• Journal of the Korea Concrete Institute
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• v.23 no.4
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• pp.421-430
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• 2011

As a fundamental study to introduce the reliability-based design code, a statistical study is conducted for the material strength data collected from domestic construction sites. In order to develop a rational design code based on statistics and reliability theory, it is essential to obtain the statistical properties of material strength. Material strength data for concrete, reinforcing bars, and prestressing strands which are used in domestic construction sites are collected and statistically analyzed. Then, the statistical properties are compared with those used in the process of the reliability-based calibration of internationally leading design codes. The statistical properties of the domestic data are such that the bias factor is relatively uniform between 1.13 and 1.20 and the coefficient of variation is below 0.10. Reinforcing bar data show difference among different manufacturers but there is not much difference among re-bar diameters. In the case of tendons, which are high strength materials, both of the domestic and foreign data show smaller values of the bias factor and the coefficient of variation than those of concrete and re-bar. Statistical distribution of all the material strength can be properly assumed as normal, log-normal, or Gumbel distribution after analyzing the classified data by individual construction site and manufacturer rather than the mixed data obtained from different sources in order to express the individual distribution of each structure.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.1
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• pp.100-108
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• 2021

The purpose of this study is to analyze the reliability index of a design by applying the reduction factor of the recently developed fiber reinforced high strength concrete design guideline(draft). By collecting material and member test data performed for the development of the design guideline(draft), statistical characteristics of material strength and member strength analysis equations are obtained. A simul ation that appl ies the material statistical characteristics and the member anal ysis equation of the design guidel ine(draft) is performed, and the statistical characteristics of the section strength are calculated by combining the statistical characteristics of the analysis equation. Reliability analysis was performed by applying the load combination of the domestic highway bridge design code and concrete structural code, and it was confirmed that the design that applies the reduction factor for materials and members suggested in the design guideline(draft) satisfies the target reliability index.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.235-244
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• 2021

This study analyzes the applicability of limit state design method on bridge evaluation by considering the experiment of the existing bridge. The test strength of the member is obtained from the PSC beam bridge experiment. The test strength is compared with the calculated strength obtained from the statistical characteristics of material test strength and the two values are almost the same. The response modification factor and dynamic impact factor are obtained from the vehicle loading test. The rating factor is calculated by applying limit state design method as well as current evaluation method and the results are compared. The reliability index of the test bridge is calculated by using the statistical properties of the member strength obtained from material test and simulation. When the statistical properties of the PSC beam tested in this study are applied, the reliability index with a larger value was obtained than the reliability index obtained with the statistical properties of the design code.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.26-29
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• 2009

매크로 스케일(macro-scale)에서 구조재료의 거동을 보다 자세히 이해하기 위해서는 구조재료를 구성하고 있는 마이크로 스케일(micro-scale)에서의 미세구조에 대한 이해가 필요하다. 특히 다결정을 가진 다상재료는 상(phase) 분포 상태에 의해 그 특성이 다르기 때문에, 상 분포에 따른 재료의 특성을 이해하는 것이 중요하다. 본 연구에서는 미세구조의 상 분포 특성을 묘사할 수 있는 상관관계 함수를 이용하여 미세구조의 상 분포 상태를 나타내고, 이를 활용한 미세구조 재구성 방법을 사용하여 2상 미세구조에서 특정 미세구조와 유사한 상 분포를 가진 미세구조를 생성하고 그 특성을 비교하였다. 그리고 다양한 상 분포를 가진 미세구조들에 유한요소해석 기법을 적용하여 미세구조의 역학적인 거동을 분석하였다. 이를 통해, 제한된 정보를 이용하여 통계학적으로 유사한 특성을 나타내는 미세구조를 모델링 할 수 있음을 검증하였고, 이러한 미세구조들 간의 역학적 거동은 서로 거의 동일함을 확인하여 미세구조 재구성 기법이 재료의 역학적인 거동을 예측하는데 유용하게 사용될 수 있음을 확인하였다.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.59-62
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• 2000

