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탄소성이방성 솔리드 유한요소법 활용을 위한 목재 재료 모델 생성 연구
홍정표 ( Jung Pyo Hong ),김철기 ( Chul Ki Kim ),이전제 ( Jun Jae Lee ),오정권 ( Jung Kwon Oh ) 한국목재공학회 2014 목재공학 Vol.42 No.4
A simplified material model, which was efficiently implemented in a three-dimensional finite solid element (3D FE) analysis for wood was developed. The bi-linear elasto-plastic anisotropic material theory was adopted to describe constitutive relations of wood in three major directions including longitudinal, radial and tangential direction. The assumption of transverse isotropy was made to reduce the requisite 27 material constants to 6 independent constants including elastic moduli, yield stresses and Poisson`s ratios in the parallel, and perpendicular to grain directions. The results of Douglas fir compression tests in the three directions were compared to the 3D FE simulation incorporated with the wood material model developed in this study. Successful agreements of the results were found in the load deformation curves and the permanent deformations. Future works and difficulties expected in the advanced application of the model were discussed.
국내 기계등급구조재의 등급구분체계 및 기준설계값 결정방법 연구
홍정표 ( Jung Pyo Hong ),이전제 ( Jun Jae Lee ),박문재 ( Moon Jae Park ),여환명 ( Hwan Myeong Yeo ),방성준 ( Sung Jun Pang ),김철기 ( Chul Ki Kim ),오정권 ( Jung Kwon Oh ) 한국목재공학회 2015 목재공학 Vol.43 No.4
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.
홍정표 ( Jung Pyo Hong ),오정권 ( Jung Kwon Oh ),박주생 ( Joo Saeng Park ),한연중 ( Yeon Jung Han ),방성준 ( Sung Jun Pang ),김철기 ( Chul Ki Kim ),이전제 ( Jun Jae Lee ) 한국목재공학회 2015 목재공학 Vol.43 No.4
365 pieces of domestic 38 × 140 × 3600 mm Red pine structural lumber were machine graded conforming to a softwood structural lumber standard (KS F 3020). The allowable bending stresses calculated for each grade were compared with the values currently tabulated in the standard. Four calculation methods for lower 5th percentile bending stress were non-parametric estimation with 75% confidence level, 2-parameter and 3-parameter Weibull distribution fit, and bending modulus of rupture (MOR)-modulus of elasticity (MOE) regression based method. Only the data set of Grades E8, E9, and E10 were statistically eligible for the 5th percentile calculation. The MOR-MOE regression based method only was able to estimate the lower 5th percentile values theoretically for the full range of grades. The results showed that all allowable bending stresses calculated were lower than the design values tabulated in the standard. This implies that the current machine grading system has the pitfall of structural safety. Improvement in current machine grading system could be achieved by introducing the bending strength and stiffness combination grade system.
임진아 ( Jin A Lim ),오정권 ( Jung Kwon Oh ),여환명 ( Hwan Myeong Yeo ),이전제 ( Jun Jae Lee ) 한국목재공학회 2010 목재공학 Vol.38 No.6
In this study, the visual grading based on the visual characteristics and structural timber bending test were conducted for domestic yellow poplar dimension lumber. Structural performance of domestic yellow poplar dimension lumber was conducted through the evaluation of strength and stiffness. Visual grading rule of yellow poplar dimension lumber did not exist in Korea. Visual grading of yellow poplar dimension lumber was performed according to the NSLB (Northern Softwood Lumber Bureau) standard grading rules including several hardwood dimension lumber. The allowable bending stress was calculated from the results of a visual grading. Compared with DS (National Design Specification), the yellow poplar dimension lumber showed enough strength for structural uses. In addition, the visual grading was performed according to the KFRI (Korea Forest Research Institute) grading rule to calculated allowable bending stress and to evaluated the feasibility. The yellow poplar was classified into the pine groups by the KFRJ criteria regulated by specific gravity. Allowable bending stress based on weibull distribution had became highly than KFRI criteria, as No. 1 (10.0 MPa), No.2 (7.4 MPa) and No.3 (4.1 MPa). And the availability of yellow poplar dimension lumber for structural uses had been confirmed. The Modulus of Elasticity (MOE) of domestic yellow poplar dimension lumber had not met the NDS and KFRI criteria. However, for the use of domestic yellow poplar, average values of MOE which obtained through this test were suggested as design value for domestic yellow poplar. Design values were supposed o. 1, 2 (9,000 MPa and No.3 (8,000 MPa).
