• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1148-1158
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• 2005

This work reports results of our study on the dynamic responses of the buried pipelines both along the axial and the transverse directions under various boundary end conditions. We have considered three cases, i.e., the free ends, the fixed ends, and the fixed-free ends. We have studied the seismic responses of the buried pipelines with the various boundary end conditions both along the axial and the transverse direction. We have considered three cases, i.e., the free ends, the fixed ends, and the fixed-free ends for the axial direction, and three more cases including the guided ends, the simply supported ends, and the supported-guided ends for the transverse direction. The buried pipelines are modeled as beams on elastic foundation while the seismic waves as a ground displacement in the form of a sinusoidal wave. The natural frequency and its mode, and the effect of parameters have been interpreted in terms of free vibration. The natural frequency varies most significantly by the soil stiffness and the length of the buried pipelines in the case of free vibration, which increases with increasing soil stiffness and decreases with increasing length of the buried pipeline. Such a behavior appears most prominently along the axial rather than the transverse direction of the buried pipelines. The resulting frequencies and the mode shapes obtained from the free vibration for the various boundary end conditions of the pipelines have been utilized to derive the mathematical formulae for the displacements and the strains along the axial direction, and the displacements and the bending strains along the transverse direction in case of the forced vibration. The negligibly small difference of 6.2% between our result and that of Ogawa et. al. (2001) for the axial strain with a one second period confirms the accuracy of our approach in this study.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.1340-1347
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• 2006

Dynamic response of buried pipelines both in the axial and the transverse directions on concrete pipe and steel pipe, FRP pipe were investigated through a free vibration analysis. End boundary conditions considered herein consist of free ends, fixed ends, and fixed-free ends in the axial and the transverse direction. Guided ends, simply supported ends, and supported-guided ends were added to the transverse direction. The buried pipeline was regarded as a beam on an elastic foundation and the ground displacement of sinusoidal wave was applied to it. Natural frequencies and mode shapes were determined according to end boundary conditions. In addition, the effects of parameters on the natural frequency were evaluated. The natural frequency is affected most significantly by the soil stiffness and the length of the buried pipelines. The natural frequency increases as the soil stiffness increases while it decreases as the length of the buried pipeline increases. Such behavior appears to be dominant in the axial direction rather than in the transverse direction of the buried pipelines.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.117-120
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• 2007

This study deals with the free vibrations and buckling loads of column with clamped-spring ends and constant volume. The column has the regular polygon cross-section whose depth is varied with the linear functional fashion. The differential equation governing the free vibration of such column is derived in which the effect of axial load is included. The differential equation is solved numerically for calculating frequencies. By using the relationship between loads and frequencies, the buckling loads are also obtained.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.328-337
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• 2005

This work reports results of our study on the dynamic responses of the buried pipelines both along the axial and the transverse directions under various boundary end conditions. We have considered three cases, i.e., the free ends, the fixed ends, and the fixed-free ends for the axial direction, and three more cases including the guided ends, the simply supported ends, and the supported-guided ends for the transverse direction. In order to investigate the effect of the boundary end conditions for the dynamic responses of the buried pipeline, we have devised a computer program to find the solutions of the formulae on the dynamic responses (displacements, axial strains, and bending strains) under the various boundary end conditions considered in this study. The dynamic behavior of the buried pipelines for the forced vibration is found to exhibit two different forms, a transient response and a steady state response, depending on the time before and after the transfer of a seismic wave on the end of the buried pipeline. The former is identified by a slight change in its behavior before the sinusoidal-shaped seismic wave travels along the whole length of the pipeline whereas the latter by the complete form of a sinusoidal wave when the wave travels throughout the pipeline. The transient response becomes insignificant as the wave speed increases. We have observed a resonance when the mode wavelength matches the wavelength of the seismic wave, where the mode number(k) of resonance for the axial direction is found to be $\overline{\omega}/{\pi}V+1/2$ for the fixed-free ends, $\overline{\omega}/{\pi}V+1$ for the free ends, and $\overline{\omega}/{\pi}V$ for the fixed ends, respectively. By adding 10 more modes to the mode number(k) of resonance, we were able to study all the dynamic responses of the buried pipeline for the axial direction. On the other hand, we have not been able to observe a resonance in the analysis for the transverse direction, because the dynamic responses are found to vanish after the seventh mode. From the results of the dynamic responses at the many points of the pipeline, we have found that the responses appeared to be dependent critically on the boundary end conditions. Such effects are found to be most prominent especially for the maximum values of the displacement and the strain and its position.

