• Explosives and Blasting
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• v.37 no.3
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• pp.25-33
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• 2019

Controlling the blast-induced damage zone(BDZ) in mining excavation is a significant issue for the safety of employees and the maintenance of facilities. Numerous studies have been conducted to accurately predict the BDZ in underground mining. This study employed the dynamic fracture process analysis (DFPA) to estimate the BDZ from a single hole blasting. The estimated BDZ were compared with the results obtained by Swedish empirical equation. The DFPA was also used to investigate the control mechanism of BDZ and fracture plane formation around perimeter holes for underground mining blasting.

• Computational Structural Engineering
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• v.9 no.1
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• pp.65-76
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• 1996

The initiation and growth of microcracks or microvoids inside concrete results in the progressive degradation of concrete. This damage processing along processing along with plastic deformation is main cause of nonlinear behavior of concrete. In this study, a continuum damage model of concrete is developed for the analysis of the nonlinear behavior of concrete due to damage and elasto-plastic deformation. Anisotropic damage tensor is used to describe the anisotropy of concrete and hypothesis of equivalent elastic energy is used to define the effective elastic tensor. The damage model including the damage evolution law and constitutive equation is derived with damage variable and damage surface which is defined by damage energy release rate by using the Helmholtz free energy and dissipation potential based on the thermodynamic principles. By adopting a typical plasticity model of concrete, plasticity of concrete is included to this model. Afinite element analysis program implemented with this model was developed and finite element analysis was performed for the analyses of concrete subjected to uniaxial and biaxial loadings. Comparison of the results of analysis with those of experiments and other models shows that the model successfully predicts the nonlinear behavior of concrete.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.215-218
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• 2001

태핑 검사법을 이용한 복합재료 구조물의 손상검사 과정을 수치해석을 이용하여 모사하였다. 타격체에 의한 태핑을 모사하기 위해 동적접촉 알고리듬을 이용한 유한요소법을 이용하였다. 손상의 유무를 판별하는데 사용되는 척도로서 타격체와 구조물의 접촉하중의 시간이력을 계산하였다. 손상이 없는 복합재료 평판과 층간 분리 손상이 있는 복합재료 평판에 대한 해석을 통하여 접촉특성의 변화를 고찰하였다. 또한 태핑 검사법의 민감도에 대한 해석도 수행하였다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.1
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• pp.81-88
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• 1998

과적차량의 통행에 의한 교량구조물의 손상도를 평가하는 방법의 개발이 매우 활발하다. 본 연구에서는 과거 15년동안 통행한 교통데이타를 분석하고, 이 데이타를 근거로 교량의 손상도를 분석한다. 차량의 분류는 4종으로 대표하여 차량하중을 분석하였으며 해석시에는 이를 대표하는 2종을 사용하였다. 3차원해석을 통하여 구한 영향면을 이용하여 부재력을 계산하고 이를 이용하여 등가응력범위를 구한다. 이 결과는 모형실험을 통하여 구한 피로결과와 비교하였다. 분석결과 설계하중을 초과하는 과적차량이 교량에 미치는 손상정도는 적은 통행빈도에도 불구하고 매우 큼을 알 수 있고, 이러한 실제교통량의 분석을 통한 교량의 손상평가방법은 과적차량에 의한 교량손상정도를 유용하게 평가할 수 있다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.6
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• pp.359-366
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• 2020

In this study, a simulation-based damage estimation method for helidecks is proposed using an artificial neural network. The structural members that share a connecting node in the helideck are regarded as a damage group, and a total of 37,400 damage scenarios are numerically generated by applying randomly assigned damage to up to three damage groups. Modal analysis is then performed for all the damage scenarios, which are selectively used as either training or validation or verification sets based on the purpose of use. An artificial neural network with three hidden layers is constructed using a PyTorch program to recognize the patterns of the modal responses of the helideck model under both damaged and undamaged states, and the network is successively trained to minimize the loss function. Finally, the estimated damage rate from the proposed artificial neural network is compared to the actual assigned damage rate using 400 verification scenarios to show that the neural network is able to estimate the location and amount of structural damage precisely.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.43-46
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• 2009

