• Journal of the Korean Wood Science and Technology
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• 제39권2호
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• pp.179-186
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• 2011

In an effort to understand the hydrolytic degradation process of cured urea-formaldehyde (UF) resins responsible for the formaldehyde emission of wood-based composite panels, this study analyzed the influence of acid hydrolysis on the morphology of cured UF resins with different formaldehyde/urea (F/U) mole ratios such as 1.6, 1.4, 1.2 and 1.0. Field emission-scanning electron microscopy (FE-SEM) was employed to observe both exterior and fracture surfaces on thin films of cured UF resins before and after the etching with hydrochloric acid as a simulation of the hydrolytic degradation process. FE-SEM images showed that the exterior surface of cured UF resin with the F/U mole ratio of 1.0 had spherical structures after the acid hydrolysis while the other cured UF resins were not the case. However, the fracture surface observation showed that all the samples possessed spherical structures in the cured state of UF resins although their occurrence and size decreased as the F/U mole ratio increased. For the first time, we found the spherical structures in cured UF resins of higher F/U mole ratio of 1.4. After the acid hydrolysis, the spherical structures became a much predominant at the fracture surface. These results indicated that the spherical structures in cured UF resinswere much more resistant to the hydrolytic degradation by the acid than amorphous region.

• 한국환경농학회지
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• 제28권4호
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• pp.340-346
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• 2009

Chromated copper arsenate (CCA) is a chemical wood preservative that has been intensively used to protect wood from decay during the last few decades. CCA is widely used to build structures such as decks, fences, playgrounds and boardwalks. However, structures constructed of CCA-treated wood have caused adverse environmental effects due to leaching of Cr, Cu and As into surrounding soils. This research was conducted to monitor the vertical and horizontal distribution of Cr, Cu and As in soils adjacent to CCA-treated wood structures in Korea. Two structures constructed with CCA-treated wood were selected at Hongcheon and Chuncheon in Gangwon Province, South Korea. Eleven soil profile samples were collected at depths of 0 to 80 cm at each site, while 12 surface soil samples were collected at distances of 0 to 200 cm from each structure. The soil chemical properties, soil particle size distribution and total metal concentrations were then determined. The results revealed that soils near CCA-treated wood structures were generally contaminated with Cr, Cu and As when compared to the background concentration of each metal. In addition, the concentrations of Cr, Cu and As in soils decreased as the vertical and horizontal distance from the structure increased. Further studies should be conducted to evaluate the mobility and distribution of these metals in the environment as well as to develop novel technologies for remediation of CCA contaminated soils.

• Structural Engineering and Mechanics
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• 제31권3호
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• pp.315-331
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• 2009

Mechanical connections are recognized as extremely important elements in the aspect of strength and structural safety. However, classical structural model does not consider the connection stiffness properties, and are based on models with pinned or rigid joints only. In fact, mechanical connections are deformable and behave not linearly, affecting the whole structure and inducing nonlinear behavior as well. The quantification of this effect, however, depends on the description of the working of the connectors and the wood response under embedment. The theoretical modeling of wood structures with semi-rigid connections involves not only the structural analysis, but also the modeling of both single and grouped moment resisting connectors and the study of the wood properties under embedment. The proposal of this paper is to approach these aspects, and to quantitatively study the influence of the moment resistant connection in wooden framed structures. Comparisons between rigid and semi-rigid connections and between linear and nonlinear analysis lead to quantitative results.

• Journal of Forest and Environmental Science
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• 제22권1호
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• pp.41-49
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• 2006

일본에서 2004년도에 발행된 산림토목 목제구조물 시공 매뉴얼에 실려 있는 산림토목 목제구조물 설계지침은 총설, 목재의 이용과 특성, 조사, 계획 및 설계 등으로 구성되어 있으며, 이 논문에서는 총설, 목재의 이용과 특성, 조사 및 계획에 대하여 분석하였다. 분석 결과, 목재의 특성은 목재의 물리 화학적 특성, 환경에의 영향, 심리 생리적인 효과 및 목재의 부후성에 대해 정리되어 있으며, 조사항목은 유수에 의한 영향의 정도, 일사의 정도, 흰개미의 생식 유무, 지표수 및 지하수의 유하 상황, 계류 등에 서식하는 동식물의 상황, 물이용 상황 등이 제시되었다. 또한 계획에서는 목제구조물의 구조와 설치장소, 취급방법, 해당 지역의 목재 간벌재의 이용, 방부처리 등에 대하여 설명되어 있다.

