• Steel and Composite Structures
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• 제10권3호
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• pp.223-243
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• 2010

This paper reports recent developments concerning the application of Generalised Beam Theory (GBT) to the structural analysis of steel-concrete composite bridges. The potential of GBT-based semi-analytical or finite element-based analyses in this field is illustrated/demonstrated by showing that both accurate and computationally efficient solutions may be achieved for a wide range of structural problems, namely those associated with the bridge (i) linear (first-order) static, (ii) vibration and (iii) lateral-torsional-distortional buckling behaviours. Several illustrative examples are presented, which concern bridges with two distinct cross-sections: (i) twin box girder and (ii) twin I-girder. Allowance is also made for the presence of discrete box diaphragms and both shear lag and shear connection flexibility effects.

• Advances in aircraft and spacecraft science
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• 제3권1호
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• pp.45-59
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• 2016

In this paper, the condensation method which is based on the Rayleigh-Ritz method, is described for the free vibration analysis of axially loaded slightly curved beams subject to partial axial restraints. If the longitudinal inertia is neglected, some of the Rayleigh-Ritz minimization equations are independent of the frequency. These equations can be used to formulate a relationship between the weighting coefficients associated with the lateral and longitudinal displacements, which leads to "connection coefficient matrix". Once this matrix is formed, it is then substituted into the remaining Rayleigh-Ritz equations to obtain an eigenvalue equation with a reduced matrix size. This method has been applied to simply supported and partially clamped beams with three different shapes of imperfection. The results indicate that for small imperfections resembling the fundamental vibration mode, the sum of the square of the fundamental natural and a non-dimensional axial load ratio normalized with respect to the fundamental critical load is approximately proportional to the square of the central displacement.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.923-926
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• 2007

In this paper, the vibration of a rotating shaft with a thin rigid disk is considered. It is assumed that the shaft has uniform, circular cross-section. Based on the Timoshenko-beam theory, the transverse displacements and slops in two lateral directions, the axial displacement, and the torsional deformation are considered. A spectral element model is developed by using the variation method for the vibration analysis of the rotating shaft with a thin rigid disk, which is modeled by two shaft elements and a thin rigid disk element. The result of vibration analysis by finite element method is compared to the result of this research.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.826-830
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• 2008

In this paper, the vibration of a rotating shaft with a thin rigid disk on bearing supports is considered. It is assumed that the shaft has uniform, circular cross-section. Based on the Timoshenko-beam theory, the transverse displacements and slops in two lateral directions, the axial displacement, and the torsional deformation are considered. And flexible supports are used to analyse the bearings. A spectral element model is developed for the vibration analysis of the rotating shaft with a thin rigid disk, which is modeled by two shaft elements and a thin rigid disk element. The result of vibration analysis by finite element method is compared to the result of this research.

• 소음진동
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• 제9권2호
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• pp.331-339
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• 1999

This paper presents the simplified formulas for calculating the fundamental frequencies of the cantilevered bellows in the axial and lateral directions. The frequencies of the bellow are evaluated based on analogies with those of the beam. It is shown that the results calculated by the simplified formulas are in good agreement with those obtained from FEM analysis and the experiment.

• 한국소음진동공학회논문집
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• 제15권5호
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• pp.586-594
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• 2005

In this paper, we studied about the effects of the rotating cantilever pipe conveying fluid with a moving mass. The influences of a rotating angular velocity, the velocity of fluid flow and moving mass on the dynamic behavior of a cantilever pipe have been studied by the numerical method. The equation of motion is derived by using the Lagrange's equation. The cantilever pipe is modeled by the Euler-Bernoulli beam theory. When the velocity of a moving mass is constant, the lateral tip-displacement of a cantilever pipe is proportional to the moving mass and the angular velocity. In the steady state, the lateral tip-displacement of a cantilever pipe is more sensitive to the velocity of fluid than the angular velocity, and the axial deflection of a cantilever pipe is more sensitive to the effect of a angular velocity. Totally, as the moving mass is increased, the frequency of a cantilever pipe is decreased in steady state.

• Coupled systems mechanics
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• 제11권6호
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• pp.485-504
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• 2022

This paper presents nonlinear oscillations of a carbon nanotube reinforced composite beam subjected to lateral harmonic load with damping effect based on the modified couple stress theory. As reinforcing phase, three different types of single walled carbon nanotubes distribution are considered through the thickness in polymeric matrix. The non-linear strain-displacement relationship is considered in the von Kármán nonlinearity. The governing nonlinear dynamic equation is derived with using of Hamilton's principle.The Galerkin's decomposition technique is utilized to discretize the governing nonlinear partial differential equation to nonlinear ordinary differential equation and then is solved by using of multiple time scale method. The frequency response equation and the forced vibration response of the system are obtained. Effects of patterns of reinforcement, volume fraction, excitation force and the length scale parameter on the nonlinear responses of the carbon nanotube reinforced composite beam are investigated.

