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白点基 부산대학교 공과대학 1990 硏究報告 Vol.40 No.-
In order to carry out a reliable design and safety assessment of structures, reliability-based design technique which takes the statistical uncertainty of random variable into account becomes to be of great interest. For ship structures, in particular, an attempt for the standardization of the safety index(level 2) has been performed for the existing ships which are considered to have sufficient structural safety. In this study, a practical approach using MVFOSM method for the ultimate strength-based reliability assessment is formulated for the upper deck structures subjected to uniaxial compression which is induced by the action of sagging moment. Then safety indices for the actual ship structures are evaluated and also the influence of the initial imperfection and material property of the structure on the safety index is investigated.
2축 방향 압축력을 받는 판요소의 좌굴 및 좌굴후 거동에 미치는 용접잔류응력의 영향
백점기,정윤식,엄동석 釜山大學校 生産技術硏究所 1994 生産技術硏究所論文集 Vol.47 No.
Effects of welding residual stress on buckling and post-puckling behavior of simply supported rectangular plates under biaxial compression are investigated, and accuracy and applicability of the plate buckling design formula proposed by the authors are checked. It is concluded that the plate buckling strength is seriously affected by the welding residual stress distributed in transverse as well as longitudinal direction. Also as the compressive residual stress increases the buckling strength decreases when the compressive residual stress block is distributed in the middle, whileas it increases when the tensile residual stress block is distributed in the middle. 본 논문에서는 주변단순지지된 선체판요소가 2축방향 압축력을 받는 경우의 좌굴 및 좌굴후 거동에 미치는 용접잔류응력의 영향을 고찰하고, 용접잔류응력항을 고려하여 저자들이 제안한 바 있는 간이좌굴설계공식의 정도와 적용성을 검토하였다. 연구결과, 좌굴강도는 종방향뿐만 아니라 횡방향의 잔류응력에도 영향을 받으며, 판의 중앙부에 압축잔류응력이 분포하는 경우에는 좌굴강도가 저하하지만, 판의 중앙부에 인장잔류응력이 분포하는 경우에는 오히려 좌굴강도가 증가함을 알았다. 또한, 기 제안한 바 있는 좌굴설계공식은 판의 중앙부에 압축잔류응력이 분포하는 경우, 이론해석 결과와 잘 일치하고 있다는 것을 확인하였다.
白点基,柳廷錫,李晩承 부산대학교 공과대학 1990 硏究報告 Vol.40 No.-
In ship structure, the corner of the hatch opening on the main deck is one of the hot spot in the sense that stress concentration resulting in initiation of the fatigue crack damage is occured under the action of the repeated loading. In order to perform a more reliable design of ship structure, it is very important to carry out safety assessment on the basis of fatigue strength as well as bucking or ultimate strength. In this study, stress analysis of the corner of the main deck hatch opening for 30 actual ships in conducted by using FEM. Based on these results, stress concentration factor and fatigue life are predicted. It is observed from the result of this study that the stress concentration factor of the objective ships are ranged from 2.1 to 8.2 and fatigue life from 2 to 4 years in general.