Glued laminated timber

The adhesives to be used in making joints between timber members are specified in BS 5268 Part 2 (24). Permissible adhesive types based on the exposure conditions of the joint are reproduced here as Table 7.4. Weather and Boil Proof (WBP) products such as resorcinol and phenol-formaldehyde are stipulated in damp conditions whereas melamine and urea-formaldehyde adhesives are permitted in permanently dry situations. Natural adhesives such as casein are now only allowed in the least hostile exposure category. 

One particular structural application of adhesives is in the manufacture of glued laminated timber or glulam members. This is normally manufactured by glueing together at least four planks of timber with their grain essentially parallel. The laminations are usually machined from 38 or 50 mm thick timber although thinner sections may be necessary in the production of curved members. End 

Exposure Category Typical exposure conditions Adhesive type BS reference 

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Glued-laminated timber (glulam) is an engineered stress-rated produet that eonsists of two or more layers of timber in whieh the grain of all layers is oriented parallel to the length of the timber. 

Various countries have standard practices established to determine allowable properties for glued-laminated timber. In the United States, ASTM D3737 (ASTM, 2005g) guides the allowable stress development. 

AITC (1990) Standard for preservative treatment of structural glued-laminated timber. AITC 109. American Institute of Timber Construction, Englewood, Colorado AITC (2001) Standard appearance grades for structural glued-laminated timber. AITC 110. 

Anonymous (1996) Best Management Practices for the Use of Treated Wood in Aquatic Environments. USA version. Western Wood Preservers Institute, Vancouver, BC ANSI/AITC (2002) Structural glued laminated timber. ANSEAITC A190-1. American National Standards Institute and American Institute of Timber Construction, Englewood, Colorado... 

CEN/TC 124 Timber Structures , SN EN 408 2003 Timber structures — construction timber and glued laminated timber — Determination of some physical and mechanical properties, SIA Schweizerischer Ingenieur- und Architektenverein Zurich, Switzerland (2003). 

On their own, adhesives have been used as an attempt to repair minor delamination of glued laminated timber or drying fissures (Fig. 2). Besides safety considerations, fissures and delamination may contribute to increased risk of biological attack, therefore, it may be advisable to have them sealed for the sake of durability. 

Useful mono-material structural elements may be formed by bonding together a number of individual pieces of the same material. Glued laminated timber (glulam) members as described in Chapter 7 represent a development in which structural elements of large cross-section may be created. Adhesive bonding, as opposed to mechanical fastening, leads to reduced stress concentrations as well as the elimination of joint slip. The same principle may be applied to other materials where appropriate, such as aluminium extrusions and... 

Correction of fissures and delamination in glued-laminated timber beams (Fig. 22.6(a)). 

EN 386 Glued laminated timber. Performance requirements and minimum production requirements. 

EN 390 Glued laminated timber. Sizes. Permissible deviations. 

EN 14080 Timber structures. Glued laminated timber. Requirements. EN 14374 Timber structures. Structural laminated veneer lumber (LVL). Requirements. 

ASTM D7199 Standard practice for establishing characteristic values for reinforced glued laminated timber (glulam) beams using mechanics-based models. 

EN 391 Glued laminated timber. Delamination test of glue lines. 

EN 408 Timber structures. Structural timber and glued laminated timber. Determination of some physical and mechanical properties. 

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