< 구두-A-09 > 목재-콘크리트 복합 바닥 시스템의 Screw 전단 접합부 평가
이현정 ( Hyeon-jeong Lee ),오정권 ( Jung-kwon Oh ) 한국목재공학회 2019 한국목재공학회 학술발표논문집 Vol.2019 No.1
Timber-Concrete Composite(TCC) can provide higher stiffness as floor system. TCC is a type in which timber resistant to the tensile force and concrete resistant to the compressive force are connected by shear connectors, so the performance of the shear joint can be dominated to determine the performance of TCC. As a preliminary experiment to determine the performance of the shear connection of TCC, a slip test was carried out. Self-tapping screw (STS) was used for TCC shear connectors in consideration of the convenience of installation and existing researches. The prefabricated method was used in which STS was installed at regular intervals on larch glulam and concrete was poured thereon for curing. As a result of the experiment, slip modulus of TCC was changed according to the installation direction of STS. Withdrawal capacity was a decisive effect on the performance of shear connectors in TCC, and bent motion didn’t affect or reduced the performance of shear connectors in TCC.
동등성능 철근콘크리트, 강재, 목재 보의 온실가스 배출량 및 내재 에너지 분석
오재원 ( Jae-won Oh ),방성준 ( Sung-jun Pang ),안경선 ( Kyung-sun Ahn ),김지용 ( Ji-yong Kim ),김민정 ( Min-jeong Kim ),장윤성 ( Yoon-seong Chang ),오정권 ( Jung-kwon Oh ) 한국목재공학회 2022 한국목재공학회 학술발표논문집 Vol.2022 No.1
최근 지속 가능한 발전에 관한 관심이 커지며, 전과정평가를 통한 환경 영향 평가가 활발하게 이루어지고 있다. 건축 부문에서도 하나의 건물을 대상으로 자재 생산부터 시공, 운영, 철거까지 전과정의 환경 영향 평가가 수행되고 있다. 그러나, 개별 평가 결과는 대상 건물의 설계조건이 상이하여 건축 재료에 따른 환경 영향을 비교하기에 어려움이 있다. 본 연구에서는 동등한 구조 성능을 가진 철근콘크리트, 강재, 목재 보의 온실가스 배출량과 내재 에너지를 비교 분석하였다. 동등한 성능으로 설계하기 위해 사용 재료와 단면 형상을 제외한 모든 조건을 동일하게 가정하여 설계하였고, 기능 단위는 보의 1m로 시스템 경계는 원자재 채취, 수송 및 제품 생산까지의 과정으로 정의하여 평가를 진행했다. 온실가스 배출량은 철근콘크리트, 강재, 목재의 비가 약 1.0, 1.8, 0.7로 나타났고, 내재 에너지도 이와 유사한 경향으로 나타났다. 단위 부피 생산 과정의 온실가스 배출량과 내재 에너지는 철근콘크리트, 강재, 목재의 비가 약 26, 1.0, 0.5 수준으로 본 연구의 결과와 큰 차이가 있음을 확인했다. 추후 연구에서는 동등한 성능을 가진 전체 구조체를 대상으로 전과정평가를 수행하여 연구 내용을 보완할 예정이다.
구조적 관점에서의 콘크리트, 목재 슬래브의 환경 영향 비교
오재원 ( Jae-won Oh ),박금성 ( Keum-sung Park ),김익 ( Ik Kim ),오정권 ( Jung-kwon Oh ) 한국목재공학회 2022 한국목재공학회 학술발표논문집 Vol.2022 No.2
목재는 친환경 건축 재료로 주목을 받고 있지만, 기존의 건물을 목재로 대체하여 얻는 환경적인 이득에 대한 연구는 미비한 실정이다. 목조 건물은 표본이 부족하여 통계적 분석이 어렵고, 기능적으로 동등한 건물을 설계하여 환경 영향을 비교하는 것은 구조적 효율성이 동등하지 않아 결과가 편향될 수 있기 때문이다. 본 연구에서는 목재의 환경적인 이득을 객관적으로 평가하기 위해 구조적 성능이 동등한 RC(Reinforced Concrete), CLT(Cross-Laminated Timber), TCC(Timber-Concrete Composite) 슬래브의 환경 영향을 비교하였다. 슬래브의 구조 성능은 단일 지표로 표현될 수 없기에 경간과 활하중이 같으면 구조 성능이 동등하다고 보았다. 슬래브를 다양한 경간과 활하중 조건에서 설계하고, 전과정평가 방법론을 활용하여 환경 영향을 평가했다. 환경 영향의 지표로 사용된 온실가스 배출량은 환경성능 인증제품의 데이터를 활용하였다. 분석 결과, 슬래브의 온실가스 배출량은 RC, TCC, CLT 순으로 높게 나타났다. 유일하게 TCC는 경간이 길어질수록 상대적인 환경 영향이 감소하는 경향을 보였다. 슬래브의 두께 또한 CLT, TCC의 두께가 RC보다 얇게 설계되어도 동등한 구조 성능을 낼 수 있음을 확인하였다. 이와 같은 결과를 미뤄보아 목조 구조가 환경적으로 우수하며 구조적으로도 합리적인 대안을 제시할 수 있음을 확인할 수 있었다.