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Advanced Idealized Structural Units Considering the Excessive Tension-Deformation Effects
백점기,Jeom-K. Paik The Society of Naval Architects of Korea 1993 大韓造船學會 論文集 Vol.30 No.3
In this paper, the extent of use of three kinds of the existing idealized structural units, namely the idealized beam-column unit, the idealized unstiffened plate unit and the idealized stiffened plate unit, is expanded to deal with the excessive tension-deformation effects, in which a simplified mechanical model for the stress-strain relation of steel members under tensile load is suggested. The 1/3-scale hull model for a leander class frigate under sagging moment tested by Dow is analyzed, and it is shown that the excessive tension-de-formation is a significant factor affecting the progressive collapse behavior, particularly in the post-collapse range. 본 논문에서는 구조전체의 최종붕괴강도에 대한 국부 구성부재의 과도인장변형효과를 고려하기 위하여 기존의 이상화구조요소들, 즉 이상화 보-기동요소, 이상화 판요소 및 이상화 보강판요소의 적용범위를 확장하며, 이를 위해 간이 역학적모델을 제시한다. Leander급 Frigate함의 1/3 축척 선각구조모형에 대해 Dow가 수행한 최종 종강도실험결과와 본 해석결과를 비교한 결과, 압축에 의한 구조부재의 파손 뿐만아니라 과도인장변형에 의한 파손도 구조전체적인 붕괴거동, 특히 붕괴후 거동에 크게 영향을 미침을 알 수 있었다.
백점기,Jeom-K. Paik The Society of Naval Architects of Korea 1991 大韓造船學會 論文集 Vol.28 No.1
본 연구에서는 압축최종강도(壓縮最終强度)를 기준으로 한 이중갑판구조(二重甲板構造)의 실용적인 안전성(安全性) 및 신뢰성(信賴性) 평가법을 제안한다. 이를 위하여 선체상갑판(船體上甲板)에 작용하는 압축응력(壓縮應力)을 기존의 선급규정에 의해 근사적으로 추정하며, 압축최종강도(壓縮最終强度)는 이상화구조요소법(理想化構造要素法)을 적용하여 해석한다. 초기(初期)처짐 및 잔류응력(殘留應力)의 영향과 국부좌굴(局部挫屈) 및 전체좌굴(全體挫屈)의 상관효과(相關效果)를 고려한 이상화판요소(理想化板要素)를 정식화한다. 이상화판요소(理想化板要素)의 정도(精度)와 유용성(有用性)은 단위(單位) 판부재(板部材) 및 상자형 용접구조물(熔接構造物)에 대한 기존의 실험결과(實驗結果) 또는 유한요소해석결과(有限要素解析結果)와 비교하여 확인한다. 본 제안법을 이중선각구조설계(二重船殼構造設計)개념하에서 설계된 정유운반선(精油運搬船)의 갑판구조(甲板構造)의 안전성(安全性) 및 신뢰성평가(信賴性評價)에 적용하고, 초기처짐, 잔류응력(殘留應力)등의 영향과 고장력강(高張力鋼)을 사용한 경우의 효과등에 대해 고찰한다. A practical procedure for the ultimate compressive strength-based safety and reliability assessment of the double skin upper deck structure is described. The external compressive stress acting on the upper deck structure which is due to the still water and wave-induced sagging moment is approximately estimated by using the existing rule of classification society. The ultimate compressive stress of double skin structure under the action of sagging moment is analyzed by using idealized structural unit method. Here an idealized plate element subjected to uniaxial load is formulated by idealizing the nonlinear behaviour of the actual element taking account of the initial imperfections in the form of initial deflection and welding residual stress. The interaction effect between the local and global failure in the structure is also taken into consideration. The accuracy of the present method is verified comparing with the present solution and the existing numerical and experimental results for unit member and welded box columns. The safety of the structure is evaluated using the concept of conventional central safety factor and the reliability assessment is made by using Cornel's MVFOSM method. The present procedure is then applied to upper deck structure of double skin product oil carrier. The influence of the initial imperfections and the yield stress of the material on the safety and reliability of the structure is investigated.
Considerations of the Initial Crack Damage Effect on the Advanced Idealized Plate Unit
백점기,서흥원,Paik, Jeom-K.,Suh, Heung-W. The Society of Naval Architects of Korea 1994 大韓造船學會 論文集 Vol.31 No.2
This paper attempts to incorporate the initial crack damage effect into the existing idealized plate unit. For this purpose, a new concept which indicates the equivalent, reduced material properties due to initial cracks at the structural unit level, not at he microscopic aspect, is suggested, and a simplified mechanical plate model for the initially cracked plate in axial tension is formulated as a function of initial crack length, based on the finite-element solutions obtained by crack propagation analysis.