• Journal of the Society of Naval Architects of Korea
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• v.32 no.3
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• pp.116-125
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• 1995

In ship and of offshore structures, there exist many local panels of various shapes having many kinds of attachments reducible to damped spring-mass systems. For the vibration analysis of panels, analytical methods such as Rayleight-Ritz method or the assumed mode method can be efficiently applied. There have been many studies on the vibration analysis of rectangular panels using the analytical methods but relatively few for arbitrary shape panels. An efficient formulation based on the assumed mode method is presented for the vibration analysis of an arbitrary quadrangular plate having concentrated masses, supporting springs such as pillars and spring-mass systems. In the formulation, the natural coordinate system is used for the efficient treatment of an arbitrary quadrangular shape. Through some numerical calculations, accuracy and efficiency of the presented method are shown.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.2
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• pp.85-95
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• 1996

An iterative Kantorovich method is presented for the vibration analysis of rectangular isotopic and orthotropic thick plates. Mindlin plate characteristic functions are derived in general forms by the Kantorovich method initially starting with Timoshenko beam functions consistent with the boundary conditions of the plate. Through numerical calculations of natural pairs, i.e. natural frequencies and corresponding modes, and dynamic responses of appropriate models, it has been confirmed that the presented method is superior to the Rayleigh-Ritz analysis or the FEM analysis in accuracy and computational efficiency.

• Journal of Korean Society of Steel Construction
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• v.15 no.2
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• pp.125-135
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• 2003

A 3-dimensional model of curved steel box girder bridges without diaphragm was presented. This model yielded results that were consistent with those of the parameter analysis using the BEF and Ritz methods. Se veralmodels with diaphragms were analyzed to estimate the appropriate diaphragm spacing. In case of 50m span, models A-10, A-20, A-30, B-10, B-20, and B-30 were found to have 5(8.3m), 7(6.25m), 8(5.5m), 4(10m), 6(7.1m), and 7(6.25m) diaphragms, respectively. In addition, a formula that presents the ratio of distortional stress to bending stresswas created from the results of the 3-dimensional FEM model analysis.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.1
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• pp.117-124
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• 1991

In this paper, a method to overcome inefficiency of the finite element method in the calculation of compressive strength of one-sided stiffened plates, is proposed. In this method the collapse modes of stiffened plates are assumed as follows. a) Overall buckling $\rightarrow$ Overall collapse b) Local buckling $\rightarrow$ Overall collapse c) Local buckling $\rightarrow$ Local collapse In each collapse mode, shape of deflection is assumed, and then elastic large deformation analysis based on the Rayleigh-Ritz method is carried out. One-sided stiffening effect is considered by taking into account of the moment due to eccentricity. Plastic analysis by assuming hinge lines is also carried out. The ultimate strength of a stiffened plate is obtained as the point of intersection of the elastic analysis curve and the plastic one. From this study, it is concluded that the angles between the plastic hinge lines in plastic collapse mode are determined as the ones which give the minimum collapse load, and these angles are different from the ones assumed in the previous studies. Minimum stiffness ratios can also be calculated. Calculated results according to this method show good agreements with the results by the finite element method.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.2
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• pp.141-154
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• 1993

In this paper, a method to calculate the ultimate compressive strength of welded one-sided stiffened plates simply supported along all edges is proposed. At first initial imperfections such as distortions and residual stresses due to welding are predicted by using simplified methods. Then, the collapse modes of the stiffened plate are assumed and collapse loads for each mode are calculated. Among these loads, the lowest value is selected as the ultimate strength of the plate. Collapse modes are assumed as follows ; (1) Overall buckling of the stiffened plate$\rightarrow$Overall collapse due to stiffener bending (2) Local buckling of the plate part$\rightarrow$Local collapse of the plate part$\rightarrow$Overall collapse due to stiffener yielding (3) Local buckling of the plate part$\rightarrow$Overall collapse due to stiffener berthing (4) Local buckling of the plate part$\rightarrow$Local collapse of the plate part$\rightarrow$Overall collapse due to stiffener tripping. The elastic large deflection analysis based on the Rayleigh-Ritz method is carried out, and plastic analysis assuming hinge lines is also carried out. Collapse load is defined as the cross point of the two analysis curves. This method enables the utimate strength to be calculated with small computing time and a good accuracy. Using the present method, characteristics of the stiffener including torsional rigidity, bending and tripping can also be clarified.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.56-61
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• 1995

