• 한국농공학회지
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• 제43권1호
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• pp.122-128
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• 2001

The theory of non-prismatic folded plate structures was reported by D.H. Kim in 1965 and 1966. Fiber reinforced composite materials are strong in tension. The structural element for such tension force is very thin and weak against bending because of small bending stiffnesses. Naturally, the box type section is considered as the optimum structural configuration because of its high bending stiffnesses. Such structures can be effectively analyzed by the folded plate theory with relative ease. The “hollow” bending membr with uniform cross-section can be treated as prismatic folded plates which is a special case of the non-prismatic folded plates. In this paper, the result of analysis of a folded plates with one box type uniform cross-section is presented. Each plate is made of composite laminates with fiber orientation of [ABBCAAB]r, with A=-B=45${\circ}C$, and C=90${\circ}$. The influence of the span to depth ratio is also studied. When this ratio is 5, the difference between the results of folded plate theory and beam theory is 1.66%.

• Structural Engineering and Mechanics
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• 제13권2호
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• pp.155-170
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• 2002

In this study, a new functional is obtained for folded plates with geometric (kinematic) and dynamic (natural) boundary conditions. This functional is the combination of two different functionals. Both functionals are obtained for thick plates which carry in-plane and lateral forces. A new mixed finite element is developed with $4{\times}13$ nodal parameters for folded plates (REC52). Forces and moments which are the necessary unknowns in engineering problems are obtained directly using the technique suggested here. The use of the global co-ordinate system causes time consuming operations and therefore the Lagrange multiplier method is used to relate the components of the parameters on the fold line. Numerical results are presented for folded plates and compared with experimental results.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
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• pp.93-96
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• 2000

The theory of non-prismatic folded plate structures was reported by the senior author in 1965 and 1966. Fiber reinforced composite materials are strong in tension. The structural element for such tension force is very thin and weak against bending because of small bending stiffnesses. Naturally, the box type section is considered as the optimum structural configuration because of its high bending stiffnesses. Such structures can be effectively analyzed by the folded plate theory with relative ease. The "hollow" bending member with uniform cross-section can be treated as prismatic folded plates which is a special case of the non-prismatic folded plates. Tn this paper, the result of analysis of a folded plates with one box type uniform cross-section is presented. Each plate is made of composite laminates with fiber orientation of [ABBCAAB]$_r$, with A=-B=$45^{\circ}$, and C=$90^{\circ}$. The influence of the span to depth ratio is also studied. When this ratio is 5, the difference between the results of folded plate theory and beam theory is 1.66%. is 1.66%.

• Structural Engineering and Mechanics
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• 제25권4호
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• pp.405-421
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• 2007

A four-node hybrid stress element for analysing orthotropic folded plate structures is presented. The formulation is based on Hellinger-Reissner variational principle. The element is developed by combining a hybrid plane stress element and a hybrid plate element. The proposed element has six degree of freedom per node and permits an easy connection to other type of elements. An equilibrated stress field in each element and inter element compatible boundary displacement field are assumed independently. Static and free vibration analyses of folded plates are carried out on numerical examples to show that the validity and efficiency of the present element.

• 한국강구조학회 논문집
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• 제13권1호
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• pp.41-52
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• 2001

본 연구에서는 복합재료로 구성된 구조물로서 박스거더와 같이 임의의 각도로 연결된 절판을 유한대판법으로 해석하였다. 각 적층판의 강성으로부터 적분에 의하여 판두께 방향의 전체 강성을 구하고 최소 포텐샬 에너지 이론으로부터 구한 평형방정식에 대입하여 전체 강성매트릭스를 구하였다. 슬래브나 박스거더의 변위 함수는 횡 방향의 Hermite 다항식과 종 방향의 조화함수의 결합으로 가정하였다. 종 방향 조화함수는 단부의 경계조건을 만족시키는 함수를 사용하였다. 해석시간의 단축 및 모델링이 쉽다는 장점을 가진 유한대판법은 복합적층 재료로 구성된 박스거더와 같은 절판해석의 경우에도 매우 정확한 해를 얻을 수 있다.

• 한국전산구조공학회논문집
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• 제20권1호
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• pp.29-37
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• 2007

본 연구에서는 3절점 요소와 4절점 요소를 가지는 비등방성 절판 구조물의 처짐 해석을 수행한다. 절판 구조물을 해석할 때 4절점 요소뿐만 아니라 3절점 요소의 사용이 필요한 경우가 발생하게 된다 그러나 3절점 요소를 사용하는 것은 간단하지 않다. 그러므로 본 연구에서 사용한 3절점 요소는 4절점 요소에서 절점을 감소시키는 방법을 사용하여 계산 과정의 편의성과 3절점 요소의 사용으로 인한 복잡성을 피할 수 있다. 이러한 방법을 고차 전단변형이론에 적용하기 위하여 Lagrangian 보간함수만을 사용한다. 또한 해석과정의 편의성 및 정확성을 위하여 면내회전각 자유도를 도입한다. 특히 본 논문에서는 3절점 및 4절점 요소의 사용에 의한 비등방성 복합적층 절판 구조물의 거동 특성을 분석하며 이에 대한 영향을 다양한 매개변수를 통하여 상세히 규명하고자 한다.

