• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.12 no.4
• /
• pp.81-93
• /
• 1992

Numerical modeling of problems having infinite and semi-infinite boundaries is studied using a coupled method of distinct elements and boundary elements. The regions which are restricted on stress concentration area of loading points, excavation surface, and geometric discontinuity in the underground structures, are modeled using distinct elements, while the infinite and semi-infinite regions are modeled using linear boundary elements. Linear boundary elements for infinite and semi-infinite region are respectively composed using the Kelvin's and the Melan's solution, respectively. For the completeness, the boundary element method, the distinct element, and the coupled method of distinct elements and boundary elements are studied independently. The coupled method is verified and is applied to underground structures of infinite and semi-infinite regions. Through the comparison of the results, it is concluded that the coupled analysis may be used for discontinuous underground structures in the effective manner.

• Proceedings of the KAIS Fall Conference
• /
• 2008.11a
• /
• pp.79-81
• /
• 2008

2차원균열을 포함하고 있는 무한체가 균일한 전단응력을 받고 있는 경우에 대한 복소응력함수를 기존의 응력함수를 이용하여 해석적으로 구하였다. 이는 등각사상과 정칙연속법에 의하여 구하였다. 결과는 극한의 경우에 대하여 검증하였으며 구한 복소응력함수는 맞는다는 것을 보여준다.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.21 no.1
• /
• pp.69-79
• /
• 2001

A volume integral equation method(VIEM) is applied for the effective analysis of elastic wave scattering problems in unbounded solids containing general anisotropic inclusions. It should be noted that this newly developed numerical method does not require the Green's function for anisotropic inclusions to solve this class of problems since only the Green's function for the unbounded isotropic matrix is Involved In their formulation for the analysis. nis new method can also be applied to general two-dimensional elastodynamic problems with arbitrary shapes and number of anisotropic inclusions. Through the analysis of plane elastodynamic problems in unbounded isotropic matrix with an orthotropic inclusion, it is established that this new method is very accurate and effective for solving plane elastic problems in unbounded solids containing general anisotropic inclusions.

• Journal of the Korean Institute of Gas
• /
• v.5 no.3 s.15
• /
• pp.51-54
• /
• 2001

지진 등과 같은 외부 진동하중에 의해 발생되는 구조물의 진동은 구조물의 독립적 거동뿐만 아니라 지반과 구조물 기초의 접촉면을 통해 상호 영향을 미치게 된다. 특히 LNG 저장탱크나 원자력발전소 등과 같이 대현 상부구조물의 경우 상호작용력은 크게 작용하게 된다. 본 연구에서는 상부 구조계의 단순화된 형태인 기초계의 동적거동을 파악하기 위해 주파수영역 경계요소법을 사용하여 수치적으로 연구하였다. 반무한체 상에 존재하는 무질량 강체 표면기초에 대해 반무한 기본해를 이용하여 동적거동이 고찰되었으며 기존의 해석결과와 비교, 검토하여 본 연구방법의 타당함을 입증하였다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.4 s.175
• /
• pp.1032-1038
• /
• 2000

The stress field in the body by tangential loading of a rectangular patch on a semi-infinite solid has been solved analytically using potential function. The validity of result of this study was proved by Saint-Venant's principle in the remote region and in the vicinity of the surface with superposition of point loads.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.34 no.4
• /
• pp.221-230
• /
• 2021

This paper proposes full waveform inversion (FWI) for estimating the physical properties of a layered half-space. An FWI solution is obtained using a genetic algorithm (GA), which is a well-known global optimization approach. The dynamic responses of a layered half-space subjected to a harmonic vertical disk load are measured and compared with those calculated using the estimated physical properties. The responses are calculated using the thin-layer method, which is accurate and efficient for layered media. Subsequently, a numerical model is constructed for a layered half-space using mid-point integrated finite elements and perfectly matched discrete layers. An objective function of the global optimization problem is defined as the L2-norm of the difference between the observed and estimated responses. A GA is used to minimize the objective function and obtain a solution for the FWI. The accuracy of the proposed approach is applied to various problems involving layered half-spaces. The results verify that the proposed FWI based on a GA is suitable for estimating the material properties of a layered half-space, even when the measured responses include measurement noise.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.36 no.3
• /
• pp.203-211
• /
• 2023

A Markov chain Monte Carlo (MCMC) simulation is proposed for probabilistic full waveform inversion (FWI) in a layered half-space. Dynamic responses on the half-space surface are estimated using the thin-layer method when a harmonic vertical force is applied. Subsequently, a posterior probability distribution function and the corresponding objective function are formulated to minimize the difference between estimations and observed data as well as that of model parameters from prior information. Based on the gradient of the objective function, a proposal distribution and an acceptance probability for MCMC samples are proposed. The proposed MCMC simulation is applied to several layered half-space examples. It is demonstrated that the proposed MCMC simulation for probabilistic FWI can estimate probabilistic material properties such as the shear-wave velocities of a layered half-space.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.12 no.3
• /
• pp.465-474
• /
• 1999

A recently developed numerical method based on a volume integral formulation is applied to calculate the accurate stress intensity factors at the crack tips in unbounded isotropic solids in the presence of multiple anisotropic inclusions and cracks subject to external loads. In this paper, a detailed analysis of the stress intensity factors are carried out for an unbounded isotropic matrix containing an orthotropic cylindrical inclusion and a crack. The accuracy and effectiveness of the new method are examined through comparison with results obtained from analytical method and finite element method using ANSYS. It is demonstrated that this new method is very accurate and effective for solving plane elastostatic problems in unbounded solids containing anisotropic inclusions and cracks.

• Composites Research
• /
• v.23 no.4
• /
• pp.7-13
• /
• 2010

A volume integral equation method (VIEM) is introduced for the solution of elastostatic problems in an unbounded isotropic elastic solids containing interacting multiple anisotropic inclusions subject to remote uniaxial tension. The method is applied to two-dimensional problems involving long parallel cylindrical inclusions. A detailed analysis of stress field at the interface between the matrix and the central inclusion is carried out for square and hexagonal packing of the inclusions. Effects of the number of anisotropic inclusions and various fiber volume fractions on the stress field at the interface between the matrix and the central inclusion are also investigated in detail. The accuracy of the method is validated by solving the single inclusion problem for which solutions are available in the literature.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 1999.04a
• /
• pp.93-99
• /
• 1999

조화진동하는 점진원에 의한 반무한 탄성체의 응답해석을 수행해 탄성체의 임의의 깊이에서의 응답을 나타내는 계산식을 유도했다 이결과는 최근 연구개발이 진행되고 있는 조화진원에 의한 정밀 지하구조탐사에 중요한 이론적 바탕이 된다. 먼저 실용상 중요한 수평가진에 의한 응답을 계산했다 표면에 큰 응답이 표면파의 형태로 발생하지만 수평진원의 에너지 방사형태는 지향성을 가지고 있어 진원아래의 원뿔형의 영역이 크게 여기된다는 사실을 밝혔다.