• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.3
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• pp.183-189
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• 2013

In this paper, uncertainties and failure criteria of structure are mathematically expressed by random variables and a limit state equation. A limit state equation is approximated by Fleishman's 3rd order polynomials and the theoretical moments of an approximated limit state equation are calculated. Fleishman introduced a 3rd order polynomial in terms of only standard normal distiribution random variables. But, in this paper, Fleishman's polynomial is extended to various random variables including beta, gamma, uniform distributions. Cumulants and a normalized limit state equation are used to calculate a theoretical moments of a limit state equation. A cumulative distribution function of a normalized limit state equation is approximated by a Pearson system.

• Magazine of the Korea Concrete Institute
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• v.6 no.5
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• pp.183-192
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• 1994

Seismic safety of RC structure can be evaluated by numerical analysis considering randomness of earthquake motion and hysteretic behavior of reinforced concrete, which is more rational than determirustic analysis. In the safety assessment of aseismatic structures by the deterministic theory, it is not easy to consider th effects of random variables but the reliability theory and random vibration theory are useful to assess seismic safety with considering random effects. This study aims at the evaluation of sesmic damage and risk of the RC frame structure by stochastic response analysis of hysteretic system and then the calculation stages of the prob ability of failure are presented.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.241-250
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• 1991

The reliability analysis for web frame of tanker is carried out by the probabilistic finite element method combined with the classical reliability method such as MVFOSM and AFOSM which can be used for calculating the probability of failure for the complicated structures in which the limit state equation is implicitly expressed. As random variables external load, elastic modulus, sectional moment of inertia and field stress are chosen and Parkinson's iteration algorithm in AFOSM is used for reliability analysis. By adding only the covariance data of the random variables to the input data set required for conventional finite element method, the present method can easily calculate the probability of failure at every element end as well as the covariances of structural reponses such as displacements at every element end and member forces at every element, even for the complicated ship structure.

• Computational Structural Engineering
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• v.7 no.3
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• pp.41-45
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• 1994

최적화 방법이 구조설계 분야에 사용된지 근30년이 지난 오늘 이론적 측면에서 보면 상당한 발전이 있어 왔다고 해도 과언이 아니다. 실무 입장에 볼 때 과연 얼마만큼 최적화 방법이 현실의 설계업무 속에 자리잡혀 있는가를 곰곰히 되새겨 볼 필요가 있다고 본다. 사실 실제와 이론 사이의 괴리를 줄여보려는 노력에서, 최적호 기술 분야에서도 기존의 확정론적 최적화 방법만이 아니라 확률론적 최적화방법에 대한 연구도 시작되었으리라 본다. 본문에서 언급한 Genetic Algorithm과 Evolutionary Strategy도 기존의 최적화 방법과 마찬가지 이유에서 복잡한 현실문제의 최적해를 추구하기 위한 또 하나의 방법으로 인식 될 필요가 있다고 보아 이 두 방법에 대한 개략적인 내용을 적었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1503-1506
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• 2007

수공구조물의 설계를 위해서 주로 사용되는 강우강도식은 연최대치 강우자료를 이용하여 빈도별 혹은 지속기간별 확률강우량을 구한 후 이 값들을 선형 혹은 비선형식의 형태로 회귀분석하여 구하게 된다. 그러나, 이와 같이 회귀분석을 이용하여 추정된 강우강도식은 원래의 강우자료가 가지고 있는 확률적인 특성을 재현한다고 하기는 어렵기 때문에, 본 연구에서는 연최대치 강우자료에 대한 적정 확률분포형으로부터 직접 강우 강도식을 유도하는 방법을 적용하여 대상지역 강우강도식의 매개변수를 산정하였다. 선정된 적정 확률분포형을 이용하여 강우강도식의 매개변수를 추정하는데 있어서, 평균제곱오차의 제곱근을 최소화하는 형태의 목적함수를 구성한 후 유전자알고리즘을 이용하여 적절한 매개변수를 산정하였다. 산정된 매개변수를 사용한 강우강도식으로 구한 결과값과 기존의 강우강도식에 의한 결과값 그리고 지점빈도해석에 의한 결과값을 비교하여 본 연구에서 산정된 강우강도식의 적용성을 평가해 보았다.

