• Journal of Advanced Marine Engineering and Technology
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• 제25권1호
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• pp.95-106
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• 2001

When the crankshaft of diesel engine has more than 3 throws, which are arranged in a different plane, its vibration induces coupled motions, especially the coupled torsional and axial vibration. Nowadays, the torsional vibration which is influenced rather weak than axial one, can be theoretically calculated fairly accurately, but theoretical calculation results of the axial vibration which is influenced strongly from torsional vibration is not so good. To get accurate calculation results of axial vibration, coupled axial-torsional vibration must be treated. In this investigation, coupled effects of vibration of diesel engine propulsion shafting are analyzed theoretically and some simple calculation methods are also studied. On this first report, effects of coupling on natural frequencies and their modes are mainly studied, setting the each mass in 4 degrees of freedom.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2000년도 춘계학술대회 논문집(Proceeding of the KOSME 2000 Spring Annual Meeting)
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• pp.60-71
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• 2000

When the crankshaft of Diesel engine has more than 3 throws which are arranged in a different plane its vibration induces coupled motions especially the coupled torsional and axial vibration. Nowadays the torsional vibration which is influenced rather weak than axial one can be theoretically calculated fairly accurately but theoretical calculation results of the axial vibration which is influenced strongly from torsional vibration is not so good. To get accurate calculation results of axial vibration coupled axial-torsional vibration must be treated. in this investigation coupled effects of vibration of Diesel engine propulsion shafting are analyzed theoretically and some more simple calculation methods are also studied. On this first report effects of coupling on natural frequencies and their modes are mainly studied setting the each mass in 4 degrees of freedom. later this problem may be studied again by setting each mass as 6 degrees of freedom.

• Advances in concrete construction
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• 제8권2호
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• pp.77-90
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• 2019

This paper aims to investigate vibration frequency decrease (vibration period elongation) of reinforced concrete (RC) structure with unreinforced infill wall and reinforced infill wall exposed to progressively increased artificial earthquake load on shaking table. For this purpose, two shaking table experiments were selected as a case study. Shaking table experiments were carried on 1:1 scaled prototype one bay one storey RC structure with infill walls. The purpose of this shaking table experiment sequence is to assess local behavior and progressive collapse mechanism. Frequency decrease and eigen-vector evolution are directly related to in-plane and out-of-plane bearing capacities of infill wall enclosure with reinforced concrete frame. Firstly, frequency decrease-damage relationship was evaluated on the base of experiment results. Then, frequency decrease and stiffness degradation were evaluated with applied Peak Ground Acceleration (PGA) by considering strength deterioration. Lastly, eigenvector evolution-local damage and eigenvector evolution-frequency decrease relationship was investigated. Five modes were considered while evaluating damage and frequency decrease of the tested specimens. The relationship between frequency decrease, stiffness degradation and damage level were presented while comparing with Unreinforced Brick Infill (URB) and Reinforced Infill wall with Bed Joint Reinforcement (BJR) on the base of natural vibration frequency.

• 한국공간구조학회논문집
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• 제22권1호
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• pp.33-40
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• 2022

When the center of stiffness and the center of mass of the structure differ under the seismic load, torsion is caused by eccentricity. In this study, an analysis model was modeled in which the positions of the core and the plane rotation axis of a 60-story torsional atypical structure with a plane rotation angle of 1 degree per floor were different. The structural behavior of the analysis model was analyzed, and the earthquake response behavior of the structure was analyzed based on the time history analysis results. As a result, as the eccentricity of the structure increased, the eccentricity response was amplified in the high-rise part, and the bending and torsional behavior responses were complex in the low-order vibration mode. As a result of the analysis, the maximum displacement and story drift ratio increased due to the torsional behavior. The maximum story shear force and the story absolute maximum acceleration showed similarities for each analysis model according to the shape of the vibration mode of the analysis model.

• Structural Engineering and Mechanics
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• 제59권3호
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• pp.403-430
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• 2016

This paper studies the dynamics of the lineal-located time-harmonic moving-with-constant-velocity load which acts on the hydro-elastic system consisting of the elastic plate, compressible viscous fluid - strip and rigid wall. The plane-strain state in the plate is considered and its motion is described by employing the exact equations of elastodynamics but the plane-parallel flow of the fluid is described by the linearized Navier-Stokes equations. It is assumed that the velocity and force vectors of the constituents are continuous on the contact plane between the plate and fluid, and impermeability conditions on the rigid wall are satisfied. Numerical results on the velocity and stress distributions on the interface plane are presented and discussed and the focus is on the influence of the effect caused by the interaction between oscillation and moving of the external load. During these discussions, the corresponding earlier results by the authors are used which were obtained in the cases where, on the system under consideration, only the oscillating or moving load acts. In particular, it is established that the magnitude of the aforementioned interaction depends significantly on the vibration phase of the system.

