural member that can be used as columns, beams, or in curved shapes with extensive design flexibility. The grain of all laminations is approximately parallel longitudinally. The separate lamination should not exceed 2 in. in net thickness. NDS-S (2018) lists the standard specifications for the dimension of glulam sections, the reference design strengths, and other information.
Knots and their effect on the tensile strength of lumber: A case study
Published in Journal of Quality Technology, 2023
Shuxian Fan, Samuel W. K. Wong, James V. Zidek
As practical implications of this study, our proof-of-concept shows that more extensive testing and efficient scanning techniques would be desirable to produce larger samples representing more diverse lumber populations (e.g., different species and dimensional sizes). In particular, an interesting extension would be to take multiple strength measurements on a single specimen, to better understand how strength varies along a piece of lumber. We note that even modest gains in strength prediction accuracy would be worthwhile, with the large volumes of lumber being produced worldwide and the increasing popularity of wood as a sustainable building material. More accurate predictions could in turn reduce the within-grade strength variation, via updates to the rules used to classify lumber into grades. This would be beneficial for both manufacturers and consumers of lumber, in terms of extracting better value from harvested trees and meeting strength requirements for intended uses with greater confidence. Overall, the model and approach presented could lead to a more refined way of managing the quality of manufactured lumber. Beyond individual specimens, another application of this modeling approach is in estimating the strength of larger engineered wood products (or “mass timber”) where lumber is the primary feedstock (see Yard 2017, for more information). An example of this is glued laminated timber (glulam) where individual pieces of lumber are glued together so that they resist the applied load in a parallel fashion. The higher load carrying capacities of glulam allows wood to be used in taller and larger buildings. In glulam, it is unlikely that the weak cell of one lamination aligns with the weak cell of the adjacent lamination (Issa and Kmeid 2005). The ability to estimate the strength and variability of glulam without extensive full-size testing of all sizes and grades of large glulam would be an important step toward establishing design values for this product.