• 한국지진공학회논문집
• /
• 제16권3호
• /
• pp.1-12
• /
• 2012

이 논문에서는 유체-구조물-지반의 상호작용을 고려한 해상풍력발전기의 지진응답해석법을 제시하였다. 풍력발전기는 tower와 그 정점에 집중된 질량으로 모델링 되었다. 이 tower는 유연한 해저지반에 기초하고 있는 튜브형 cantilever로 이상화하였다. Tower와 해수 간의 동적 상호작용, 기초와 지반간의 동적 상호작용이 고려된 유체-구조물-지반 연성계의 지배방정식은 부분구조법과 Rayleigh-Ritz방법에 의해서 유도되었다. 해수는 압축성 비점성 이상 유체로 이상화하였다. 해수로 포화된 층상지반에 놓인 footing의 동적 강성은 Thin Layer법에 의해서 계산하여 상부구조물 모델과 결합시켰다. 이 해석법을 해상풍력발전기 모델의 지진응답해석에 적용하였다. 해석 결과를 준거해와 비교해서 제안한 해석법의 타당성을 검증하였다. Tower의 유연성, 지반의 강성이 해상풍력발전기 지진거동에 미치는 영향을 분석하였다. 유체-구조물 상호작용과 지반-구조물 상호작용의 지진응답에 대한 상대적인 중요도를 비교 평가하였다.

• 대한조선학회논문집
• /
• 제30권2호
• /
• pp.141-154
• /
• 1993

본 논문에서는 주변 단순 지지된, 용접된 편면 보강판의 압축 최종 강도를 구하는 간략한 방법을 제안하고자 한다. 우선, 용접에 의한 변형 및 잔류응력과 같은 초기결함을 간략한 방법으로 추정하고, 이 초기결함이 존재하는 보강판의 붕괴 양식을 가정하여, 각 양식에 대해 최종 강도를 구하고, 여러 붕괴 하중에 때해 최소치를 택함으로 보강판의 붕괴 하중을 얻는다. 보강판이 최종 강도 상태에 달하기까지 붕괴 과정을 다음과 같이 가정한다. (1) 보강판의 전체 좌굴$\rightarrow$보강재의 굽힘에 의한 전체 붕괴 (2) 판재의 국부 좌굴$\rightarrow$판재의 국부 붕괴$\rightarrow$보강재의 전단면 항복에 의한 전체 붕괴 (3) 판재의 국부 좌굴$\rightarrow$보강재의 굽힘에 의한 전체 붕괴 (4) 판재의 국부 좌굴$\rightarrow$판재의 국부 붕괴$\rightarrow$보강재의 비틂 변형(tripping)에 의한 전체 붕괴 붕괴 하중 계산을 위해 Rayleigh-Ritz 법에 기초한 탄소성 대변형 해석을 수행하고, 소성 붕괴선을 가정한 소성 해석을 수행하여 탄성 해석선과 소성 해석선의 교점을 최종 강도로 택한다. 본 방법을 비선형 유한요소법과 비교해 보면 극히 짧은 계산 시간에 양호한 결과를 산출한다는 것을 알 수 있다. 본 방법에 의한 해석 결과를 통해 판재의 국부 거동에 미치는 보강재의 비틂 강성의 효과를 고찰하였고, 보강재의 굽힘에 의한 전체붕괴와 비틂 변형(tripping)에 의한 전체 붕괴의 기준이 되는 보강재의 형상을 제시할 수 있었다.

• 한국소음진동공학회논문집
• /
• 제18권10호
• /
• pp.1024-1032
• /
• 2008

The vibration characteristics of a rotating cantilever beam undergoing impulsive force are investigated using wavelet transformation. The transient response induced by the impulsive force and the rigid body motion of the beam are calculated using hybrid deformation variable modeling along with the Rayleigh-Ritz assumed mode methods. The vibration characteristics of the beam can be analyzed in time-frequency domain with the wavelet transform method. Therefore, the effects of the impulsive force on the transient vibration characteristics of the beam can be investigated more effectively.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2005년도 춘계학술대회논문집
• /
• pp.721-724
• /
• 2005

With the advantages of large vibration energy dissipation of structures, the granular materials are used as vibration and acoustic treatments. In this case of vibro acoustic controls, a finite dynamic strength of the solid component (frame) is an important design factor. The dynamic stiffness of hollow cylindrical beams containing porous and granular materials as damping treatment was measured. Using the Rayleigh-Ritz method, the effects of damping materials on the dynamic characteristics of beams were investigated. The results suggested that the acoustic structure Interaction between the frame and the structure enhances the dissipation of the vibration energy significantly. The same methods were applied also to vibration control of sandwich panels. By filling the cavities of honeycomb cores using unconsolidated granular materials, its sound transmission toss was improved significantly.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 추계학술대회논문집
• /
• pp.451-456
• /
• 2006

This paper is concerned with the dynamic modeling and controller design for a cylindrical shell equipped with MFC actuators. The dynamic model was derived by using Rayleigh-Ritz method based on Donnel-Mushtari shell theory. The actuator and sensors for the MFC actuator equations were derived based on pin-force model. The boundary conditions at both ends were assumed to be shear diaphragm. After calculating the natural vibration characteristics, the positive position feedback controller was designed to cope with the first two modes. To this end, the equations of motion were reduced to modal equations of motion by considering the modes of interest. The theoretical results show that vibrations can be successfully suppressed.