• 한국전산구조공학회논문집
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• 제19권3호
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• pp.223-231
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• 2006

본 연구에서는 복합적층 절판 구조물을 고차 전단변형이론을 이용하여 길이변화에 의한 거동 특성을 해석한다. 고차 전단변형이론을 적용하기 위하여 잘 알려진 Lagrangian 및 Hermite 보간함수를 병용한 방법은 다소 복잡하고 4절점 요소에만 적용할 수 있으며, 3절점 요소에 적용할 경우 매우 복잡하게 된다. 이러한 단점 및 복잡성을 피하기 위하여 Lagrangian 보간함수만을 사용한 고차 전단변형이론을 이용하며 복합적층 절판 구조물의 해석과정의 편의성 및 정확성을 위하여 면내 회전각 자유도를 추가한다. 그러므로 한 요소 당 4개의 절점이 있으며, 한 절점 당 10개의 자유도를 가지게 된다. 기존의 절판 구조물은 길이 변화에 대한 영향을 고려한 경우가 적으므로 본 연구에서는 이를 중심 변수로 설정하여 다양한 매개변수 연구를 수행한다. 본 연구에서는 길이 변화에 따라 예측하기 힘든 복잡한 거동을 보이는 복합적층 절판 구조물의 거동특성을 분석하여 합리적인 설계가 가능하고자 한다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(I)
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• pp.709-714
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• 2002

Recently, the applications of corrugated plates(or folded plates) are increasing due to economic and structural advantages in certain situations. And, because of the higher strength of corrugated plates than flat plates, the usage of the corrugated plates is increasing. So there are many necessities for specifications of corrugated plates. For flat plates, there are many design details in almost specifications. However, there are no detail design guides such as shear strength except the bending strength and the normal strength. So, it is difficult for engineers to design structures consist of corrugated plates. Therefore, a provision is necessary for engineers to refer for designing corrugated plates. The conclusion of this study shows a formula that helps to determine the shear strength of corrugated plates under various geometric conditions ; the size of corrugation ; the curvature of corrugation and ; the thickness of the corrugated plate. Also, it shows that corrugated plates have higher shear buckling strength than flat plates.

• Steel and Composite Structures
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• 제46권3호
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• pp.319-334
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• 2023

Localizing damages is an essential task to monitor the health of the structures since they may not be able to operate anymore. Among the damage detection techniques, non-destructive methods are considerably more preferred than destructive methods since damage can be located without affecting the structural integrity. However, these methods have several drawbacks in terms of detecting abilities, time consumption, cost, and hardware or software requirements. Employing artificial intelligence techniques could overcome such issues and could provide a powerful damage detection model if the technique is utilized correctly. In this study, the crack localization in flat and folded plate structures has been conducted by employing a Backpropagated Artificial Neural Network (BPANN). For this purpose, cracks with 18 different dimensions in thin, flat, and folded structures having 15⁰, 30⁰, 45⁰, and 60⁰ folding angle have been modeled and subjected to free vibration analysis by employing the Classical Plate Theory with Finite Element Method. A Four-nodded quadrilateral element having six degrees of freedom has been considered to represent those structures mathematically. The first ten natural frequencies have been obtained regarding healthy and cracked structures. To localize the crack, the ratios of the frequencies of the cracked flat and folded structures to those of healthy ones have been taken into account. Those ratios have been given to BPANN as the input variables, while the crack locations have been considered as the output variables. A total of 500 crack locations have been regarded within the dataset obtained from the results of the free vibration analysis. To build the best intelligent model, a feature search has been conducted for BAPNN regarding activation function, the number of hidden layers, and the number of hidden neurons. Regarding the analysis results, it is concluded that the BPANN is able to localize the cracks with an average accuracy of 95.12%.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 봄 학술발표회 논문집
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• pp.317-324
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• 1998

A nonlinear anile element formulation of flat shell elements with drilling d.o.f, is presented for the geometrical nonlinear analysis of thin-walled structures. The shell element to be applied in finite element analysis was developed by combining a membrane element named as CLM with drilling rotation d.o.f, and plate bending element. The combined shell element possesses six degrees of freedom per node. The element showed the excellent performance in the linear analysis of the folded plate structures, in which the normal rotational rigidity of folded plates is considered, therefore, using this element geometrical nonlinear analysis of those structures is fulfilled in this study. An incremental total Larangian approach is adopted through out in which displacements are referred to the original configuration. Comparing the results with those of other researches shows the performance of this element and a folded plate structure is analyzed as an example.