• Structural Engineering and Mechanics
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• 제42권1호
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• pp.121-129
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• 2012

All contemporary seismic Codes have adopted smooth design acceleration response spectra, which have derived by statistical analysis of many elastic response spectra of natural accelerograms. The above smooth design spectra are characterized by two main branches, an horizontal branch that is 2.5 times higher than the peak ground acceleration, and a declining parabolic branch. According to Eurocode EN/1998, the period range of the horizontal, flat branch is extended from 0.1 s, for rock soils, up to 0.8 s for softer ones. However, from many natural recorded accelerograms of important earthquakes, the real spectral amplification factor appears to be much higher than 2.5 and this means that the spectrum leads to an unsafe seismic design of the structures. This point is an issue open to question and it is the object of the present study. In the present paper, the spectral amplification factor of the smooth design acceleration spectra is re-calculated on the grounds of a known "reliability index" for a desired probability of exceedance. As a pilot scheme, the seismic area of Greece is chosen, as it is the most seismically hazardous area in Europe. The accelerograms of the 82 most important earthquakes, which have occurred in Greece during the last 38 years, are used. The soil categories are taken into account according to EN/1998. The results that have been concluded from these data are compared with the results obtained from other strong earthquakes reported in the World literature.

• Geomechanics and Engineering
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• 제29권6호
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• pp.599-614
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• 2022

In this study, the reliability analysis of internal and external stabilities of Reinforced Soil Walls (RSWs) under static and seismic loads are investigated so that it can help the geotechnical engineers to perform the design more realistically. The effect of various variables such as angle of internal soil friction, soil specific gravity, tensile strength of the reinforcements, base friction, surcharge load and finally horizontal earthquake acceleration are examined assuming the variables uncertainties. Also, the correlation coefficient impact between variables, sensitivity analysis, mean change, coefficient of variation and type of probability distribution function were evaluated. In this research, external stability (sliding, overturning and bearing capacity) and internal stability (tensile rupture and pull out) in both static and seismic conditions were investigated. Results of this study indicated sliding as the predominant failure mode in the external stability and reinforcing rupture in the internal stability. First-Order Reliability Method (FORM) are applied to estimate the reliability index (or failure probability) and results are validated using the Monte Carlo Simulation (MCS) method. The results showed among all variables, the internal friction angle and horizontal earthquake acceleration have dominant impact on the both reinforced soil wall internal and external stabilities limit states. Also, the type of probability distribution function affects the reliability index significantly and coefficient of variation of internal friction angle has the greatest influence in the static and seismic limits states compared to the other variables.

• 한국전자파학회논문지
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• 제11권3호
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• pp.352-357
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• 2000

이 논문에서는 동기 MPSK 신호에 대하여 새로운 간단한 심볼 오류 확률 하한식을 유도하고 분석한다. 보통 심볼 오류 확률 유도는 먼저 덧셉꼴 백색 정규잡음(AWGN) 환경에서 유도하고 이에 대한 결과를 바탕으로 여러 페이딩 환경에서의 심볼 오류 확률을 구하는 것이 일반적인 방법이다. 그러나 동기 MPSK의 경우는 여러 페 이딩 환경에서의 오류 확률 식이 구해져 있으나 가장 기본이 되는 덧셈팔 백색 정규 잡음 환경에서는 정확히 closed-form으로 유도하지 못하는 것으로 알려져 있다. 여기서는 먼저 나카가미 페이딩 환경에서 동기 MPSK 신호의 심볼 오류 확률식을 이용하여 나카가미 페이딩 지수가 무한대로 감에 따라 페이딩이 없는 덧셈꼴 백색 정규 잡음 채널로 돌아가는 성질을 이용하여 새로운 근사식을 유도하고 분석한다.

• 한국해안·해양공학회논문집
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• 제21권5호
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• pp.405-409
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• 2009

중요도추출법을 이용한 항만구조물의 신뢰성해석방법을 제시하였다. 몬테카를로모사법(Monte Carlo Simulation)을 이용하여 신뢰성해석을 수행할 때 전도파괴확률과 같이 매우 낮은 파괴확률을 가진 경우는 해석시간이 과다하게 소요되는 문제점이 있다. 항만구조물 신뢰성해석 시 나타나는 이러한 문제를 극복하기 위해 파괴면주위의 추출점을 이용하여 해석시간을 단축시킬 수 있는 중요도추출법을 적용하였다. 중요도추출법을 항만구조물에 적용한 경우 파괴확률이 매우 낮은 파괴모드에 대한 신뢰성해석을 효율적으로 수행할 수 있음을 보였다. 수치해석에서 케이슨 안벽의 신뢰성해석을 수행하였으며 파괴확률의 낮고 높음에 따른 중요도추출법의 효용성을 검증하였다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회 논문집
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• pp.867-872
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• 2005

