• 한국지반신소재학회논문집
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• 제14권4호
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• pp.87-96
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• 2015

토목섬유(Geosynthetics)는 도로, 철도, 항만, 댐, 제방 등의 각종 토목구조물에 보강, 배수, 필터, 분리, 침식방지 등의 용도로 폭넓게 적용되고 있다. 특히 토목섬유는 보강토옹벽이나 사면/지반 보강 등을 위한 보강용도로서의 적용이 활발하며, 최근에는 성토체의 안정성과 시공성 및 경제성 향상을 도모하기 위해 성토지지말뚝 상부를 토목섬유로 보강하는 기법에 대한 연구가 진행되고 있다. 일반적으로 토목섬유 보강재를 사용한 토목구조물의 안정성 해석을 위하여 실내 모형실험이나 현장에 적용된 토목섬유에 스트레인게이지를 부착하여 토목섬유의 인장변형을 측정하는 방법을 사용하고 있다. 그러나, 토목섬유의 제조방법과 강성도 및 스트레인게이지 부착방법 등에 따라 측정된 인장변형률 값의 편차가 나타난다. 본 연구에서는 지오그리드와 직포, 부직포 등 3가지 형태의 토목섬유를 대상으로 스트레인게이지가 부착된 토목섬유에 대한 광폭인장강도시험을 수행하여 video extensometer를 이용하여 측정된 인장변위로부터 산정한 인장변형률과 스트레인게이지에 의해 측정된 인장변형률을 비교, 분석함으로써 스트레인게이지 실측값의 신뢰성을 평가하였다. 분석 결과, 스트레인게이지 실측값은 비교적 강성이 높은 지오그리드와 직포의 경우에는 신뢰도가 높으나, 강성이 작은 부직포의 경우에는 신뢰도가 매우 낮음을 알 수 있었다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 봄 학술발표회 논문집
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• pp.291-300
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• 1998

This paper demonstrates how ambient vibration measurements at a limited number of locations can be effectively utilized to estimate parameters of a finite element model of a large-scale structural system involving a large number of elements. System identification using ambient vibration measurements presents a challenge requiring the use of special identification techniques, which ran deal with very small magnitudes of ambient vibration contaminated by noise without the knowledge of input farces. In the present study, the modal parameters such as natural frequencies, damping ratios, and mode shapes of the structural system were estimated by means of appropriate system identification techniques including the random decrement method. Moreover, estimation of parameters such as the stiffness matrix of the finite element model from the system response measured by a limited number of sensors is another challenge. In this study, the system stiffness matrix was estimated by using the quadratic optimization involving the computed and measured modal strain energy of the system, with the aid of a sensitivity relationship between each element stiffness and the modal parameters established by the second order inverse modal perturbation theory. The finite element models thus identified represent the actual structural system very well, as their calculated dynamic characteristics satisfactorily matched the observed ones from the ambient vibration test performed on a large-scale structural system subjected primarily to ambient wind excitations. The dynamic models identified by this study will be used for design of an active mass damper system to be installed on this structure fer suppressing its wind vibration.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.326-329
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• 2005

In the development of sheet-handling .machinery, it is important to predict the static and dynamic behavior of the sheets with a high degree of reliability because the sheets are fed and stacked at suck a high speed flexible media behaves geometric nonlinearity of large displacement and small strain. In this paper, static analysis of flexible media are performed by FEM considering geometric nonlinearity. Linear stiffness matrix and geometric nonlinear stiffness matrix based m the updated Lagrangian approach are derived using $C^1$ beam element and numerical simulations are performed by Updated Newton-Raphson(UNR) method.

• Journal of Advanced Marine Engineering and Technology
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• 제14권4호
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• pp.46-56
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• 1990

Stress analysis of axi-symetric body with non-symetric loading and non-symetric given displacements is investigated in this paper using the finite element method. As the non-symetric load and non-symetric given displacements of axi-symetric body are generally periodic functions of angle .theta., the nodal forces and nodal displacements can be expanded in cosine and sine series, that is, Fourier series. Furthermore, using Euler's formula, the cosine and sine series can be converted into exponential series and it is prooved that the related calculus become more clear. Substituting the nodal displacements expanded in Fourier series into the strain components of cylindrical coordinates system, the element strains are expressed in series form and by the principal of virtual work, the element stiffness martix and element load vector are obtained for each order. It is also showed that if the non-symetric loads are even or odd functions of angle ${\theta}$ the stiffness matrix and load vector of the system are composed with only real numbers and relatively small capacity fo computer memory is enough for calculation.

