• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.235-240
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• 1997

터널발파는 벤치발파와 달리 일반적으로 심발발파, 주변공발파, 조절발파를 적용하는 최외곽공 발파로 나눌 수 있는데, 본 연구에서는 심발공법별 터널발파의 진동특성을 자유면의 수를 고려하여 해석하였다. 또한 터널발파의 발파효율에 가장 큰 영향을 미치는 심발발파 발파공들간의 지연지차를 서로 달리하면서 시험발파를 수행하였다. 국내 고속전철 건설현장의 터널발파시 측정한 진동속도의 파형분석결과 1자유면 발파인 심발발파시 발생하는 발파진동이 2자유면 발파인 주변공 발파시 발생하는 발파진동보다 30% 이상 더 크게 나타났고, 조절발파용 화약을 사용한 최외곽공 발파의 경우는 주변공발파보다 20% 정도 작은 진동속도를 나타내었다. 심발공법별 비교에서는 SUPEX-Cut의 경우가 국내에서 가장 널리 사용되는 V-Cut에 비해 20-30% 정도 더 작은 진동속도를 나타내었다. 또한 심발공들을 동시에 발파한 경우와 각 발파공의 시차를 서로 다르게 한 경우의 심발 시험발파 결과를 분석한 결과, 발파공간의 발파시차를 60msec 이상으로 하였을 때, 각 발파공의 발파시 발생한 진동이 서로 중첩되는 것을 방지할 수 있는 것으로 나타났다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.273-279
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• 1995

본 연구에서는 증기발생기 튜브의 마모마손에 대한 평가 방법을 열수력해석, 자유진동해석, 비선형해석, 마모량예측 등의 과정을 통해 증기발생기튜브의 마모량과 수명을 예측하는 방법에 대해 알아보았다. 본 연구를 통해 얻어진 결론은 다음과 같다. 1) 증기발생기 비선형충격해석에서 사용되는 정확한 난류 여기진동가진 가진력의 확보가 정확한 마모치를 예측할 수 있고, 2) 마모치예상을 위한 수식의 사용시 튜브의 미끌림거리 over bar L값이 매우 주요한 변수임을 알 수 있었다. 3) 충격력과 마모치의 연관관계에 대한 정확한 정의가 본 연구에 사용된 Archard의 마모방정식 이외에 여러 가지가 있으나, 아직 이들에 대한 정보부족으로 더 많은 검토가 필요하다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.609-617
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• 2002

A three-dimensional(3-D) method of analysis is presented for determining the free vibration frequencies and mode shapes of thick, circular rings with isosceles trapezoidal and triangular cross-sections. Displacement components u/sub s/, u/sub z/, and u/sub θin the meridional, normal, and circumferential directions, respectively, are taken to be sinusoidal in time, periodic in θ, and algebraic polynomials in the ψ and z directions. Potential(strain) and kinetic energies of the circular ring are formulated, and upper bound values of the frequencies we obtained by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Novel numerical results are presented for the circular rings with isosceles trapezoidal and equilateral triangular cross-sections having completely free boundaries. Convergence to four-digit exactitude is demonstrated for the first five frequencies of the rings. The method is applicable to thin rings, as well as thick and very thick ones.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.3
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• pp.191-200
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• 2021

This paper deals with the boundary conditions of the stress resultants at the mid-arc for free vibration analyses of the arch. The considered arch is a horseshoe symmetric elliptic arch. The work dealing with the boundary conditions of the deflection at both ends of the arch has already been reported in the open literature. This revisited paper aims to study the suitability of the boundary conditions of the stress resultants at the mid-arc to be replaced by the boundary condition at both ends. In this study, the boundary conditions of the stress resultants at the mid-arc are newly derived based on the theory of the previous work, and natural frequencies and mode shapes are obtained using the new boundary conditions of the stress resultants. The numerical results of this paper confirm that the new boundary conditions have been validated according to previous studies and results of finite element ADINA.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6A
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• pp.827-833
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• 2008