This study introduces a method to evaluate the probability of a specific area to be affected by a drought of a given severity and shows its potential for investigating agricultural drought characteristics. The method is applied to Gyeonggi as a case study. The proposed procedure includes Standard Precipitation Index(SPI) time series, which are linearly transformed by the Empirical Orthogonal Functions(EOF) method, These EOFs are extended temporally with AutoRegressive Moving Average(ARMA) method and spatially with Kriging method. By performing these simulations, long time series of SPI can be simulated for each designed grid cell in whole Gyeonggi area. The probability distribution functions of the area covered by a drought and the drought severity are then derived and combined to produce drought severity-area-frequency(SAF) curves.

• 한국항해학회지
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• 제11권1호
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• pp.67-91
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• 1987

In this paper, a synthetic method for evaluating the seakeeping performance of a ship in waves is studied. For the prediction and evaluation of irregular phenomena to be correlated each other, the multi-dimensional Rayleigh's joint probability density function and the cumulative distribution function are approximated. According to this approximated function, it is able to calculate easily the occurrence probability of the factors on seakeeping performance. We proposed an evaluation method and an index to be defined by the seakeeping performance reliability, that is considered as the dangerousness and the relative dangerousness of the factors on seakeeping performance in waves. The use of this method aid index will be effective to install the sensors which are necessary to evaluate the states of ships at sea. Some example of the calculations by this method for 175m length single screw container ship equipped with diesel engine are also presented.

• 한국GIS학회:학술대회논문집
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• 한국GIS학회 2003년도 공동 춘계학술대회 논문집
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• pp.71-76
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• 2003

The purpose of this study is the development, application and assessment of probability and artificial neural network methods for assessing landslide susceptibility in a chosen study area. As the basic analysis tool, a Geographic Information System (GIS) was used for spatial data management. A probability method was used for calculating the rating of the relative importance of each factor class to landslide occurrence, For calculating the weight of the relative importance of each factor to landslide occurrence, an artificial neural network method was developed. Using these methods, the landslide susceptibility index was calculated using the rating and weight, and a landslide susceptibility map was produced using the index. The results of the landslide susceptibility analysis, with and without weights, were confirmed from comparison with the landslide location data. The comparison result with weighting was better than the results without weighting. The calculated weight and rating can be used to landslide susceptibility mapping.

• 한국안전학회지
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• 제24권2호
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• pp.62-68
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• 2009

Life Cycle Cost(LCC) is adopted to decide the target of safety level in designing suspension bridges. The LCC are evaluated considering two types of uncertainty; aleatory and epistemic. The nine alternative designs of suspension bridge are simulated to decide the safety level which can minimize the LCC. The LCC is calculated through the probability of failure and safety index including the uncertainty. This method results in the useful tool deciding the optimum safety level with minimal LCC as the main design factor.

• Journal of the Korean Statistical Society
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• 제27권3호
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• pp.289-303
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• 1998

For square contingency tables with ordered categories, Tomizawa (1995) considered two kinds of measures to represent the degree of departure from global symmetry, which means that the probability that an observation will fall in one of cells in the upper-right triangle of square table is equal to the probability that the observation falls in one of cells in the lower-left triangle of it. This paper proposes a generalization of those measures. The proposed measure is expressed by using Cressie and Read's (1984) power divergence or Patil and Taillie's (1982) diversity index. Special cases of the proposed measure include TomiBawa's measures. The proposed measure would be useful for comparing the degree of departure from global symmetry in several tables.

• 경영과학
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• 제24권2호
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• pp.115-126
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• 2007

Weekly minima of daily log returns of Korean composite stock price index 200 and its five industry-based business divisions over the period from January 1990 to December 2005 are fitted using two block-based extreme distributions: Generalized Extreme Value(GEV) and Generalized Logistic(GLO). Parameters are estimated using the probability weighted moments. Applicability of two distributions is investigated using the Monte Carlo simulation based empirical p-values of Anderson Darling test. Our empirical results indicate that both the GLO and GEV models seem to be comparably applicable to the weekly minima. These findings are against the evidences in Gettinby et al.[7], who claimed that the GEV model was not valid in many cases, and supported the significant superiority of the GLO model.