열탄성 부영역, 열탄점소성/손상 부영역, 공유면, 접촉 공유면에 기반을 둔 영역/경계 분할법을 적용하여 재료 비선형성을 갖는 열탄점소성 손상 문제와 경계 비선형성을 갖는 접촉 문제의 효율적인 해석을 제안하였다. 영역 및 경계 분할에 관련된 공유면 및 접촉 공유면에서의 연속 구속 조건을 처리하기 위하여 간단한 벌칙 함수 기법을 적용하였다. 결과적으로 재료 및 경계 비선형성은 소수의 부영역과 접촉 경계면에서 계산되는 유한요소 행렬들에 국한된다. 따라서 적절한 해석 알고리듬을 구성하면 대폭적인 효율성 향상이 가능하게 된다. 대변형과 같은 기하학적 비선형성은 고려하지 않았으며, 간단한 수치 실험을 통해서 열탄점소성 손상 및 접촉 해석의 효율성에 관련된 기본적인 특성을 분석하였다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.4
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• pp.135-144
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• 2006

In performing a risk analysis of structures under earthquakes, it is imperative to identify the vulnerability of structures associated with various damage stages considering structural properties, soil-structure interactions, site condition, and so on. In this paper, the method to derive a representative fragility curve of seismic isolated LRB(lead rubber bearing) bridges is proposed. In which, the curve is assumed log-normally distribution with two parameters. The risk analysis of seismic isolated LRB bridges considering earthquake effects such as PGA, PGV, SA, SV, and SI is also performed to assure the earthquake resisting capability of the structures. An practical way for constructing the representative fragility curves is also recommended combining fragility curves of structures.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.4
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• pp.306-313
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• 2011

The damage tolerance analysis is required to guarantee the structural safety and the reliability for aircraft components. The damage tolerance method, which evaluate the life considering the initial crack, considers a fatigue design model of the aircraft main structure. The fatigue crack growth life should be calculated in damage tolerance analysis and the inspection time to define the replacement cycle. In this paper, the damage tolerance analysis is performed for a turbine wheel which has complex geometry. The equation of the stress intensity factor for complex geometry is hard to know, so that they are usually processed by finite element analysis which takes long time. To solve this problem, the stress intensity factors at specified crack are obtained by the FEA and the crack growth life is evaluated using the surrogate model which is generated by the regression analysis of the FEA data. From the results, the efficiency of the crack growth life calculation and the damage tolerance analysis could be increased by taking the surrogate model.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.2
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• pp.41-50
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• 2003

In this paper, nonlinear parallel structural analyses are introduced by using the parallel multifrontal solver and damage localization for 2D and 3D crack models is presented as the application of nonlinear parallel computation. The parallel algorithms related with nonliear reduce the amount of memory used is carried out because many variables should be utilized for this highly nonlinear damage analysis. Also, Riks' continuation method is parallelized to search the solution when strain softening occurs due to damage evolution. For damage localization problem, several computational models having up to around 1-million degree of freedoms are used. The parallel performance in this nonlinear parallel algorithm is shown through these examples and the local variation of damage at crack tip is compared among the models with different degree of freedoms.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.2
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• pp.257-270
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• 2000

The objective of this study is to develop a damage model based on damage mechanics that can be used to analyze the mechanical behavior of structures with defects and the global behavior of damaged structures. A modified second order damage tensor that can be applied to finite element analysis is used to reflect the effect of damage. The damage stress computed from the effective stress is considered as an additional loading term acting on nodes and can represent the effect of crack surface. The accuracy of the proposed algorithm is verified by comparing the analysis results with the experimental data from other studies and the analysis results based on transverse isotropic theory. The developed damage model is applied to the analyses of structures with cracks under linear elastic condition. The comparisons confirmed that the quantitative analysis of the structural behavior due to crack orientation and multiple sets of cracks is possible. Also, the damage caused by rock excavation and fault zone is analyzed. The results also showed that the developed model can effectively analyze the global behavior of damaged structures.