• 화약ㆍ발파
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• 제22권3호
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• pp.13-26
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• 2004

본 연구는 건설현장에서 매설관의 경계조건에 따른 동적 거동에 대한 진동안전기준에 관한 연구이다. 경계조건은 양단자유이며, 축방향 및 축직각방향에 대한 거동을 조사하였다. 매설관은 탄성기초 위에 놓인 보요소로 모형화하였고, 지진파는 정현파 형태의 지반 변위로 적용하였다. 매설관의 고유진동수와 모드 형태 그리고 매개변수의 영향을 조사하기 위해 자유진동에 대한 해석을 수행하였다. 그리고 지진파에 대한 거동을 조사하기 위해 자유진동 해석을 통해 얻어진 고유진동수와 모드 형태를 이용하여 진동에 대한 수식을 유도하였으며, 진동안전기준치 5 cm/sec에 안전하였고 양단자유의 매설관에 대한 자유진동 및 강제진동시의 시간-변위곡선을 나타내기 위한 전산프로그램을 완성하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1990년도 봄 학술발표회 논문집
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• pp.12-17
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• 1990

Stepped bean with immovable ends for large amplitude of vibration including effects of longitudinal displacement, shear deformation and rotary inertia is investigated for free and forced vibration using finite element method. Modified harmonic force matrix is introduced for analysis of vibration with finite amplitude of the stepped beam under uniform hamonic loading and beam with nonuniform harmonic loading. Numerical examples of stepped beam with various support conditions are analysed for deflections and natural frequencies. Results show that the proposed method is valid and efficient.

• Structural Engineering and Mechanics
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• 제31권6호
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• pp.663-678
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• 2009

An exact solution is obtained for forced torsional vibration of a finite class 622 piezoelectric hollow cylinder with free-free ends subjected to dynamic shearing stress and time dependent electric potential at both internal and external surfaces. The solution is first expanded in axial direction with trigonometric series and the governing equations for the new variables about radial coordinate r and time t are derived with the aid of Fourier series expansion technique. By means of the superposition method and the separation of variables technique, the solution for torsional vibration is finally obtained. Natural frequencies and the transient torsional responses for finite class 622 piezoelectric hollow cylinder with free-free ends are computed and illustrated.

• 대한두개안면성형외과학회지
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• 제9권2호
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• pp.110-113
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• 2008

Purpose: The jejunal free flap is the most standard and reliable procedure of reconstruction of the circumferential pharyngoesophageal defect because it provides pliable, elastic, secreting mucosa and posses reliable vascular anatomy. In this report, the authors introduce the modification of jejunal free flap for decreasing the complications in fatty complicated patients. Method: After harvesting the jejunum with mesentery and mesenteric vessels, both ends of jejunum were excised remaining the mesenteric portion. The jejunal portion of this composite flap was placed to reconstruct esophagopharyngeal defect area and the mesenteric portion was used to obliterate the dead space at paratracheal region and to cover the vital structure and the vascular anastomotic region. Result: A 72 year-old man with recurrent hypopharyngeal cancer who had about 15 cm sized circumferential pharyngoesophageal defect after total pharyngectomy was reconstructed with jejunomesenteric composite free flap without any complications. Conclusion: The mesenteric flaps at both side of jejunomesenteric composite free flap provide the advantages that could obliterate dead space, that could provide cover for the vital cervical vascular structure in case of vascularity was compromised due to previous radiation therapy, and that could preserve as much vascularity at both ends of jejunal flap as possible.

• Structural Engineering and Mechanics
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• 제37권4호
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• pp.415-425
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• 2011

In this study, the homotopy perturbation method (HPM) is applied to free vibration analysis of beam on elastic foundation. This numerical method is applied on three different axially loaded cases, namely: 1) one end fixed, the other end simply supported; 2) both ends fixed and 3) both ends simply supported cases. Analytical solutions and frequency factors are evaluated for different ratios of axial load N acting on the beam to Euler buckling load, $N_r$. The application of HPM for the particular problem in this study gives results which are in excellent agreement with both analytical solutions and the variational iteration method (VIM) solutions for all the cases considered in this study and the differential transform method (DTM) results available in the literature for the fixed-pinned case.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.753-756
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• 2002

In this study, it is attempted to obtain the optimum size of holes in 15 square plate models where a hole exists on every quadrant of a plate, and to get eigenvalues by performing free vibration analysis far each model. Moreover, the specimen is produced from optimized square plate and eigenvalue of each plate is measured through the shocking load. And then the result is compared with that of finite element analysis. For free vibration analysis of the square plate, the boundary condition of finite element analysis and experiment is assumed as both ends support. From the results of this study, it is known that more stable structures can be designed by changing the natural frequency which is dependent on the location of holes and further studies are considered to be necessary for the basic design information.