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Effects of size, species and adjacent lamina on moisture related strain in glulam

So Sun Lee, Sung Jun Pan, Gi Young Jeong


The goal of this study was to investigate the effects of size and species on moisture-related strain in glued–laminated timber (glulam). Swelling and shrinkage behaviors of different sizes (120 120, 180 180, and 180 240 mm2) of glulam made from larch and pine were measured using digital image correlation. A new approach to predict dimensional changes of glulam was developed by reflecting the nonlinear behavior of shrinkage based on MC change. It was compared with the existing method provided by the American Wood Council (AWC). Moisture-related strains of glulam were significantly influenced by size and species. Coefficients of swelling or shrinkage of glulam were determined to indicate statistical significance. When MC was changed from saturated condition to EMC of 12%, differences in dimensional changes in the width direction between experimental test and prediction results using the AWC method ranged from 87.7% to 260.0%. However, differences in dimensional changes in the width direction between experimental test and prediction results using the newly developed method ranged from 1.8% to 15.9%. Strains in the width direction of glulam could be affected by adjacent laminas along the glue line and the new approach could account for the effects. However, the AWC method could not reflect the effects of adjacent laminas along the glue line. Therefore, better prediction accuracy was achieved by using the new approach.


glulam, coefficient of moisture expansion, coefficient of moisture shrinkage, digital image correlation, strain

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