• Journal of the Korean Wood Science and Technology
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• 제20권4호
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• pp.21-30
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• 1992

An activation energy equation for moisture diffusion in wood was developed with an assumption that activation energy is directly proportional to wood specific gravity. Theoretical activation energies obtained from the activation energy equation were revealed to be always lower than actual activation energies, which implies that activation energy isn't affected only by wood specific gravity. The other affecting factors are possibly anatomical structures of wood which determine a ratio of vapor diffusion to bound water diffusion in wood. For the convenience of estimating actual activation energy by using the activation energy equation, thirteen kinds of species were categorized into three groups according to their anatomical structures.

• Wind and Structures
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• 제19권6호
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• pp.603-621
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• 2014

Past high speed wind events have exposed the vulnerability of the roof systems of existing light-framed wood structures to uplift loading, contributing greatly to economic and human loss. This paper further investigates the behaviour of light-framed wood structures under the uplift loading of a realistic pressure distribution. A three-dimensional finite-element model is first developed to capture the behaviour of a recently completed full-scale experiment. After describing the components used to develop the numerical model, a comparison between the numerical prediction and experimental results in terms of the deflected shape at the roof-to-wall connections is presented to gain confidence in the numerical model. The model is then used to analyze the behaviour of the truss system under realistic and equivalent uniform pressure distributions and to perform an assessment of the use of the tributary area method to calculate the withdrawal force acting on the roof-to-wall connections.

• Journal of the Korean Wood Science and Technology
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• 제22권3호
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• pp.26-31
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• 1994

To provide further information for reutilization of the waste wood obtained after cultivating oak mushroom in Kangwon-do, the crystal structures of the waste wood were investigated and compared to those of normal woods by a series of x-ray diffraction analysis. The results obtained are as follows: 1. An x-ray diffraction diagram of cultivated wood for 5 years was same as that of typical cellulose with some orientation of cellulose crystallites, but that of cultivated wood for 8 years a random. 2. Crystallinity indices in normal and cultivated woods for 5 years ranged from 57% to 60%. In the cultivated wood for 8 years, however, the value showed about 40%. 3. Crystallite widths of cultivated woods for 5 years and for 8 years were 3 nm and 2.5 nm, respectively. 4. Intensity ratios of equatorial and meridional layers did not show any significant differences. From the above results, it is clear that the waste wood obtained after cultivating oak mush room for 5 years showed basically same crystal structures with normal wood. Therefore, we think that the waste wood may be used available for cellulosic material instead of normal wood.

• 국제초고층학회논문집
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• 제9권1호
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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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• 제34권5호
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• pp.19-28
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• 2006

There has been considerable research in recent times in light-timber med structures in fires. These structures have included horizontal (floor-like) panels in bending and walls under eccentric and approximately concentric vertical loading. It has been shown that compression properties are the most dominant mechanical properties in affecting structural response of these structures in fire. Compression properties have been obtained by various means as functions of one variable only, temperature. It has always been expected that compression properties would be significantly affected by moisture and stress, as well. However, these variables have been largely ignored to simplify the complex problem of predicting the response of light-timber framed structures in fire. Full-scale experiments on both the panels and walls have demonstrated the high level of significance of moisture and stress for a limited range of conditions. Described in this paper is an overview of these conditions and experiments undertaken to obtain compression properties as a functions of moisture, stress and temperature. The experiments limited temperatures to $20{\sim}100^{\circ}C$. At higher temperatures moisture vaporizes and moisture and stress are less significant. Described also is a creep model for wood at high temperatures.

• Journal of the Korean Wood Science and Technology
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• 제45권5호
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• pp.483-494
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• 2017

본 총설에서는 목재의 기상열화 특성(색상, 목재표면의 미세구조 및 화학적 변화)과 국제적으로 다양하게 이용되는 내후성시험방법에 관한 국제적 연구동향에 대하여 보고한다.