많은 공학자들은 기계 재료의 종류 및 형태에 따른 정적, 동적 특성 연구를 수행해 왔다. 특히 산업적으로 그 활용도가 높은 평판 재료에 대한 진동 특성 연구는 많이 이루어졌다. 최근에는 진동 특성을 해석하는 방법도 부분구조합성법, 감도해석법 등의 방법으로 연구가 활발히 이루어지고 있다. 한편 평판의 진동이 공기와 같은 매질로 상호 작용을 하며, 막힘이 없는 공간으로 음향을 방사하는 현상에 대한 연구도 이루어지고 있다. 그러나 평판 재료를 사용하여 기계 구조물을 제작하는 경우 많은 경우에 구조물간 결합에 의해 폐공간이 형성되고 이러한 폐공간에 의해 평판의 진동이 구조-음향 연성 현상이 발생되고, 이에 따라 평판의 진동 특성도 달라지게 된다. 이러한 구조-음향 연성에 대한 연구는 1978년 Wayne B.McDonald와 C.Kearney Barton, 1979년 R.Vaicatis에 의해 폐공간 내로의 음향 전달 현상을 연구하며 이루어졌다. 최근에 연구 동향은 이장명의 FEM과 BEM을 이용한 폐공간 내로의 음향 전달 현상을 연구하였고, V.B.Bokil에 의해 구조-음향 연성된 평판의 모드 해석 방법이 연구되었다. 한편 V.Martin에 의해 능동 소음 제어의 모델링을 좀더 정확히 하기 위해 구조 연성계를 고려한 연구도 수행되었다. 연구 결과 구조-음향 연성에 의한 평판의 고유진동수 변화를 구하였고 이 때에 경계조건을 만족하는 직교다항식을 이용한 Rayleigh-Ritz 방법을 이용하였다. 또한 이러한 해석은 실험과도 매우 잘 일치함을 알 수 있었다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.5
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• pp.439-450
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• 2008

In this study, the reduced system for the dynamic analysis is proposed and the selection criterion of the primary degrees of freedom is presented considering the relation between natural frequency and external loading frequency. A well-constructed reduced system can assure the accurate representation of the dynamic behavior under arbitrary dynamic loads. For selecting the primary degrees of freedom of the reduced system, we employ the robust two-level condensation scheme of which the reliability has been proven through previous study. In the numerical examples, the reliability of the dynamic analysis based on the reduced system is demonstrated through comparing with those of global system.

• Journal of Ocean Engineering and Technology
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• v.17 no.3 s.52
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• pp.21-26
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• 2003

An iteractive Kantorovich method is presented for the vibration analysis of rectangular orthotropic thick plates. Mindlin plate characteristic functions are derived in general forms using the Kantorovich method. Initially, Timoshenko beam functions consistent with the boundary conditions of the plate were used. Through numerical calculations of natural fairs of appropriate models, it has been confirmed that the method presented is superior to the Rayleigh-Ritz analysis or the finite element analysis in both accuracy and computational efficiency.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.6
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• pp.63-70
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• 1985

In this paper, the Unilateral Fin-line structure and the I-Plane structure are analysed by Rayleigh-Ritz variational method including the effect of conductor thickness. And a com-putcr-aided design program, CADUNI, is developed for microwave I-plane and Unilateral Fin-Line bandpass filters. Unilateral Fin-Line Filters are desigied at the center frequency of 10.5 GHz with guided bandwidth between 5% and 24.6%. Measured insertion loss is between 0.17 and 0.25 dB, and center frequency deviation is less than 0.2%. Experimental results are in good agree-ment with theory.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.3
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• pp.411-418
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• 1992

본 연구에서는 인장하중을 받는 균열이 없는 박판 시험편과 45˚경사균열시험 편의 고유진동수 측정을 위하여 레이저 홀로그래피법을 이용하여 진동모드 측정을 하 여 그 결과를 비교분석하는 실험방법을 택하였으며, 균열이 없는 박판에 대해서만 무 차원하중의 증가에 따른 고유 진동수의 변화관계를 실험치와 Ritz Method에 의한 유한 요소 해석치와 비교하였다.