• Journal of the Korean Wood Science and Technology
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• v.40 no.2
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• pp.101-109
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• 2012

Wood composites are a hygroscopic material and have ability to exchange its moisture content with air. This study investigated the formaldehyde emission and moisture content change of four wood composites (particleboard (PB), medium density fiberboard (MDF), high density fiberboard (HDF), laminated HDF (L-HDF)) as a function of bake-out temperature and time. The composites were baked out for 1, 3, 5, 7, 10, 14, 21, and 28 days at temperatures of $20{\pm}2$, $35{\pm}2$, and $50{\pm}2^{\circ}C$ in a dry oven. The moisture content change was used to determine the emission bake-out of the composites. Best bake-out time results were obtained with after 7 days all composites. Formaldehyde emission values of composites decreased with decreasing moisture content for both temperatures. The formaldehyde emission results of bake-out temperature 35 and $50^{\circ}C$ showed a similar tendency.

• Journal of the Korea Furniture Society
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• v.25 no.2
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• pp.96-103
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• 2014

The objective of this study was to increase the utilizability of domestic thinning and small diameter wood as applying in pattern design which can be used in interior decoration, wood craft and wood furniture, and in developing the designs of furniture and household items. We investigated the physical and mechanical characteristics of Betula platyphylla Wood by pressurization and heat treatment. Color change is clear, and the wood density is increased with increasing pressing rate. The compressive strength, modulus of rupture and modulus of elasticity in bending strength are decreased as heating time is increased after pressing. However, shrinkage is improved after pressing and heating.

• International Journal of High-Rise Buildings
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• v.9 no.1
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• pp.87-93
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• 2020

Professionals who work in the realm of tall building design and construction are well aware that high-rises are the best solution for accommodating growing urban populations. Until recently, few would have thought to include tall wood buildings as part of that solution, but there is growing awareness that tall mass timber structures can help satisfy the need for density while addressing the need-equally urgent-for a more sustainable built environment. This paper examines the trend toward tall wood buildings in the United States, including their history and international influences, market drivers, structural performance, and economic viability, as well as building code changes that allow wood structures up to 18 stories. It highlights examples of mass timber projects, with an emphasis on benefits that impact return on investment.

• Journal of the Korean Wood Science and Technology
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• v.43 no.6
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• pp.868-875
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• 2015

In order to replace existing slit type steel plate on the wooden structure joint, the FRP-reinforced laminated plates were produced. Four types of FRP-reinforced laminated plates were produced according to the type of reinforcement and adhesive, and before applying to the joint, the adhesion performance test according to KSF 3021 and KSF 2160 and the Compact Tension (CT) type fracture toughness test specified in ASTM D5045-99 were carried out. As a result of adhesion performance test, all GFRP textile, GFRP sheet, and GFRP Textile-Sheet type FRP-reinforced laminated plates satisfied the requirement of soaking delamination percentage with smaller than 5% based on KS standard. However, aramid type specimen satisfied the standard as the soaking delamination percentage of 4.8% but it did not satisfied the standard as the water proof soaking delamination percentage of 70%. As a result of fracture toughness test, the volume ratio of reinforcement to timber became 23% so that the strength of FRP-reinforced laminated plates increased by two to four times in comparison to the control specimen. It was confirmed that the GFRP Textile-Sheet type specimen was most resistant to the fracture most since the ratio of stress intensity factor compared with that of the control increased to 61% owing to the parallel arrangement of glass fiber to the load. As a result of tensile shear strength test using FRP-reinforced laminated plates and nonmetal dowels, it is about 12% lower than metal connectors.

• Journal of the Korean Wood Science and Technology
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• v.45 no.4
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• pp.409-418
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• 2017

This work attempted to manufacture glued-laminated timber (Glulam) bonded with melamine-urea-formaldehyde (MUF) resin adhesives at various melamine contents from 20% to 50% under high frequency (HF) heating for a very short time. Two preparation methods were employed to prepare MUF resin adhesives with different melamine contents: one-batch method of synthesizing MUF resins in a single batch, and two-batch method of mixing urea-formaldehyde (UF) resin with melamine-formaldehyde (MF) resin that had been synthesized separately. As the melamine content increased, the gelation time and peak temperature of MUF resins decreased. The adhesion performance of plywood showed that the one-batch MUF resin adhesive with 50% melamine content only satisfied the standard requirement of water resistance. Thus, the one-batch MUF resin adhesive with 50% melamine content was applied for bonding wood lamina from four softwood species such as Japanese larch, Korean red pine, Korean pine and Japanese cedar to manufacture Glulam under HF heating. All Glulam samples bonded with the one-batch MUF resin adhesives with 50% melamine content except those from Korean Red Pine satisfied the requirement in water soaking or boiling water delamination test as an exterior grade Glulam. The presence of rosin in Korean Red Pine was believed to be responsible for its poor adhesion. These results showed that the one-batch MUF resin adhesives with 50% melamine content provided acceptable water resistance with exterior grade Glulam manufactured under HF heating.

