• 한국전산구조공학회논문집
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• 제16권4호
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• pp.439-450
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• 2003

근래에 들어서 경제적 및 계획적인 요구에 의하여 충고를 줄일 수 있는 이점을 가진 플랫플레이트 구조물이 많이 건설되고 있다. 구조기술자들은 실무에서 플랫플레이트 구조물을 해석하기 위하여 일반적으로 유효보폭모델을 사용한다. 그러나 유효보폭 모델을 적용하기가 어려운 경우에는 유한요소법을 사용할 필요가 있으며, 이때 바닥판의 정확한 거동을 예측하기 위해서는 세분한 유한요소 모델을 사용하는 것이 필요하다. 전체 구조물을 수많은 유한요소로 세분하여 모형화하면 막대한 해석시간과 컴퓨터 메모리가 필요하게 된다. 따라서 본 연구에서는 상당히 정확한 해석결과를 쉽게 얻을 수 있는 효율적인 해석기법을 제안한다. 제안된 해석기법은 행렬응축기법을 통하여 생성된 수퍼요소를 사용하며 수퍼요소 경계부분의 변형적합조건을 만족시키기 위하여 수퍼요소를 개발할 때 가상보를 도입한다. 본 연구에서는 슬래브의 탄성계수를 감소시킴으로서 유효보폭모델에서 사용되고 있는 강성저감을 고려하였다. 수많은 요소론 사용한 유한요소모델 및 유효보폭모델을 사용하여 여러 가지의 예제구조물에 대하여 정적해석과 동적해석을 수행하고 본 연구에서 제안된 해석방법에 의한 결과와 비교함으로써 제안된 방법의 효율성과 정확성을 검증하였다.

• 한국강구조학회 논문집
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• 제15권4호통권65호
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• pp.403-412
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• 2003

건축물의 바닥판에 대한 합성슬래브 시스템의 사용이 점차 확대되어 오피스 빌딩을 중심으로 널리 사용되고 있다. 최근에는 주상복합형 및 주거용 건물에 대한 확대 적용을 휘해 하부면이 평탄한 플랫 데크플레이트의 필요성이 대두됨에 따라 플랫 데크플레이트가 개발되고 있다. 또한 합성슬래브시스템의 바닥판 상부에 와이어메쉬 대신 일체형으로 생산되는 익스팬디드 메탈을 적용할 경우, 원가 절감, 공기 단축 효과도 기대할 수 있을 것이다. 본 연구에서는 익스팬디드 메탈을 와이어메쉬의 대체재로 사용하여 이를 하부면이 평탄한 플랫 데크플레이트와 결합시킨 신형식의 합성블래브시스템을 제안하였다. 총 12개의 시험체에 대한 실험을 통해 그 구조성능을 평가하고자 하였다. 실험 결과는 시험체의 최대내력과 파괴거동 등을 중심으로 요약하여 나타냈다.

• 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%.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.225-228
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• 2002

Supersonic jet impingement on a flat plate has been investigated to show the flow physics for different jet heights and to demonstrate the adequacy of the characteristics-based flux-difference Wavier-Stokes code Current study also compares the steady-state solutions obtained with variable CFL number for different grid spacing with the time-accurate unsteady solutions using the inner iterations, displaying a good agreement between the two sets of numerical solutions. The unsteady nature of wall fluctuations due to bouncing of the plate shock is also uncovered for high pressure ratios. The methodology is then applied to a complex vertical launcher system where the jet plume hits the bottom wail, deflects into the plenum and eventually exits through the vertical uptake. Flow structures within vertical launcher system are captured and solutions are partially verified against the flight test data. Present jet impingement study thus shows the usefulness of CFD in designing a complex structure and predicting flow behavior within such a system.