• 한국전산구조공학회논문집
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• 제20권4호
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• pp.417-425
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• 2007

곡선보(curved beam)의 회전관성(rotatory inertia) 및 전단변형(shear deformation)을 고려한 면외(out-of-plane) 자유진동을 해석하는데 미분구적법(DQM)을 이용하여 고정-고정 경계조건(boundary conditions)과 다양한 굽힘각(opening angles)에 따른 진동수(frequencies)를 계산하였다. DQM의 결과는 엄밀해(efact solution) 또는 다른 수치해석 결과와 비교하였으며, DQM은 적은 요소(grid points)를 사용하여 정확한 해석결과를 보여주었다.

• Structural Engineering and Mechanics
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• 제50권2호
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• pp.137-149
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• 2014

In this study, modal parameters such as natural frequencies, mode shapes and damping ratios of RC frames with low strength are determined for different construction stages using ambient vibration test. For this purpose full scaled, one bay and one story RC frames are produced and tested for plane, brick in-filled and brick in-filled with plaster conditions. Measurement time, frequency span and effective mode number are determined by considering similar studies and literature. To obtain experimental dynamic characteristics, Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification techniques are used together. It is shown that the ambient vibration measurements are enough to identify the most significant modes of RC frames. The results indicate that modal parameters change significantly depending on the construction stages. In addition, Infill walls increase stiffness and change the mode shapes of the RC frame. There is a good agreement between mode shapes obtained from brick in-filled and in-filled with plaster conditions. However, some differences are seen in plane frame, like expected. Dynamic characteristics should be verified using finite element analysis. Finally, inconsistency between experimental and analytical dynamic characteristics should be minimize by finite element model updating using some uncertain parameters such as material properties, boundary condition and section properties to reflect the current behavior of the RC frames.

• Structural Engineering and Mechanics
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• 제89권6호
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• pp.601-615
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• 2024

Effect of ring and straight stiffeners in the buckling as well as vibration characteristics of metal-ceramic functionally graded plates with cutout subjected to various uniaxial and localized in-plane compressive edge loadings was explored in the present work. In the current work, the distinguishing characteristics of metal and ceramic are merged in a single volume, and power law was used for estimating the material composition throughout thickness. Buckling and free vibration characteristics were studied initially for unstiffened Al/SiC functionally graded plates with cutout. Subsequently, the influence of cutout ratio on buckling load as well as natural frequency for different power law indices was discussed. The functionally graded plate was stiffened by three different stiffener patterns, namely; ring stiffener, straight stiffener, as well as a combination of the ring and the straight stiffener, to enhance the buckling as well as vibration characteristics. The effect of stiffener depth ratio for different stiffener patterns was also presented for functionally graded plates having different cutout sizes under various loading conditions. Such studies on functionally graded material have potential applications in a variety of technological fields including the aerospace and defense sectors.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1994년도 봄 학술발표회 논문집
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• pp.105-112
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• 1994

In a local vibration analysis of a large steel frame, a large eigenvalue problem results. Due to computer storage and the expense of a complete solution, it is desirable to minimize the size of the resulting matrices. A new and efficient method of local vibration analysis for large steel frames is presented. It reduces the order of dynamic matrices by dynamic condensation method. Examples are given for local vibration of a plane frame. Results are compared to the complete solution of the full eigenvalue problem.

• Steel and Composite Structures
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• 제23권6호
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• pp.737-746
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• 2017

In this paper the influence of aspect ratio, height ratio and material angle on static and free vibration behaviour of orthotropic elliptic paraboloid shells is studied by using a four-node hybrid stress finite element. The formulation of the element is based on Hellinger-Reissner variational principle. The element is developed by combining a hybrid plane stress element and a hybrid plate element. A parametric study is carried out for static and free vibration response of orthotropic elliptic paraboloid shells with respect to displacements, internal forces, fundamental frequencies and mode shapes by varying the aspect and height ratios, and material angle.