• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.4
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• pp.1-8
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• 1989

The main purpose of the present paper is to present both the fundamental frequency and some higher free vibration frequencies for circular arches with variable section, in which rotatory inertia is included. The differential equations are derived for the in-plan free vibration of elastic circular arches with variable section. These equations were solved numerically for the linear variable circular cross-section with clamped-clamped end constraint. As the numerical results, the four lowest nondimensional natural frequencies presented as functions of the nondimensional system parameters : the end moment of inertia to crown moment of inertia ratio, the slenderness ratio, and the opening angle. The effect of rotatory inertia on the nondimensional natural frequency is also reported.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.48-58
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• 2014

In this study, quasi-static according to the displacement-controlled (strain control) method tests on RC columns for seismic reinforcement performance in accordance with the provisions of the seismic design and construction before 1992 design code for highway bridges in korea. Used reinforcement that improves the performance of Inorganic Helical Bar, a kind of alloy steel, circular columns were tested outside the seismic reinforcing. In the experiment, fracture behavior, lateral load-displacement relation, ductility and energy assessment evaluation was performed through tests. The variables in experimental are section force of reinforcement, spiral reinforcement spacing, reinforcement method. Improved seismic performance and effect were confirmed through quasi-static test experiments. The results of study confirmed determination the appropriate size of reinforcement, reinforcement forces, spacing and selection of the type required, furthermore, not only mechanical reinforcement but also substitution of high-strength concrete reinforced with concrete cover improved seismic performance.

• Computational Structural Engineering
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• v.11 no.3
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• pp.155-164
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• 1998

이 논문은 변단면을 고려한 수평 곡선보의 자유진동에 관한 연구이다. 진동시 곡선보 요소에 작용하는 합응력과 관성력의 동적평형방정식을 이용하여 변단면 원호형 수평 곡선보의 자유진동을 지배하는 상미분방정식을 유도하였다. 이 미분방정식을 원형 단면을 갖는 선형변변단면에 적용하여 고유진동수, 진동형 및 합응력을 산출하였다. 수치 해석예에서는 양단고정 및 양단회전 곡선보를 채택하였으며, 수치해석 결과로서 고유진동수와 단면비, 세장비 및 중심각 사이의 관계를 그림에 나타내었다. 또한 실험실 규모의 실험을 통하여 본 연구결과의 타당성을 보였다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.84-87
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• 2009

본 논문에서는 최근 초고층 건축물에 많이 활용되어지는 기둥-가새 시스템인 다이아그리드 시스템을 활용하여 중저층 건축물에 적용가능성을 평가하였다. 본 시스템은 튜브구조의 형태로 횡력에 대한 저항력이 우수하며 중력하중과 황하중을 기초와 지반에 안전하게 하중을 전달한다. 다이아그리드는 경사기둥과 보를 반복적으로 삼각형 형태로 배치되어 중력하중을 받을 경우 수직부재는 압축력을 보는 인장력을 받게 된다. 경사기둥과 보를 연결하는 접합부는 H-형강으로 설계 시 제작이 복잡하고 외관이 좋지 않다. 하지만 원형강관을 사용 할 경우 복합하지 않은 형태로 설계가 가능하고 외관이 우수하기 때문에 외부에 노출이 가능해진다. 또한 원형강관은 개방형 단면 부재에 비해 압축좌굴과 비틀림에 대한 성능 등이 우수하여 구조적인 성능이 우수하다. 원형강관을 이용하여 다이아그리드 시스템이 고층 건축물 뿐만 아니라 중저층 건축물에도 적용 타당성을 검토하였으며 원형강관 접합부 설계는 한계상태설계법이 사용 된 KBC2008(안)을 이용하여 설계하였다.

• Journal of Korean Society of Steel Construction
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• v.20 no.5
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• pp.655-663
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• 2008

In this research, the fire resistance of Concrete-Filled Circular Steel Tube Columns (CFT) was evaluated by numerical analysis. As the materials of CFT columns, the steel of SPSR 400 grade and the concrete of 27.5MPa, 37.8MPa strengths were used. Significant parameters,such as concrete strength, axial load, and cross-sectional dimensions were determined. To verify the accuracy of the numerical analysis,the analysis results were compared with the former experiment results. The effect of the fire resistance time, axial load ratio, cross-sectional dimensions and concrete strength was evaluated by comparison with the fire resistance of the square CFT columns. This research showed that the structural behavior and fire resistance from the findings of numerical parametric studies showed a similarity to that of the experimental results. Therefore, this numerical analysis is reasonable in estimating the fire resistance of the circular CFT column.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.3
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• pp.175-184
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• 2002

