Journal of the Korean Wood Science and Technology

The Korean Society of Wood Science & Technology (한국목재공학회)
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Determination of Grades and Design Strengths of Machine Graded Lumber in Korea

국내 기계등급구조재의 등급구분체계 및 기준설계값 결정방법 연구

  • Hong, Jung-Pyo (Research Institute for Agriculture and Life Sciences, Seoul National University) ;
  • Lee, Jun-Jae (Department of Forest Sciences, College of Agriculture and Life Sciences, Seoul National University) ;
  • Park, Moon-Jae (Department of Forest Products, Korea Forest Research Institute) ;
  • Yeo, Hwanmyeong (Department of Forest Sciences, College of Agriculture and Life Sciences, Seoul National University) ;
  • Pang, Sung-Jun (Department of Forest Sciences, College of Agriculture and Life Sciences, Seoul National University) ;
  • Kim, Chul-Ki (Department of Forest Sciences, College of Agriculture and Life Sciences, Seoul National University) ;
  • Oh, Jung-Kwon (Research Institute for Agriculture and Life Sciences, Seoul National University)
  • 홍정표 (서울대학교 농업생명과학연구원) ;
  • 이전제 (서울대학교 산림과학부) ;
  • 박문재 (국립산림과학원 임산공학부) ;
  • 여환명 (서울대학교 산림과학부) ;
  • 방성준 (서울대학교 산림과학부) ;
  • 김철기 (서울대학교 산림과학부) ;
  • 오정권 (서울대학교 농업생명과학연구원)
  • Received : 2015.03.25
  • Accepted : 2015.05.13
  • Published : 2015.07.25
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Abstract

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.

국내외 기계등급제재목(구조재 및 층재)의 등급기준 및 설계강도 산출방법을 비교 분석하고 국내 제재산업 실정을 고려한 평균 탄성계수(modulus of elasticity, 이하 MOE) 기준방법 적용을 제안하였다. 먼저 올바른 기계등급제재목 기준 정착을 위해 기계등급구조재와 기계등급층재의 공통점과 차이점을 설명하였다. 최소 고정 MOE 기준 등급을 사용하는 국내 기준은 등급구분에는 편리하나 휨강도(modulus of rupture, 이하 MOR) 예측과 자원이용도 측면에서는 효율성이 낮은 것으로 파악되었다. 해외에서 사용되는 평균 MOE 기준 방법은 초기 컴퓨터 기반 작동을 요구하나 MOR-MOE 직선회귀에 근거한 합리적인 MOR 예측과 품질관리 측면에서 효율성이 높은 것으로 분석되었다. 무엇보다도 현 국내 기계등급구조재 등급체계는 수종별 강도 특성을 반영하지 못하고 있다는 것이 가장 큰 문제점으로 분석되었으며 이러한 결과를 기반으로 MOR-MOE 직선회귀분석에 근거한 기계등급제재목 등급기준 및 기준설계값 산출방법 적용을 제안하였다. 이를 통하여 궁극적으로 부가가치가 높은 국산 기계등급구조재 생산 활성화를 이루고, 기계 등급구조재의 층재 전용 가능에 따른 구조용 집성재 가격경쟁력 제고 효과를 얻을 수 있다고 사료되었다.

Keywords

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