Abstract
With intensified use of timber beams, consisting of laminations of relatively thin boards and planks glued together, the problem of glue lines coming apart under changing conditions of moisture content in the timber has become of considerable importance. From an examination of glued timbers undergoing changes in moisture content, it appears that delamination, when it occurs, most frequently does so when the moisture content is being reduced; during such a dehydrating phase not only does shrinking take place but also checking of the wood. Results of experimentation and field trials indicate that thin laminations are better than thick ones for gluing, and wood species with low moduli are better than species with high moduli. Adhesives must be employed which have high shearing strength and high tensile strength perpendicular to the glue line if laminated beams are to be dependable in service.