• 한국전산구조공학회논문집
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• 제23권6호
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• pp.715-726
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• 2010

In this paper, a comparative study of metallic and non-metallic stiffened plates under a lateral pressure load is performed using conventional statistically determinate and SQP(Sequential Quadratic Programming) optimisation approaches. Initially, a metallic flat-bar stiffened plate is exemplified from the superstructure of a marine vessel and, subsequently, its structural topology is varied as hat-section stiffened FRP(Fibre Reinforced Plastics) single skin plates and monocoque FRP sandwich plates having a PVC foam core. These proposed structural alternatives are analysed using elastic closed-form solutions and SQP optimisation method under stress and deflection limits obtained from practice to calculate and optimise geometry dimensions and weights. Results obtained from the comparative study provide useful information for marine designers especially at the preliminary design stage where various building materials and structural configurations are dealt with.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.237-240
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• 2002

In the present study, we perform LES of turbulent flow and temperature fields in a circular impinging jet at Re=5000 for two cases of H/D=2 and 6 (H denotes the distance between the jet exit and flat plate, and D does the diameter of the jet exit). In the case of H/D=2, the regular vortical structures observed in free jet do not exist because of the smaller distance than the potential core. The Nusselt number on the wall is largest at $r/D{\cong}10.67$ where vortex rings Impinge. At $r/D{\cong}1.5{\~}2.0$, the vortex rings induce the secondary vortices, resulting in a secondary peak in the Nusselt number there. In the case of H/D=6, the vortex rings change into three-dimensional vortical structures and the small-scale vortices impinge on the flat plate. The increase of turbulent intensity due to small-scale vortices results in the largest Nusselt number at the stagnation point.

• 한국항해학회지
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• 제20권1호
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• pp.47-58
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• 1996

The use of high tensile steel plates is increasing in the fabrication of ship and offshore structures. The main portion of ship structure is usually composed of stiffened plates. In these structures, plate buckling is one of the most important design criteria and buckling load may usually be obtained as an eigenvalue solution of the governing equations for the plate. To use the high tensile steel plate effectively, its thickness may become thin so that the occurrence of buckling is inevitable and design allowing plate buckling may be necessary. When the panel elastic buckling is allowed, it is necessary to get precise understandings about the post-buckling behaviour of thin plates. It is well known that a thin flat plate undergoes secondary buckling after initial buckling took place and the deflection of the initial buckling mode was developed. From this point of view, this paper discusses the post-buckling behaviour of thin plates under thrust including the secondary buckling phenomenon. Series of elastic large deflection analyses were performed on rectangular plates with aspect ratio 3.6 using the analytical method and the FEM.

• Steel and Composite Structures
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• 제35권1호
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• pp.43-59
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• 2020

In this study, free vibration analysis of laminated composite parabolic thick plate frames by using finite element method is introduced. Governing equations of an eigenvalue problem are obtained from First Order Shear Deformation Theory (FSDT). Finite element method is employed to obtain natural frequency values from the governing differential equations. The frames consist of two flat square plates and one singly curved plate. Parameters like radii of curvature, aspect ratio, ply orientation and boundary conditions are investigated to understand their effect on dynamic behavior of such a structure. In addition, multi-bay structures of such geometry with different stacking order are also taken into account. The composite frame structures are also modeled and simulated via ANSYS to verify the accuracy of the present study.

• 동력기계공학회지
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• 제6권4호
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• pp.36-42
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• 2002

In the structures of automobiles and ships which have engines for works, the vibration energies generated by the engines are transferred to dissipation parts through the structures which is welded and bolted with beams and plates. The vibration energies generated by resonance frequencies are the reasons of the resonance phenomena. To solve these problems, up to the present, we have studied to avoid the resonance, and add the higher damping characteristics. However, we need to understand the structural energy flows, to design the structures clearly which have the characteristic of welding. The object of this study is to make differences clear in the characteristics of structures which have some welded part on an homogenous flat plate. In this investigation, we study the flows of structural vibration energy experimently, and then, some knowledge for dynamic structural design is obtained.

• 한국공간구조학회지
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• 제13권4호
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• pp.22-27
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• 2013