This paper deals with the free vibrations of elastica shaped arches. The elastica shaped arches are formed by the post-buckled column whose arc length is always constant. The equations governing free, planar vibration of general arch in open literature are modified for applying the free vibrations of elastica shaped arch and solved numerically to obtain frequencies and mode shapes for hinged-hinged, clamped-hinged and clamped-clamped end constraints. The effects of rotatory inertia, rise ratio and slenderness ratio on natural frequencies are presented. The frequencies of elastica shaped arches are greater than those of parabolic shaped ones. Also, typical mode shapes are presented in figures.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.449-453
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• 2010

본 논문에서는 점성 및 감쇠가 있는 단자유도 구조물의 등가감쇠비를 효율적으로 구하는 방법을 제시하였다. 건물에 설치된 마찰감쇠기는 외력의 크기에 따라 정지와 운동의 상태를 반복하여 외부 입력에너지를 소산시키기 때문에 외력과 응답관계가 비선형이다. 마찰감쇠기가 설치된 단자유도 건물은 마찰감쇠기외에 점성감쇠가 동시에 존재하므로 해석적인 정해를 구하기가 어렵다. 등가감쇠비를 산정하기 위해서 첫째, 점성과 마찰감쇠가 있는 단자유도계 건물의 자유진동 정해를 통하여 변위응답과 가속도 응답특성을 분석하였다. 둘째, 자유진동의 경우 응답이 멈출 때까지 소산에너지식을 이용하여 등가점성감쇠비를 구하였다. 셋째, 조화가진 일 때는 수치해석을 통하여 마찰력비 $F_r$에 따른 응답 특성을 알아보았다. 넷째, 조화가진의 경우 에너지 균형식을 바탕으로 등가점성감쇠비를 유도하였다. 등가점성감쇠비는 변위응답비의 영향을 받으므로 응답을 알아야만 구할 수 있다. 건물 응답의 진동수 특성은 협소영역(narrow band)이므로 고유진동수에 의해 지배된다고 가정하여 등가점성감쇠비를 구하였다. 마지막으로, 유도한 자유진동과 조화가진의 등 가점성감쇠비를 이용한 등가선형운동방정식의 해를 비선형 수치해석 한 결과와 비교하여 검증하였다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.10
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• pp.821-827
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• 2003

The so-called boundary node method (or NDIF method) that was developed by the authors has been extended for free vibration analysis of arbitrarily shaped plates with free edges. Since the proposed method requires no interpolation functions. no integration Procedure is needed on boundary edges of the plates and only a small amount of numerical calculation is involved, compared with FEM and BEM. In order to explain tile reason why spurious eigenvalues are generated when the NDIF method is applied to free plates, the NDIF method has been considered for free vibration analysis of both a fixed string and a free beam. Finally, verification examples show that natural frequencies obtained by the present method agree well with those given by an exact method or a numerical method (ANSYS).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.3 s.120
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• pp.220-225
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• 2007

Free vibration analysis using the method of NDIF (non-dimensional dynamic influence function), which was developed by the author, is extended to arbitrarily shaped polygonal plates with free edges. Local Cartesian coordinate systems are employed to apply the free boundary condition to nodes distributed along the edges of the plate of interest. Furthermore, a new way for applying the free boundary condition to nodes located at corners of the plate is for the first time introduced by considering the phenomenon of stress concentration at the corners. Two case studies show that the proposed method is valid and accurate when the eigenvalues by the proposed method are compared to those by FEM(ANSYS).

• Journal of Korean Association for Spatial Structures
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• v.10 no.4
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• pp.123-132
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• 2010

To overcome the drawback of currently available curved beam theories having non-symmetric thin-walled cross sections, a curved beam theory based on centroid-shear center formulation is presented for the spatially coupled free vibration and elastic analyses. For this, the displacement field is expressed by introducing displacement parameters defined at the centroid and shear center axes, respectively. Next the elastic strain and kinetic energies considering the thickness-curvature effect and the rotary inertia of curved beam are rigorously derived by degenerating the energies of the elastic continuum to those of curved beam. In order to illustrate the validity and the accuracy of this study, FE solutions using the Hermitian curved beam elements are presented and compared with the results by centroid formulation, previous research and ABAQUS's shell elements.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.27 no.3
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• pp.217-223
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• 1991