• Computational Structural Engineering
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• v.2 no.2
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• pp.93-99
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• 1989

Since 1960's, structural engineers have recognized that the inherent random nature of loadings and materials as well as the imperfect structural analysis may be important factors in the structural safety evaluation. Based on the successful developments of the reliability-based structural analysis and design, the design criteria of the standards are recently developed(or modified) in the light of the probabilistic concepts. To develop the probability - based criteria for the domestic buildings, the probabilistic characteristic of loadings acting on structures should be defined first. In this study, therefore, live load data on apartment buildings have been collected and analyzed in systematic manner, and their probabilistic characteristics have been studied. Based on the results, the lifetime extreme values are computed and compared with current design loads. More rational design loads are suggested, which are more consistent in the probabilistic concepts.

• Journal of Korean Society of Steel Construction
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• v.13 no.5
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• pp.567-575
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• 2001

In order to consider statistical properties of probability variables used in the structural analysis the conventional approach using the safety factor based on past experience usually estimated the safety of a structure Also the real structures could only be analyzed with the error in estimation of loads material characters and the dimensions of the members. But the errors should be considered systematically in the structural analysis Safety of structure could not precisely be appraised by the traditional structural design concept Recently new aproach based on the probability concept has been applied to the assessment of structural safety using the reliability concept Thus the computer program by the Probabilitstic FEM is developed by incorporating the probabilistic concept into the conventional FEM method. This paper estimated for the reliability of a plane stress structure by Advanced First-Order Second Moment method using von Mises, Tresca and Mohr-Coulomb failure criterions. Verification of the reliability index and failure probability of attained by the Monte Carlo Simulation method with the von Mises criterion were same as PFEM, but the Monte Carlo Simulation were very time-consuming. The variance of member thickness and load could influence the reliability and failure probability most sensitively among the design variables from the results of the parameter analysis. The proper failure criterion according to characteristic of materials must be used for safe design.

• Economic and Environmental Geology
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• v.33 no.4
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• pp.295-307
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• 2000

Probabilistic analysis is a powerful method to quantify variability and uncertainty common in engineering geology fields. In rock slope engineering, the uncertainty and variation may be in the form of scatter in orientations and geometries of discontinuities, and also test results. However, in the deterministic analysis, the factor of safety which is used to ensure stability of rock slopes, is based on the fixed representative values for each parameter without a consideration of the scattering in data. For comparison, in the probabilistic analysis, these discontinuity parameters are considered as random variables, and therefore, the reliability and probability theories are utilized to evaluate the possibility of slope failure. Therefore, in the probabilistic analysis, the factor of safety is considered as a random variable and replaced by the probability of failure to measure the level of slope stability. In this study, the stochastic properties of discontinuity parameters are evaluated and the stability of rock slope is analyzed based on the random properties of discontinuity parameters. Then, the results between the deterministic analysis and the probabilistic analysis are compared and the differences between the two analysis methods are explained.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.4
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• pp.111-118
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• 2010

Reinforced steel corrosion due to concrete carbonation is one of main factors on the durability of RC structure. The carbonation velocity have an effect on carbon dioxide density, concrete quality and structural shape. Specially, these problems have increased in urban area. This study investigates the carbonation status of the bridges and quantifies the effect of carbonation based on various domestic field data. The failure probability of durability is evaluated on the basis of reliability concept. According to experimental results of the carbonation depth, the carbonation depth increased with structural age and carbonation velocity decreased with high strength of concrete. In most cases, the failure probability of durability by carbonation was more than 10%. Also, The results requires the minimum cover thickness of 70-80mm for target safety index(${\beta}$=1.3) proposed by Korean concrete specification.

• Korean Journal of Construction Engineering and Management
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• v.8 no.5
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• pp.71-79
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• 2007

It is common that the analysis of VE/LCC is performed in design phase of quay wall structures. The analysis is mainly executed based on experience and engineering sense of expert considering the selection of construction method, construction and maintenance cost. Recently there are increasing demands on the analysis that includes uncertainty and vulnerability of input parameters, for this purpose, fuzzy reliability based probabilistic VE/LCC analysis model for quay wall structures is suggested. In VE/LCC analysis for quay wall structures, the application of probabilistic analysis method give very similar results compare with those of deterministic analysis method. It is anticipated that the methodology proposed in this paper can also be utilized in the design and maintenance phase of other facilities where decision making is made for the probabilistic life cycle cost and value analysis.