• 대한기계학회논문집A
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• 제30권10호
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• pp.1269-1275
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• 2006

The purpose of this study is to investigate the effect of bend angle on the collapse behavior of locally wall thinned pipe bends. For this purpose, the present study performed three-dimensional finite element analysis on the 30-, 60-, and 90-degree pipe bends with local wall thinning at the center of intrados, extrados, and crown, and evaluated the collapse moment for different thinning dimensions under closing- and opening-mode bending with a constant internal pressure. The results showed that, for intrados and extrados wall thinning, the reduction in the collapse moment due to local wall thinning became significant with decreasing bend angle of pipe bends. This effect of bend angle was enhanced with increasing thinning dimensions, and it was clearer fur opening-mode bending than for closing-mode bending. For crown wall thinning, however, the effect of bend angle was unclear and was less sensitive to the change of wall thinning shapes.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.153-156
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• 2008

Comparative analysis of forest fire danger rating on the forest characteristics of thinning area and non-thinning area on forest fire burnt area was studied in this work. To investigate the effect of thinning slash in forest fire, Gangneung-si Wangsan-myeon, Ulgin-gun Wonnam-Myeon, Samchok-si Gagok-Myeon, in which forest fire broke out, were selected. As a result that investigated forest fire danger ratio between thinning slash and non-thinning slash, leeward scorching ratio(36%), crown damage ratio(29%), mortality of branch at the former are higher than those at the latter, leeward scorching ratio of tree, where thinning slash is around, is 10%-20% higher than that of independent tree. So I estimate that thinning slash has a some effect on the intensity of forest fire. And the result to investigate damage of forest fire according to tree species shows that leeward scorching ratio of conifer is 5% higher than that of non-conifer, and mortality of branch of the former is 19% higher than that of the latter. It is considered that forest fire may affect directly to a tree trunk if it diffuse to piled thinning tree because there was no space between thinning trees and trees. Furthermore, it was found that re-ignition had a chance to occur due to lots of piled thinning trees.

• Journal of Forest and Environmental Science
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• 제33권1호
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• pp.74-77
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• 2017

The purpose of this study is to analyze the effect of thinning intensity on the growth of large diameter trees in Korean white pine (Pinus koraiensis S. et Z.) plantation. Eight thinning plots were analyzed by categorizing into heavy thinning, light thinning, no thinning (control) according to thinning intensity. As a result, average DBH increased more in heavy thinning plots than in light thinning or unthinned plots. The number of large trees (DBH>25 cm) were obviously shown the most in heavy thinning plots. It is considered that heavy thinning is needed for the production of the large diameter trees.

• 대한기계학회논문집A
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• 제28권4호
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• pp.402-409
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• 2004

The purpose of this study is to investigate the effect of local wall thinning on the collapse of elbow subjected to internal pressure and bending moment. Thus, the nonlinear three-dimensional finite element analyses were performed to obtain the collapse moment of elbow containing various wall thinning defects located at intrados and extrados under two loading modes (closing and opening modes) with internal pressure. From the results of analysis, the effect of wall thinning defect on the global moment-rotation behavior of elbow was discussed, and the dependence of collapse moment of elbow on wall thinning depth, length, and circumferential angle was investigated under different loading mode and defect location.

• 대한기계학회논문집A
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• 제31권5호
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• pp.586-593
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• 2007

This paper proposes closed-form plastic limit load solutions for elbow with local wall thinning at extrados under internal pressure. This work was performed using 3-dimensional, small strain FE analyses based on elastic-perfectly plastic materials. The wide range of elbow and local wall thinning geometries are considered. For systematic analyses for effect of axial thinning extent on limit loads, two limiting cases are considered; a sufficiently long thinning, and the circumferential part-through surface crack. Then, the closed-form plastic limit load solutions for intermediate thinning are obtained by using result of two limiting cases. The effect of axial thinning extent for elbow on plastic limit load is highlighted by comparing with that for straight pipes. Although the proposed limit load solutions are developed for the case when local wall thinning exist in the center of elbow, it is also shown that they can be applied to the case when local wall thinning exists anywhere within elbow.