In this study, the distribution of the effective modulus was investigated statistically Plain weave structures were modeled with random stacking phase shift angles and the effective modulus was calculated by the unit cell analysis. The analysis results indicated that the effect of random phase shift angles was significant on the modulus distribution. As the number of layers increased, the coefficient of variation decreased and higher degree of homogeneity was attained.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.2
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• pp.31-37
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• 2011

Understanding of the phase distribution in a multi-phase polycrystalline material is important because it can affect material properties and mechanical behaviors significantly. In this research, probability functions (two-point correlation and lineal-path functions) are used to represent the phase distributions of microstructures. The two-phase microstructures with random phase distribution are reconstructed using probability functions and compared with original samples. Mechanical behaviors of the virtual samples for different directions are evaluated using a finite element method. It is confirmed that microstructures with the same statistical characteristics can be generated using the reconstruction method. It is also demonstrated that the characteristics of the probability functions and mechanical reponses between the original and reconstructed microsturctures are statistically identical.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1184-1184
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• 2015

현재 XLPE 절연 케이블의 상시 운전 온도는 $90^{\circ}C$나 개발된 고내열성 절연재료의 상시운전온도는 $110^{\circ}C$로 향상되었다. 개발된 고내열성 절연재료는 XLPE 절연 케이블의 상시 운전온도($90^{\circ}C$)와 비상시운전온도($110^{\circ}C$), 고내열성 절연재료의 상시운전온도($110{\circ}C$), 비상시 운전온도($130{\circ}C$)을 바탕으로 하여 열 열화 온도와 기간이 설정되었다. 열 열화는 자연순환 건조기에서 설정된 온도와 기간 동안 수행되었고, 열 열화된 고내열성 절연재료는 Mckewon전극을 이용하여 AC파괴 시험이 진행 되었다. 파괴시험데이터는 와이블 분포함수를 이용하여 통계적으로 분석되었다.

• Magazine of the Korea Concrete Institute
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• v.3 no.4
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• pp.117-123
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• 1991

It is widely recognized that the strengths of reinforced concrete members have random characteristics due to the variability of the mechanical properties of concrete and steel, the dimensional error as well as incorrect placement of reinforcing bars. Statistical models of the variabilities of strengths of reinforced concrete members, therefore, need to be developed to evaluate the safety level implied in current practices. Based on the probabilistic models of basic factors affecting the R.C. member strengths, in this study, the probabilistic characteristics of member resistance have been studied through Monte Carlo simulation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.293-296
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• 2004

초고압 케이블의 절연물질로 널리 사용되고 있는 가교 폴리에틸렌의 전기적 특성은 라멜라 결정 조직의 밀도와 라멜라 조직의 성장방향과 밀접한 관련이 있는 것으로 알려지고 있다. 본 연구에서는 반도전 물질에 2종의 첨가제를 이용하여 처방한 3종의 반도전 컴파운드에 대하여 시편 제작 조건에 따른 미세 조직을 제어하여 폴리에틸렌의 미세 조직을 변화시킴으로써, 라멜라 조직이 전기적 특성에 미치는 영향을 분석하였다. 전기적 특성은 AC 절연파괴 전압을 측정하였으며, 미세 조직 변화를 조사하기 위하여 TEM 이미지 분석 통하여 라멜라 밀도를 통계적으로 정성 분석하여 상관관계를 규명하였다.

• Journal of Korean Society of Steel Construction
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• v.19 no.2
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• pp.139-146
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• 2007

The objective of the present study is to provide statistical resistance statistics for steel-concrete composite plate girder sections under positive and negative moments. Statistical properties on yield strength, tensile strength, elongation, and fracture toughness of domestic structural steel products, gathered from an analysis of over 16,000 samples, were evaluated. Using the steel samples for the plate girder, the bias factor and the coefficient of variation of the ultimate flexural resistance for representative composite plate girder sections under positive and negative flexures were presented. In calculating the ultimate flexural resistance of the composite section, the moment curvature relationships were developed using the incremental load approach considering material nonlinearity for the steel girder. The predicted statistics can be used in the future for the efficient calibration of LRFD code.