• Journal of the Korean Wood Science and Technology
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• v.39 no.6
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• pp.521-530
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• 2011

Nowadays, market demand of structural Glulam is growing and diversifying. The durability of Glulam should be significantly considered when they are intended to apply for out-door use such as timber bridge and pergola. This study was aimed to develop the manufacturing process of preservative treated structural Glulam using domestic softwood species. 10 m long structural Glulam were manufactured from domestic pitch pine logs with CuAz-3 preservative treatment. At each manufacturing process, the production yield was evaluated. Finally, bending tests were performed to verify the structural performance of manufactured Glulam. From the results, it was shown that the preservative treatment process hardly influenced on the production yield. But domestic pitch pine was proved to not be suitable for making the preservative treated Glulam due to the large difference of preservative permeability between sapwood and heartwood.

• Journal of the Korean Wood Science and Technology
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• v.50 no.1
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• pp.1-11
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• 2022

To evaluate the bearing strength of red pine cross-laminated timber (CLT) with self-tapping screw (STS), which is widely used as a fastener for connection in CLT building, the bearing test was conducted. Accoring to the STS's diameters (8, 10, 12 mm), the bearing test specimens with half hole were manufactured. Bearing strength was compared and reviewed in consideration of the configuration in STS and the loading direction to the grain of red pine. As a result of the bearing test on the STS's diameter, the yield bearing load increases as the larger diameter of the STS in all directions of the red pine. The bearing strength of the thread part (thread + tip) was higher than the shank part (shank + shank cutter). In compared with the directions to the grain of red pine, the bearing strength of the cross section parallel to the loading direction was the highest, and the tangent section was the lowest bearing strength. The average bearing strength of the loading direction in parallel to the grain was 23.43 MPa, which was about 45% higher than the average 16.16 MPa in perpendicular to the grain. The predicted bearing strength calculated by Eurocode (EN) and Korean Building Code (KBC)'s equation was lower than the experimental value. It is nessesary to propose the new equations of bearing strength reflected the configuration information of STS.

• Journal of the Korean Wood Science and Technology
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• v.19 no.3
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• pp.35-44
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• 1991

In this study, thickness 40mm glulams were composed of thickness 5mm, 10mm Quercus laminas and Pinus koraiensis laminas to study on the effect of load variation on transition of neutral axis of laminated veneer lumber(LVL). The transition of neutral axis was examined by strain variation, which was checked by strain gauge. amplifier, recorder, and strain meter. The elasticity of glulam was estimated by E = $\Sigma(E_i\;I_ i)$/I and this estimated elasticity values were compared with the elasticity values of glulam in bending. The result obtained can be summarized as follows: 1. The location of neutral axis of glulam was effected by glulam composition methods 2. The neutral axis did not shift by load variation within proportional limit. 3. The estimated elasticity of glulam by E = $\Sigma(E_i\;I_ i)$/I showed much lower value than the elasticity of glulam in bending.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.3
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• pp.292-298
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• 2017

Numerical analysis for various design parameters should be preceded by optimal design of composite materials. Numerous studies have been conducted on the bolting of interconnecting beams. In this study, the response surface method was applied to optimize the design of bolted joints connected by laminated wood composite beams. The response surface was created by combining the FEA code for composite analysis and the algorithm for forming the response surface. Optimization on this response surface was performed with a genetic algorithm to derive the results. The determination of the optimum bolt-hole position for the connection of composite beams is an optimization problem. Tsai-Wu composite failure index, maximum deflection, and simple von Mises stress are set as the objective functions. It has been proved that the design results of the optimized bolt-hole are superior to the design performance of the existing conventional bolt-hole position.

• Journal of the Korean Wood Science and Technology
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• v.37 no.2
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• pp.128-136
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• 2009

Curved glued laminated timber (glulam) is rapidly coming into the domestic modern timber frame buildings and predominant in building construction. The radial stress is frequently occurred in curved beams and is a critical design parameter in curved glulam. Three models, Wilson equation, Exact solution and Approximation equation were introduced to determine the radial stress of curved glulam under pure bending condition. It is obvious that radial stress distribution between small radius and large radius was different due to slight change of neutral plane location to center line. If the beam design with extremely small radius, it should be considered to determine the exact location of maximum radial stress. The current standard KSF 3021 was reviewed and would be considered some adjustment determining the optimum radius in curved glulam. Current design principle is that the stress factor is given by the curvature term only in constant depth of the beam, but like tapered or small radius of beams, the stress factor by Wilson equation was underestimated. So current design formula should be considered to improvement for characterizing the radial stress factor under pure bending condition.