• Journal of Korean Tunnelling and Underground Space Association
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• v.3 no.4
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• pp.3-15
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• 2001

Generally, it has been noted that underground structures have a consistent record of suffering much less damage than surface facilities during earthquakes; but it is still necessary to illustrate the dynamic response of tunnel structures subject to earthquake loadings and to provide the appropriate method for the seismic analysis of underground tunnel structures since many types of underground structures have been and will be constructed in countries situated within seismic zones. In this study, first, seismic analyses for underground tunnel structures are performed by using quasistatic analysis method and dynamic analysis method. Second, seismic analyses in tunnel portals are performed by using above methods. The results of seismic analyses for the tunnel structure show that the tunnel structure conforms to ground deformation and that seismic design by using the quasi-static analysis method is more conservative than that by using the dynamic analysis. The results of the dynamic FEM analysis for the tunnel structure show that the simplified 2-D FEM analysis using a sine wave rather than the 3-D FEM analysis can be adopted for seismic analysis. Finally, the results of the dynamic FEM analysis in tunnel portals show that the force acting on the lining is largest near to the tunnel portal when an earthquake wave propagates parallel to tunnel axis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.3
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• pp.129-138
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• 1993

In this study, the applicability of finite analytic method (FAM) is studied by selecting linearized-Burgers equation and Burgers equation which have convective and diffusive behaviors as the model equation of Navier-Stokes equations and by comparing numerical solution of finite difference method (FDM) and finite analytic method. The results are as follows. It is shown that the convergence of FAM for steady-state analytic solution of linearized-Burgers equation and Burgers equation is better than that of FDM under the same criteria. Also the accuracy of FAM for transient solution of Burgers equation is excellent. Especially, it is shown that oscillation phenomenon due to dispersion errors which occur according to the choice of grid size in FDM does not occur in FAM at all. So, it can be thought that FAM is numerically very stable scheme, which is free from dispersion errors.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.703-713
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• 2002

Recently, an improved EFG(Element-Free Galerkin) crack analysis technique, which includes a discontinuous approximation and a singular basis function on the auxiliary supports, was developed. The technique is able to accurately analyze the crack propagation problem without any modification of the analysis model; however, it shows some dependency on the analysis parameters used. In this study, the effect of analysis parameters such as the size of compact support, dilation parameter, the smoothness of shape function around the crack tip, and the number of node using auxiliary supports on the accuracy of solution has been investigated. Through a patch test with a crack, relative L₂ error norm of stresses and the stress intensity factor were computed and compared for various analysis parameters and the results were presented as guidelines for adequate choice of analysis parameters.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.4
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• pp.38-47
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• 2020

A parametric study for analytical correction using measurement results was performed to minimize errors in the predictions of column shortening in RC tall building. The parameters of the column shortening analytical correction are the execution standard of analytical correction, the value of the analytical correction, and the measurement location, and the analytical correction models with the parameters were applied to the construction sequence analysis of a 41-story RC building to compare and analyze the correction effect according to the parameter. The reduction ratio of the error value for each floor was compared with the number of corrections and the total corrected value, and it was confirmed that the error tended to be minimized when the execution standard of analytical correction was performed based on a regular interval, when the analysis correction value was corrected by the error value, and when the measurement position was measured every floor. From this, it was confirmed that the most appropriate analytical correction model can be derived by applying multiple analytical correction models to the actual analysis model.

• Journal of the Korean Geosynthetics Society
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• v.19 no.1
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• pp.35-44
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• 2020

Design techniques for the deep mixing method, one of the soft ground improvement methods, include two ways to interpret the ground as composite ground and pile ground. However, since comparative studies on these two approaches are insufficient, it is difficult to clearly define the analysis criteria in the design. In this study, two-dimensional and three-dimensional analyses have been performed with different conditions. The three conditions, the embankment height, depth of soft ground, and replacement ratio of reinforcement zones were varied and the analysis was performed on the basis of the assumption of composite ground and pile ground for each condition. As a result, the minimum depth of improvement in the two-dimensional analysis was deeper by 6.85~9.08% than in the three-dimensional analysis. The pile ground analysis showed that the depth of improvement was deeper by 12.22~14.45% than the composite ground analysis. Based on these results, it is concluded that for more accurate design, three-dimensional analysis should be performed rather than two-dimensional analysis. also, it is judged that necessary to analyze the ground as composite ground for economical design, and as the pile ground analysis for stable design.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.3
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• pp.624-631
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• 2011