Ground reaction curve is very useful information for estimating the installation time of the tunnel support. The ground reaction curve can be estimated by analytical closed form solutions derived in case of circular section and isotropic stress condition. The nature of the ground reaction, however, depends significantly on tunnel configurations. Nevertheless, few purely analytical and experimental studies of this problem due to tunnel configurations appear to have been carried out. Therefore, it is necessary to investigate the influence of tunnel configurations in order to use simply in practical design. This paper describes a numerical study for the intial elastic displacement in the ground reaction curve due to configuration of tunnel excavation. In order to evaluate the applicability of analytical closed form solution in practical design, the parametric studies were carried out by numerical analysis in elastic tunnel behaviour. In the studies, S value, namely configuration factor, defined as the ratio between tunnel height (b) and width (a), varies between 0.5 and 3.0, initial ground vertical stress varies between 5~30 MPa for each S values. The results indicated that the self-supportability of ground is larger in the ground having low S value. It, however, is suggested that the applicability of closed form solution may not be adequate to determine directly the installation time of the support and self-supportability of ground. It should be necessary to perform the additional numerical analysis.

• Journal of the Korean Geotechnical Society
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• v.18 no.6
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• pp.33-42
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• 2002

Ground reaction curve is a very important information for evaluating the side wall displacements and installation time of the tunnle support. The ground reaction curve can be estimated by analytical closed form solutions derived on the supposition of circular section and isotropic stress condition. The conditions of stress field and tunnel configurations, however, are quite different in practice. Therefore, it is necessary to investigate the effects of stress anisotropy and tunnel configurations in order to use simply in practical design. This paper describes a study of influence factors in the ground reaction curve. In order to evaluate the applicability of analytical closed form solution in practical design, two sets of parametric studies were carried out by numerical analysis in elastic tunnel behaviour: one set of studies investigated the influence of the K and the other set investigated the influence of the tunnel configurations such as circular and horse-shoe shape. In the studies, K value varies between 0.5 and 3.0, initial ground vertical stress varies between 5～30MPa far each K values. The results indicated that the self-supportability of ground is larger in the ground having lower K value. However, it is suggested that the applicability of closed form solution may not be adequate to determine directly the installation time of the support and self-supportability of ground. It is necessary to consider stress anisotropy and tunnel configurations.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.10 s.115
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• pp.1024-1035
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• 2006

A three-dimensional (3-D) method of analysis is presented for determining the free vibration frequencies and mode shapes of thick, complete (circumferentially closed), circular rings with an elliptical or circular cross-section. Displacement components $u_r,\;u_\theta\;and\;u_z$ in the radial, circumferential, and axial directions, respectively, are taken to be periodic in ${\theta}$ and in time, and algebraic polynomials in the r and z directions. Potential (strain) and kinetic energies of the circular rings are formulated, and upper bound values of the frequencies are obtained by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Convergence to four-digit exactitude is demonstrated for the first five frequencies of the rings. Novel numerical results are presented for the circular rings having an elliptical cross-section based upon 3-D theory. Comparisons are also made between the frequencies from the present 3-D Ritz method and ones obtained from thin and thick ring theories, experiments, and another 3-D method.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.807-819
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• 1989

Buckling and vibration of laminated non-circular cylindrical shells with constant thickness and simply supported boundary condition is considered. Governing equations are derived based on the Donnell and Flugge shell theory and Galerkin method is applied for the numerical analysis. Comparisons are made between present results and others. Variations of frequency parameter and buckling load parameter on the change of stacking angle, eccentricity parameter and shell theories are investigated. Conclusion of this study is as follows: (1) General solutions of buckling and vibration of laminated non-circular cylindrical shell are obtained. (2) Frequency parameter is decreased as the initial axial load is increased. (3) In general, frequency and buckling load parameter of laminated non-circular cylindrical shells are decreased as increasing of eccentricity parameter and stacking angle.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.175-178
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• 1999

원형단면을 갖는 수신용 하이드로폰과 같은 면적의 정사각형 단면을 가정하여, 상온의 증류수를 매질로 초음파 변환기에서 방사되는 음장의 공간적 분포를 모의실험하였다. 이러한 "정사각형 평면 근사 평균법(이후 평면 근사 평균법)"을 이용하여, x-축 주사, z-축 주사, xy-평면 주사 및 xz-평면 주사를 모의실험하여 실제 실험에서 나타날 수 있는 여러 가지 현상을 조사하였다. z-축 주사 모의 실험 결과는 Beissner의 이론과 비교하여 비교적 잘 일치하였다