Impact of Cyclic Moisture on Shrinkage of Glue-Laminated Softwood
Joan Mary Jojo1 Jins Jushu2 Suryakiran S3 Surya R4
1 Assistant Professor, Dept of Civil Engineering, St Thomas College of Engineering & Technology, Chengannur, Allepey, Kerala
2,3,4 UG Student, Dept of Civil Engineering, St Thomas College of Engineering & Technology, Chengannur, Allepey, Kerala
1 joan@stthomascollege.ac.in, 2 jinsjushu@gmail.com
Abstract. Glulam softwood, widely used in construction due to its strength-to-weight ratio and sustainability, undergoes dimensional changes under varying moisture conditions. Cyclic moisture exposure accelerates these changes, potentially affecting its long-term performance. This study investigates the impact of cyclic moisture exposure on the shrinkage behaviour of glue-laminated (glulam) softwood, which affects structural integrity and dimensional stability in engineered wood products. The experimental methodology involves fabricating glulam specimens using industry-standard adhesives and softwood laminations. Samples are subjected to controlled cyclic moisture conditions, alternating between wetting (85% relative humidity) and drying (30% relative humidity) in a controlled environmental chamber. Shrinkage strains are measured periodically. The testing duration spans up to 20 cycles, simulating natural seasonal variations. Preliminary results indicate that cyclic moisture exposure exacerbates anisotropic shrinkage, with tangential shrinkage being up to three times higher than radial shrinkage. This study aims to validate these findings while examining the influence of adhesive type and lamination orientation on shrinkage rates. The results are expected to provide a quantitative relationship between cyclic moisture levels and shrinkage behavior, offering insights for optimizing glulam manufacturing and service life prediction models. This research contributes to improving the resilience and sustainability of wood-based materials in modern construction practices. Unlike prior studies that focused on individual softwood specimens, this research investigates glulam as a structural composite, considering adhesive effects and lamination orientation under cyclic moisture exposure
Keywords: Glulam, Cyclic humidity, Dimensional Change Coefficient, Fibre Saturation point, Timber structures