In this paper, the RCF method is used in sensitivity analysis problems of the discrete power systems including both series FACTS equipments such as TCSC in transmission lines and generator controllers such as Exciter and PSS in generator terminal. To apply the RCF method in small signal stability problems of discrete power systems, state transition equations of controllers and TCSC are derived and the sensitivity calculation algorithm using state transition equations in discrete time domain is devised. The results of eigenvalue analysis showed that the variations of eigenvalues after periodic switching operations of TCSC can be calculated exactly by the RCF method and the change of firing angles in TCSC have important effect to determine the stability of power systems.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.340-340
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• 2018

전 세계적으로 기후변화로 인해 나타나는 이상기후의 영향을 고려하기 위해서 수문빈도해석분야에서는 비정상성 빈도해석에 관한 연구가 활발히 진행 중이다. 자료의 비정상성을 고려하여 빈도해석을 수행하는 방법은 다양하게 연구되어오고 있는데, 그중 시간에 따른 자료의 변화를 고려할 수 있도록 기존 모형의 매개변수에 시간을 고려할 수 있는 변수를 더하여 모형을 구축하는 기법이 비정상성 빈도해석기법으로 널리 활용되고 있다. 한편, 이러한 비정상성 가정에 관련한 연구들은 주로 지점빈도해석 기법을 중심으로 개발되어왔을 뿐, 아직 지역빈도해석기법을 대상으로 시도된 비정상성 연구는 미비한 실정이다. 지역빈도해석은 수문학적 동질지역이라는 가정을 바탕으로 표본의 확장을 통해 지점빈도해석보다 비교적 안정적인 빈도해석을 수행할 수 있는 기법으로 널리 알려져 있다. 따라서 지역빈도해석에서 수문학적 동질지역의 구분은 지역빈도해석 절차 중 가장 중요한 절차라고 할 수 있다. 이러한 수문학적 동질지역 구분을 위해서는 지점별로 가지고 있는 위치 정보나 수문 자료의 통계값과 같은 해당 지점을 대표할 수 있는 인자들이 필요하다. 본 연구에서는 모의실험을 통해 경향성이 나타나는 가상의 지점 자료를 생성한 뒤, 지역구분을 통해 자료의 비정상성이 나타나는 지역의 지역구분 결과를 살펴보고 이질성 척도(heterogenity measure)를 산정하였다. 이를 바탕으로 비정상성 지역빈도해석에서 이질성 척도의 적용성을 검토하고자 한다. 본 연구의 결과는 추후 기후변화의 영향이 나타나는 수문학적 동질 및 비 동질지역의 분석 및 비정상성 지역빈도해석을 위한 기초자료로 활용될 것으로 기대된다.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.3
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• pp.111-116
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• 2011

Analytical solutions for laterally loaded piles were derived. Critical pile length which can be considered as the length for behaving as long pile was investigated varying with densities of sandy soils. Lateral behaviors obtained from analytical solution and numerical solution were also investigated. Non-dimensional critical pile lengths obtained from analytical solutions for three types of pile head boundary conditions were 2.3~3.2. By comparing analytical solutions with numerical solutions, distribution of pile deflection and that of moment were similar and it can be seen that pile head deflection obtained by analytical method is conservative. And the values of moments were not too different between analytical solution and numerical solution.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.1
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• pp.201-209
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• 2021

In order to evaluate the vibrational characteristics of huge finite element models such as ships and offshore structures, it is essential to perform eigenvalue analysis and frequency response analysis. However, these analyzes necessitate excessive equipment and computation time, which require the development of a high-performance analysis program. In particular, a considerable computational analysis time is required when calculating the inverse matrix in a linear system of equations and analyzing the eigenvalue analysis. Therefore, it can be improved by applying the latest high-performance library. In this paper, the vibration analysis program that enables fast and accurate analysis was developed by applying 'PARDISO', a parallel linear system of equation calculation library, and 'ARPACK', a high-performance eigenvalue analysis library. To verify the accuracy and efficiency of proposed method, we compare ABAQUS with proposed program using numerical examples of marine engineering.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.206-208
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• 2006

본 논문은 전력기기에서 문제가 되는 온도상승에 대응하여 제품 개발시 선행 해석을 통한 온도 안정성 확보와 제품 신뢰성 향상, 설계 기간 단축을 위한 방안에 대하여 서술하고 있다. 전력기기의 온도 상승을 예측하기 위한 방법으로 전자계 해석과 열유동 해석을 동시에 수행하는 연계 해석법을 제안하며, 이 해석법의 검증을 위해 기중 차단기의 통전시 온도 상승에 대한 해석을 수행하였고, 실험을 통해 이름 검증하였다.