• 대한조선학회논문집
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• 제52권2호
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• pp.161-169
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• 2015

According to SOLAS Regulation XII/6.5.3 and IMO GBS functional requirement(IMO, 2010), the structural redundancy of multi-bay stiffened panel in cargo area of bulk carrier should be provided enough in order to endure the initial design load though one bay of the stiffened panel is damaged due to plastic deformation or fatigue crack. To satisfy structural redundancy, Harmonized Common Structural Rules (hereinafter CSR-H, IACS, 2014) proposed to use 1.15 instead of 1.0 for buckling usage factor of stiffened panel in cargo area. This paper shows that buckling usage factor in CSR-H for structural redundancy is somewhat conservative considering the ultimate strength calculated by using nonlinear FEA for the damaged condition which is only one bay's plastic deformation due to colliding by weigh object like a bucket. Also, this paper presents that increasing of plate thickness only is more effective to get enough structural redundancy.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.699-710
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• 2020

Pitting corrosion commonly shaped in hull structure due to marine corrosive environment seriously causes the deterioration of structural performance. This paper deals with the ultimate strength behaviors of stiffened ship panels damaged by the pits subjected to uniaxial compression. A series of no-linear finite element analyses are carried out for three stiffened panels using ABAQUS software. Influences of the investigated typical parameters of pit degree (DOP), depth, location and distribution on the ultimate strength strength are discussed in detail. It is found that the ultimate strength is significantly reduced with increasing the DOP and pit depth and severely affected by the distribution. In addition, the pits including their distributions on the web have a slight effect on the ultimate strength. Compared with regular distribution, random one on the panel result in a change of collapse mode. Finally, an empirical formula as a function of corrosion volume loss is proposed for predicting the ultimate strength of stiffened panel.

• Smart Structures and Systems
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• 제14권4호
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• pp.569-594
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• 2014

Damage detection methods based on modal analysis have been widely studied in recent years. However the calculation of mode shapes in real structures can be time consuming and often requires dedicated software programmes. In the present paper the combined application of proper orthogonal decomposition and gapped smoothing method to structural damage detection is presented. The first is used to calculate the dynamic shapes of a damaged structural element using only the time response of the system while the second is used to derive a reference baseline to which compare the data coming from the damaged structure. Experimental verification is provided for a beam case while numerical analyses are conducted on plates. The introduction of a stiffener on a plate is investigated and a method to distinguish its influence from that of a defect is presented. Results highlight that the derivatives of the proper orthogonal modes are more effective damage indices than the modes themselves and that they can be used in damage detection when only data from the damaged structure are available. Furthermore the stiffened plate case shows how the simple use of the curvature is not sufficient when analysing complex components. The combined application of the two techniques provides a possible improvement in damage detection of typical aeronautical structures.

• Composites Research
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• 제12권6호
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• pp.74-82
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• 1999

폴리 우레탄 폼 코아 샌드위치 복합재료의 정적 및 피로 특성에 대하여 연구하였다. 유리 섬유강화 스킨과 중합의 폼 코아를 갖는 비스티칭, 스티칭, 스티프너의 세 종류 시편이 사용되었다. 특히 스티칭 샌드위치 구조는 두께 방향에 대하여 폴리에스터와 유리섬유를 꼬아서 부가적인 구조 보강이 코아의 상하 표면을 통하여 꿰멘 구조로 층간분리를 최소화하기 위해 샌드위치 구조 패널을 스티칭하여 만들고 수지는 수지의 유동 온도에서 수지의 낮은 점도 특성을 이용하여 스티칭 섬유에 침투시켜 함께 경화하였다. 스티칭 섬유가 $50{\times}50{\;}mm$의 간격으로 스티칭된 시편 및 스티프너 시편의 굽힘강도는 비스티칭 시편과 비교하여 각각 50%및 10배 이상으로 향상되었다. 최대 하중의 20%크기로 $10^6$ 피로 사이클을 받은 후, 비스티칭 시편의 굽힘 피로강도는 정적 굽힘강도와 비교하여 27%까지 감소되었고, 스티칭된 시편은 39%,그리고 스티프너에 의하여 보강된 시편은 20%정도 감소되었다. 폴리우레탄 폼 코아의 에이징 효과를 입증하기 위해, 피로 시험 후 샌드위치 시편의 표면 적층의 손상은 초음파 C-scan장비를 사용하여 검출하였다. 초음파 C-scan결과로부터 피로 시험동안 손상 받은 어떤 결함도 없었다 이는 피로 사이클동안 폼 코아 샌드위치 구조에 대한 굽힘강도의 감소는 폴리우레탄 폼이 에이징되어 발생하는 것을 의미한다.