• Journal of the Korean Wood Science and Technology
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• v.45 no.3
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• pp.243-249
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• 2017

This study was performed to find out the optimum adhesive conditions on manufacturing a cross-laminated timber (hereinafter CLT) with using domestic Korean Pine (Pinus koraiensis). The adhesive conditions including a applied amount of the glue and a Pressure are the one of the most important key factors on establishing CLT production process. The shear strength was examined with differing the adhesive conditions while using Phenol Resorcinol Formaldehyde Resin Adhesive (PRF resin). The optimum adhesive conditions was confirmed to be: glue spread of $250g/m^2$ and Pressure of 0.8 MPa respectively. The grain directions of glued specimens were also considered, perpendicularly bonded and parallelly bonded groups. Shear strength of the former group showed lower values than the latter group which is considered to be the effect of a rolling shear. Meanwhile the shear strength of both group satisfied the Korean Standard (KS F 3021) and the European Standard (EN 14080 and EN 16351). The results derived from this study can be used as the basic data for manufacturing the CLT with domestic Korean Pine. And additional researches for the other species including domestic Korean Larch and Pitch Pine is also now being performed.

• Journal of the Korean Wood Science and Technology
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• v.33 no.1 s.129
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• pp.87-96
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• 2005

This study was carried out to evaluate the shear bond strength and adhesive bond durability of structural glued laminated timber (glulam) manufactured with mixed species lumber of Korean red pine, Korean pine and Japanese larch, using resorcinol adhesive and water-based polymeric-isocyanate adhesive (WPI). Each board used as a glulam lamina was graded by visual inspection. The visual lumber grade of the all species was very low due to the large size and number of knots and the steep slope of grain. In view of the results, appropriate pruning, sawing and drying processes might be needed to produce high grade lamina lumber with small knot size and drying defect free. Shear bond strength of every tested glulam specimen ranged between 7.9 and $9.9N/mm^2$, and much higher than the Korean Standard (KS) for glulam shear bond strength, $7.1N/mm^2$. There was not much shear bond strength difference between wood/resorcinol and wood/WPI. The resorcinol adhesive bond durability exceeded KS requirements. However, delamination on the end-grain surfaces of WPI glulam submerged in both room temperature and boiling water severely occurred, and its durability did not meet KS requirements. Further investigations may be required, and special care should be taken, to ensure long service life of WPI glulam used for exterior application. Results of this study are expected to be useful for improvement of mechanical properties and structural performance of mixed species glulam.

• Journal of the Korean Wood Science and Technology
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• v.46 no.3
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• pp.213-220
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• 2018

In order to use Pitch pine (Pinus rigida Miller) as the material of the structural glued laminated timber, the effect of the amount of resin exudation due to storage time after the planning and the knot of the lamina were evaluated on the bonding properties of the glued board with resorcinol resin. For Pitch pine that was dried at high temperature ($120{\sim}95^{\circ}C$) and low temperature ($65{\sim}50^{\circ}C$), the flat sawn(tangential section) showed higher amount of resin exudation than the quarter sawn(radial section). And the low temperature drying wood showed higher resin exudation than the high temperature drying wood. The low and high temperature drying wood showed the highest amount of resin exudation on the 3rd day and 7th day, respectively and they were gradually decreased. However, there were no significant differences from 15 to 90 days. Adhesion performances were low until 2~3 days with high exudation of resin, but there were no significant differences after 15 days. Both high temperature and low temperature drying woods satisfied the Korean standard regardless of the storage time. The adhesive strengths of the laminating parts including knots were higher than those of KS criteria, but the wood failures were not satisfied the KS standard. Adhesive performances according to the laminating combinations (quarter sawn + quarter sawn, flat sawn + flat sawn, quarter sawn + flat sawn) were better than those of KS criteria in all laminating combinations in both high temperature and low temperature drying woods.

• Journal of the Korean Wood Science and Technology
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• v.43 no.4
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• pp.446-455
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• 2015

Based on comparative studies on standards and grading procedures of machine graded lumber in Korea and other countries, this study proposed a procedure of determining the grade classification and design strengths of domestic machine graded lumber. Differences between machine stress rated lumber and E-rated laminations were detailed in order to clarify the need for the procedure improvement. To this improvement the use of average MOE requirement for grading was introduced instead of the fixed minimum MOE requirement which is currently used in the Korean standards. It was found that the fixed minimum MOE requirement method was easier for an inspector to grade but, less efficient as a strength predictor than the average MOE requirement method. The advantage of average MOE requirement method is statistically MOR-MOE regression-based MOR prediction and highly efficient in quality control though it requires a computer-aided operation system in an initial setup. A major weakness of the current Korean grading system was found that different strength characteristics depending on wood species were not reflected on the grade classification and the tabulated allowable design stress. The proposed procedures were developed taking advantages of respective merits of both methods and based on MOR-MOE regression analysis. Through this procedure, the grades of machine stress rated lumber should be revised to become interchangeable with E-rated lamination, which would be beneficial to the cost competitiveness of domestic machine graded lumber and glued laminated timber industry.