Use of engineered wood products, particularly structural glued laminated timber and/or cross-laminated timber (CLT), is indispensable for recent large-scale wooden buildings. Durability of adhesion of these materials is quite important for assurance of reliable mechanical properties throughout their service life. Therefore, only some highly reliable adhesives are permitted for use. Resorcinol resin adhesive has been used for a long time as a load-bearing structural wood adhesive. In addition, new structural adhesives such as the aqueous polymer-isocyanate adhesive developed in Japan and one-component polyurethane adhesives for structural use developed in Europe have recently been initiated for use in structural glued laminated timber and CLT. These isocyanate-based resin adhesives are different from resorcinol resin in terms of their chemical structure and physical performance. Therefore, the requirement of bond qualities of structural wood adhesives has been reconsidered, and standards have also been maintained in each country. Here the present standards for structural wood adhesives and evaluation methods for their bond performance are reviewed.

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This study examined the effects of the quantity of knots present in interior paneled walls of softwood through a preference evaluation. In this study, psychological evaluations were applied based on the ideas of cognitive psychology, such as the context effect, in which human perception not only depends on the object itself, but is also strongly influenced by the scene and the situation that surround the objects. To examine the ratio of knot area to panel area (KA/PA), the quantity of knots in the wall panels was set to four levels ranging from 0% to 1.32%. The scene chosen for subject evaluation was the living room of a residence. Photographs of four living rooms, each with different colored wallpaper and furniture arrangement were combined with the aforementioned wainscot wall panels. The preference evaluation of the four living rooms showed a decrease in subject preference with an increase of KA/PA. The rate of decrease in preference was slight in the range of 0-0.86%, but this rate then changed significantly at 1.32% with the increase of KA/PA. However, more than half of the subjects stated positive preferences that were within the range of 0.86% by that they either “like it” or “like it a little”. The significance of the difference was checked statistically with the use of two-factor analysis of variance (ANOVA). The effect of KA/PA was evident while no significant difference was observed by the effect of room type and interaction. The results suggested that the subjects of the study prioritized the context of a residential living room over the impression of each living room.

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