• 한국안전학회지
• /
• 제18권1호
• /
• pp.19-27
• /
• 2003

This paper presented an experimental modal analysis of clamped perforated rectangular plates submerged in water. The penetration of holes in the plates had a triangular pattern with P/D (pitch to diameter) 1.750, 2.125, 2.500, 3.000 and 3.750. The natural frequencies of the perforated plates in air were obtained by the Rayleigh-Ritz method and compared with the experimental results. Good agreement was obtained between the analytical solution and experimental result. The experimental results in water showed that the mode shapes are not sensitive to the depth of submergence. The natural frequencies were shown to decrease drastically once the perforated plates come in contact with water. However, the natural frequencies decrease with the depth of submergence until a certain depth is reached, and become the asymptotic values beyond this depth of submergence. The depth of submergence did not affect the damping ratio greatly.

• 한국산업안전학회:학술대회논문집
• /
• 한국안전학회 2000년도 추계 학술논문발표회 논문집
• /
• pp.17-26
• /
• 2000

The early investigators into the in-plane vibration of rings were Hoppe $Hoppe ^{1)}$ and $Love ^{2)}$. $Love ^{2)}$ Improved on Hoppe's theory by allowing for stretching of the ring. $Lamb ^{3)}$ investigated the statics of incomplete ring with various boundary conditions and the dynamics of an incomplete free-free ring of small curvature. Den $Hartog ^{4)}$ used the Rayleigh-Ritz method for finding the lowest natural frequency of circular arcs with simply supported or clamped ends and his work was extended by Volterra and $Morell ^{5)}$ for the vibrations of arches having center lines in the form of cycloids, catenaries or parabolas.(omitted)

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
• /
• pp.303-308
• /
• 2002

A governing differential equation (GDE) of PSC flexural member with constant eccentricity considering the long-term losses including concrete creep, shrinkage, and PS steel relaxation is derived based on the two approaches. The first approach utilizes the force and moment equilibrium equations derived based on the geometry of strains of the uniform and curvature strains while the second one utilizes the principle of minimum total potential energy formulation. The identity of the two GDE's is verified by comparing the coefficients consisting of the GDE's. The boundary conditions resulting from the functional analysis of the variational calculus are investigated. Rayleigh-Ritz method provides a way to get the explicit form of the continuous deflection function in which the total potential energy is minimized with respect to the unknown coefficients consisting of the trial functions. As a closure, the analytically calculated results are compared with the experiments and show good agreements.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2007년도 춘계학술대회논문집
• /
• pp.75-80
• /
• 2007

This paper is concerned with the dynamic modeling and controller design for a cylindrical shell equipped with MFC actuators. The dynamic model was derived by using Rayleigh-Ritz method based on Donnel-Mushtari shell theory. The actuator and sensors for the MFC actuator equations were derived based on pinforce model. The boundary conditions at both ends were assumed to be shear diaphragm. After calculating the natural vibration characteristics, the positive position feedback controller was designed to cope with the first two modes. To this end, the equations of motion were reduced to modal equations of motion by considering the modes of interest. The theoretical results show that vibrations can be successfully suppressed.

• Coupled systems mechanics
• /
• 제2권4호
• /
• pp.303-327
• /
• 2013

The coupled free vibration of flexible structures and on-board liquid in zero gravity space was analyzed, considering the spacecraft main body as a rigid mass, the flexible appendages as two elastic beams, and the on-board liquid as a "spring-mass" system. Using the Lagrangians of a rigid mass (spacecraft main body), "spring-mass" (liquid), and two beams (flexible appendages), as well as assuming symmetric motion of the system, we obtained the frequency equations of the coupled system by applying Rayleigh-Ritz method. Solving these frequency equations, which are governed by three system parameters, as an eigenvalue problem, we obtained the coupled natural frequencies and vibration modes. We define the parameter for evaluating the magnitudes of coupled motions of the added mass (liquid) and beam (appendages). It was found that when varying one system parameter, the frequency curves veer, vibration modes exchange, and the significant coupling occurs not in the region closest to the two frequency curves but in the two regions separate from that region.