• 대한기계학회논문집A
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• 제31권4호
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• pp.496-505
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• 2007

This paper proposes closed-form plastic limit load solutions for elbows under in-plane bending, via three-dimensional (3-D), small strain FE limit analyses using elastic-perfectly plastic materials. A wide range of elbow and thinning geometries are considered. For systematic analyses of the effect of the axial thinning length on limit loads, two limiting cases are considered; a sufficiently long wall thinning, and the circumferential part-through surface crack. Closed-form plastic limit load solutions for wall thinning with intermediate longitudinal extents are then obtained from these two limiting cases. The effect of the axial extent of wall thinning on plastic limit loads for elbows is highlighted by comparing that for straight pipes. Although the proposed solutions are developed for the case when wall thinning exists in the center of elbows, it is also shown that they can be applied to the case when wall thinning exists anywhere within the elbow.

• 한국안전학회지
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• 제20권1호
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• pp.55-61
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• 2005

The purpose of this study is to investigate the effect of circumferential location of local wall thinning defect on the collapse behavior of an elbow. Thus, the present study conducts three-dimensional finite element analysis on the 90-degree elbow containing a local wall thinning at intrados, crown and extrados of bend region and evaluates the collapse moment of wall thinned elbow under various thinning shapes and loading conditions. Combined internal pressure and bending moment are considered as an applied load. The internal pressure of $0\~20MPa$ and both closing and opening mode bending are employed. The results of analysis show that the reduction in collapse moment of the elbow by local wall thinning is more significant for a defect locating at crown than for a defect locating at intrados or at extrados. Also, the effect of internal pressure on the collapse moment of wall thinned elbow depends on the circumferential location of thinning defect and applied bending mode.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.622-628
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• 2003

The purpose of this study is to evaluate the effect of local wall thinning on the collapse of elbow subjected to internal pressure and bending moment. Thus, the nonlinear 3D finite element analyses were performed to obtained collapse moment of elbow containing various wall thinning defects under two loading; modes (closing and opening modes) and defect locations (intrados and extrados). From the results of analyses, the influence of wall thinning defect on the global moment-rotation behavior of elbow was discussed, and the dependance of collapse moment of elbow on wall thinning depth, length, and circumferential angle was investigated under different loading mode and defect location.

• 한국산림과학회지
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• 제104권4호
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• pp.527-535
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• 2015

본 연구는 간벌에 따른 국내 산림의 직경 생장량과 탄소 저장량(임목, 고사목, 낙엽층, 토양) 변화를 파악하기 위하여 관련 결과들을 메타 분석한 것이다. 메타 분석 결과 간벌에 의하여 직경 생장량과 토양 탄소 저장량은 각각 39.2% 및 12.8% 증가하였고 임목 탄소 저장량은 30.9% 감소하는 것으로 나타났다. 그러나 고사목과 낙엽층 탄소 저장량은 간벌에 따른 변화를 보이지 않았다. 한편 직경 생장량과 임목 탄소 저장량은 간벌 강도 및 회복 시간(간벌 후 시간의 경과)과 상관 관계를 보였다. 그리고 낙엽층 탄소 저장량은 회복 시간과 상관 관계를 보였으나, 고사목과 토양 탄소 저장량은 간벌 강도 및 회복 시간과 상관 관계를 보이지 않았다. 또한 간벌 강도와 회복 시간에 따른 직경 생장량과 임목 탄소 저장량의 회귀식을 개발하였다. 고사목, 낙엽층 그리고 토양 탄소 저장량은 간벌 강도와 회복 시간과의 상관 관계가 거의 나타나지 않았으므로, 이들의 변화를 정량화하기 위해서는 본 연구에서 개발한 임목 탄소 저장량 회귀식과 산림 탄소 모델의 연계가 필요할 것으로 판단된다. 간벌에 의한 산림의 변화를 보다 정확하게 파악하기 위하여 연구 대상 수종 확대, 장기 모니터링 및 측정 주기 단축, 그리고 하층 식생 조사 등을 제언하였다.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.719-722
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• 2008

Forest management is done to keep ecological health of forest and to enhancement of its function. Nowadays, the abnormal climate and heavy rain happen frequently. Therefore, there are opinions that the thinning slash allowed in the mountain is flowed in rivers, which can influence in flood damage. This study, we grasp moving characteristics of thinning slash through field survey and achieved basic study about the effect of thinning slash on the discharge capacity of rivers and stream structure.