Outdoor Exposure Test for Sugi Glued-Laminated Timber Manufactured Using 7 Adhesive Resins I.

Shear strength and wood failure ratio

Abstract

Five-ply sugi (Cryptomeria japonica D.Don) glued-laminated timbers were manufactured using three resorcinol resin adhesives, three aqueous polymer-isocyanate resin adhesives, and a vinyl acetate-based resin emulsion adhesive (VAE). They were impregnated with wood-preservative (ACQ), and exposed under outdoor conditions with their glue-layers at level position for ten years. Block-shear tests were conducted after 1, 3, 5, and 10 years of exposure. After 10 years of exposure, significant differences were recognized for shear-strength among adhesive resins as the result of analysis of coefficient variance (AOCV). Results for pair-comparison of AOCV between adhesive resins, showed significant differences in 4 pair-comparisons and those included VAE. Standard deviations of shear-strength tend to increase with exposure year, and for VAE they were larger than for the others. Results of goodness-of-fit tests of shear-strength for normal, log-normal, 2P-Weibull, and 3P-Weibull distributions, showed that none of these forms fit VAE after 1 year of exposure. Wood-failure ratio decreased gradually with exposure duration ; however, even after 10 years of exposure, it was more than 80% regardless of adhesive resin.