• International Journal of Railway
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• 제3권3호
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• pp.83-89
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• 2010

This paper attempts to extract the fundamental dynamic properties, i.e. natural frequencies, damping ratios of the 48 m-long, $20^{\circ}$ skewed real bridge with PSC girders wrapped by a steel plate. The forced vibration test is achieved by mounting 12 Hz-capacity of artificial oscillator on the top of bridge deck. The acceleration histories at the 9 different locations of deck surface are recorded using accelerometors. From this full-scaled vibration test, the two possible resonance frequencies are detected at 2.38 Hz and 9.86 Hz of the skewed bridge deck by sweeping a beating frequency up to 12 Hz. The absolute acceleration/energy exhibits much higher in case of higher-order twist mode, 9.86 Hz due to the skewness of bridge deck which leads asymmetric situation of vibration. This implies the test bridge is under swinging vertically in fundamental flexure mode while the bridge is also flickered up and down laterally at 9.86 Hz. This is probably by asymmetric geometry of skewed deck. A detailed 3D beam-shell bridge models using finite elements are performed under a series of train loads for modal dynamic analyses. Thereby, the effect of skewness is examined to clarify the lateral flickering caused by asymmetrical geometry of bridge deck.

• 한국전산구조공학회논문집
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• 제23권1호
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• pp.73-80
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• 2010

건축물의 풍진동은 건축물의 사용성평가에 중요한 구조설계 요인 중 하나이다. 신뢰성있는 풍하중 및 풍진동을 구하기 위해서는 정확한 고유주기의 예측이 필요하며 이러한 고유주기에 오차가 있을 경우 하중을 과대 또는 과소평가하게 되는 문제를 유발한다. 본 논문에서는 최근 본격적으로 증가하고 있는 초고층 무량판 구조시스템의 건축물에 대하여 계측을 통한 횡강성 산정식의 유효성을 검정하였다. 이를 위하여 최근 건설된 초고층 무량판 구조시스템이 적용된 3개의 건물에 대하여 계측 결과와 해석 모델의 고유주기를 비교 분석하였다. 이때, 무량판 구조물의 횡강성에 영향을 미치는 요인들에 대하여 각 케이스별로 해석을 수행하였으며, 특히 일반적으로 사용되고 있는 콘크리트의 할선탄성계수와 동탄성계수가 적용 되었을 때의 구조물의 고유주기 변화를 비교하였다. 그 결과 풍진동에 의한 건물의 변형률은 매우 적기 때문에 할선탄성계수의 적용보다는 동탄성계수의 적용이 보다 정확한 해석의 결과를 가져올 것으로 판단된다.

• 한국광학회지
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• 제8권3호
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• pp.189-193
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• 1997

광 pick-up용 비구면 대물 렌즈는 컴퓨터와 멀티미디어 기기 등의 발달로 수요가 급증하고 있으며 사출성형에 의하여 대량 생산되고 있다. 광 pick-up용 비구면 대물 렌즈의 생산성 향상을 위해서는 생산공정중의 전수검사를 요구하며 이는 측정환경에 강인한 측정기를 필요로 하고 있다. 본 연구에서는 생산공정중에 광 pick-up용 비구면 대물 렌즈를 측정할 수 있는 개선된 층밀리기 간섭계를 제안하고자 한다. 본 층밀리기 간섭계는 3개의 직각 프리즘과 1개의 광분할 코팅된 프리즘으로 구성되며 index matching oil에 의하여 상대이동이 가능하도록 조합되어 있다. 간섭무늬를 정확히 분석하기 위한 위상천이와 층밀림량의 조절은 프리즘 간의 상대 이동에 의하여 가능하며 이를 위한 구동 기구부를 제작하였다. 또한, 본 연구에서는 반복연산에 의한 일반 알고리즘을 도입하여 위상천이 시에 발생하는 index matching oil의 유막 두께변화에 의한 기준위상 오차를 보상하였다. 광 pick-up용 비구면 대물 렌즈의 수차량을 정량적으로 산출하기 위하여 Zernike 다항식 맞춤을 수행하였다. 본 간섭계는 측정환경에 매우 강인하며 방진과 밀폐가 없는 열악한 측정환경하에서 반복측정을 수행하였을 때 .lambda./100 이하의 반복능을 얻었다.