• Journal of Korean Society of Steel Construction
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• v.19 no.5
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• pp.539-548
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• 2007

This paper deals with flexural-torsional free vibrations of the circular strip foundation with the variable breadth on Pasternak soil. The cross-section of the strip foundation is chosen as the rectangular one with the constant thickness and variable breadth, which is symmetrical about the mid-arc. Also, the foundation that supports the circular strip is modeled as the Pasternak soil with the shear layer. Ordinary differential equations accompanying the boundary conditions are derived. In the governing equations, the transverse, rotatory and torsional inertias are included. These equations are solved numerically and four lowest frequencies are obtained. In the numerical results, the effects of foundation parameters on frequencies are extensively investigated. It is expected that the theories and numerical results of this study can be used in the dynamic design of strip foundations.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1A
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• pp.19-30
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• 2009

The primary objective of the present study was to attempt to quantify the effect of the existing codes for CFT composite section on initial section flexural stiffness, based on the measured vibration frequency of CFT truss girders. The formulae for the initial flexural stiffness of the composite sections in the different codes are compared with the free vibration test results. The results of the free vibration test on the CFT truss girders are in good agreement with the analysis results when used in ACI formulae. The free vibration analysis of CFT truss girders for different f/L ratios was conducted to determine how the natural frequency of the CFT truss girder is affected by different f/L ratios. The presence of the f/L ratios in CFT truss girders alters its frequencies of vibration because of the global stiffness of the CFT girders. The frequency in horizontal modes decreases as the f/L ratio increases. However, the frequency in vertical modes increases as the f/L ratio increases.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.1
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• pp.9-20
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• 1999

An accurate method is presented for flexural vibrations of rhombic plates having all combinations of clamped and free edge conditions. The prime focus here is that the analysis explicitly considers the bending stress singularities that occur in the two opposite, clamped-free corners having obtuse angles of the rhombic plates. Accurate non-dimensional frequencies and normalized contours of the vibratory transverse displacement are presented for rhombic plates having a large enough obtuse angle of 165$^{\circ}$, so that a significant influence of clamped-free corner stress singularities may be understood.

• Computational Structural Engineering
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• v.11 no.4
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• pp.275-286
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• 1998

본 논문은 고정, 단순, 또는 자유 연단 조건의 네 가지의 다른 조합을 갖는 마름모꼴형 평판의 자유진동 데이터를 처음으로 제시한 연구이다. 본 논문의 주된 관점은 마름모꼴 형 평판 둔각모서리의 휨응력의 특이도를 엄밀히 고려하여 해석하는 것이다. Ritz 방법을 이용하여 수직진동변위를 두 가지 적합 함수식으로 가정하였다. 힌지와 고정, 자유와 고정, 또한 힌지와 자유인 모서리 응력 특이도의 중대한 영향력이 이해될 수 있도록 충분히 큰 1650 둔각모서리를 갖는 마름모꼴형 평판에 대하여 엄밀한 무차원 진동수와 수직변동변위의 전형적인 등고선을 제시하였다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.9
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• pp.835-846
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• 2007

This paper deals with the flexural free vibrations of circular strip foundation with the variable breadth on Pasternak soil. The breadth of strip varies with the linear functional fashion, which is symmetric about the mid-arc. Differential equations governing flexural free vibrations of such strip foundation are derived, in which the elastic soil with the shear layer, i.e. Pasternak soil, is considered. Effects of the rotatory and shear deformation are included in the governing equations. Differential equations are numerically solved to calculate the natural frequencies and mode shapes. In the numerical examples, the hinged-hinged, hinged-clamped and clamped-clamped end constraints are considered. Four lowest frequency parameters accompanied with their corresponding mode shapes are reported and parametric studies between frequency parameters and various system parameters are investigated.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.1 s.53
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• pp.125-134
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• 2009

This paper deals with the free vibrations of circular strip foundations which have uniform solid rectangular cross-section. The ground which supports circular strips was modeled as the two parameter elastic foundation. Differential equations governing the flexural-torsional free vibrations of circular strips supported by such foundation were derived, and solved numerically for obtaining the natural frequencies and mode shapes. Boundary condition of free-free ends was considered for numerical examples. Four lowest natural frequencies according to the variations of five system parameters i.e. subtended angle, depth ratio, contact ratio, elasticity ratio and soil parameter are reported in the non-dimensional forms. Also, typical mode shapes of both deformations and stress resultants are presented in the figures. Experiment was conducted for validating the theory developed in this study.

• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.4
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• pp.217-223
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• 1998

본 논문에서는 원형연단이 단순지지 되어 있을 때 단순과 자유의 방사연단 조건을 갖는 부채꼴형 평판의 휨진동에 대한 엄밀한 해석방법을 제시한다. Ritz방법을 이용하여 수직진동변위를 두가지 적합 함수식으로 가정하였다. 이러한 두가지의 적합 함수식은 (1) 수학적으로 완전한 대수삼각다항함수와, (2) 둔각 모서리에서의 휨모멘트 특이도를 고려하는 모서리함수로 구성되어있다. 본 연구에서는 방사연단의 둔각 모서리를 이루는 부채꼴형 각도의 범위에 따른 엄밀한 진동수 및 수직진동 변위의 전형적인 등고선을 제시하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1992.06a
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• pp.137-140
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• 1992

실내 바닥슬래브의 휨진동에 의한 음향방사문제에 대하여 유한요소법을 적용하여 검토하였다. 단순한 형상의 판이 휨진동하여 자유공간에 음을 방사하는 문제에 대해서는 이론적인 해를 구할 수 있으나, 임의형상의 판이 휨진동하여 실내에 음을 방사하는 문제에 대해서는 검토되지 않았다. 따라서 본 연구에서는 이와같은 문제를 단순화한 해석법으로서 먼저 유한요소법을 이용하여 판의 휨진동에 대한 고유모드의 상대변위를 구하고, 다음 상대변위를 진동속도로 변환한 결과를 입력조건으로 하여 유한요소법에 의한 3차원 음장해석을 하였다. 그 결과 실내 바닥슬래브의 휨진동에 의한 음향방사파워는 슬래브의 진동모드, 실내음향모드 및 벽흡음율 등의 조건에 따라 크게 변화된다는 것을 확인하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.352-355
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• 2007

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1990.10a
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• pp.199-203
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• 1990

본 연구에서는 일반적인 형상을 갖는 회전축에서 축 방향 하중과 토오크를 각각 또는 동시에 고려할 수 있는 전달 행렬을 수식화하였고, 이에 의한 진 동 특성을 해석하기 위하여 강제진동 해석 및 자유진동 해석을 수행하였으 며, 해석결과에 대한 신빙성을 얻기 위하여 과도진동 해석 및 이산화 FFT를 통하여 검산기능을 추가하였다. 그리고 전달 행렬법에 새로운 고유치 수치해 법과 수치 적분법의 적용을 통하여 `수렴성과 안정성을 개선하였다.