• 한국해양공학회지
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• 제11권4호
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• pp.7-22
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• 1997

A finite element analysis is performed for lateral buckling problems on the basis of a geometrically nonlinear formulation for a beam with small elastic strain but with possibly large rotations. The total Lagrangian formulation for a general large deformation, which involves finite rotations, is chosen and the exponential map is used to treat finite rotations from the Eulerian point of view. For lateral buckling, the point of vanishing determinant of the resulting unsymmetric tangent stiffness is traced to examine its relationship to bifurcation points. It is found that the points of vanishing determinant is not corresponding to bifurcation points for large deformations in general, which suggests that the present unsymmetric tangent stiffness is not an exact first derivative of internal forces with respect to displacement. This is illustrated through several numerical examples and followed by appropriate discussion.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.388-391
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• 2006

In the development of sheet-handling machinery, it is important to predict the static and dynamic behavior of the sheets with a high degree of reliability because the sheets are fed and stacked at such a high speed. Flexible media behaves geometric nonlinearity of large displacement and small strain. In this paper, static and dynamic analyses of flexible media are performed by FEM considering geometric nonlinearity. Linear stiffness matrix and geometric nonlinear stiffness matrix based on the Co-rotational(CR) approach are derived and numerical simulations are performed by Updated Newton-Raphson(UNR) method and Newmark integration scheme.

• Steel and Composite Structures
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• 제4권2호
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• pp.113-132
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• 2004

Double skin composite element (DSCE) is a novel form of construction comprising two skins of profiled steel sheeting with an infill of concrete. DSCEs are thought to be applicable as shear or core walls in a building where they can resist in-plane loads. In this paper, the behaviour of DSCE subjected to combined bending and shear deformation is described. Small-scale model tests on DSCEs manufactured from micro-concrete and very thin sheeting were conducted to investigate the flexural and shear behaviour along with analytical analysis. The model tests provided information on the strength, stiffness, strain conditions and failure modes of DSCEs. Detailed development of analytical models for strength and stiffness and their performance validation by model tests are presented.

• 한국유체기계학회 논문집
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• 제16권3호
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• pp.5-9
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• 2013

In this study, operational vibration experiment and analysis have been conducted for the 4-blade small vertical-axis wind turbine (VAWT) including the effect of tower elastic behavior. Computational structural dynamics analysis method is applied to obtain Campbell diagram for the VAWT with elastic tower. An open type wind-tunnel is used to change and keep the wind velocity during the ground test. Equivalent elastic tower is used to support the VAWT so that the effect of elastic stiffness of the tower can be considered in the present vibration experiment. Various excitation conditions with wind loads are considered and the dominant operating vibration phenomena are physically investigated in detail.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.162-166
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• 2011

In railway, Tie supports rail and plays a role that distribute train load to the ballast. Also, Tie and ballast resist against external force and fix the track position. But, weakening resistance of ballast and tie cause vertical displacement of tie and track irregularity. For reinforcement of track stiffness and reduction of track irregularity, KORAIL has developed Multi Branch type tie(GLORY Tie) that reinforced resistance than general PCT and installed in order to test in the field. This study measured and analyzed lateral resistance of ballast, wheel load of rail, bending strain of rail foot, vertical displacement and vibration acceleration of tie in order to evaluate performance of Multi Branch type tie in the field. According to the results of test, Multi Branch tie is excellent than general tie about lateral resistance of ballast and vertical displacement of tie. And, gap of measurement value between Multi Branch type tie and general tie about wheel load of rail, bending strain of rail foot were very small.

• Coupled systems mechanics
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• 제11권5호
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• pp.373-387
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• 2022

In this paper,soil-structure interaction effects on the seismic response of multistory frame structure on raft foundation are numerically analyzed. The foundation soil profile is assumed to consists of a clay layer of variable thicknessresting on bedrock. Amodified plane-strain numerical model isformed in the software Plaxis, and both free vibration analysis, and earthquake analysis for a selected ground motion accelerogram are performed. The behavior of the structure is assumed to be linear elastic with Rayleigh viscous damping included. The behavior of the clay layer is modeled with a Hardening soil model with small strain stiffness. The computed results in terms of fundamental period and structural horizontal displacementsfor the case of fixed base and for different thicknesses of clay layer are presented, compared, and discussed.