• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.311-314
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• 2003

Concrete structures such as bridge, pavement, airfield, and offshore structure are normally subjected to repeated load. This paper proposes a failure probability models of concrete subjected to split tension repeated-loads, based on experimental results. The fatigue tests were performed at the stress ratio of 0.1, the loading shape of sine, the frequency of 20Hz, and the stress levels of 90, 80 and 70%. The fatigue test specimen was 150mm in diameter and 75mm in thickness. The fatigue analysis did not include which exceeded 0.9 of statistical coefficient of determination values or did not failure at 2$\times$$10^6$ cycles. The graphical method, the moment method, and maximum likelihood estimation method were used to obtain Weibull distribution parameters. The goodness-of-fit test by Kolmogorov-Smirnov test was acceptable 5% level of significance. As a result, the proposed failure probability model based on the two-parameter($\alpha and \mu$) Weibull distribution was good enough to estimate accurately the fatigue life subjected to tension mode.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.469-474
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• 2008

The reason for crashworthy landing gear is to contribute to the overall aircraft design goals in the event of a crash. One of crashworthy landing gear design approaches is inclusion of structural fuse. Structural fuse is used to control the mode of failure of landing gear. If structural fuse doesn't work at desired condition, other unexpected accidents can occur. In this paper, failure probability is calculated for landing gear structural fuse and improvement measure is introduced to improve failure probability of structural fuse.

• Journal of the Korean Society for Railway
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• v.14 no.1
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• pp.24-30
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• 2011

Conventional slope stability analysis is focused on calculating minimum factor of safety or maximum probability of failure. To minimize inherent uncertainty of soil properties and analytical model and to reflect various analytical models and its failure shape in slope stability analysis, slope stability analysis method considering simultaneous failure probability for multi failure mode was proposed. Linear programming recently introduced in system reliability analysis was used for calculation of simultaneous failure probability. System reliability analysis for various analytical models could be executed by this method. For application analysis for embankment, the results of this method shows that system stability of embankment calculate quantitatively.

• Tunnel and Underground Space
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• v.31 no.5
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• pp.360-373
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• 2021

Many sources of uncertainty exist in geotechnical analysis ranging from the material parameters to the sampling and testing techniques. The conventional deterministic stability analysis of a plane failure in rock slope produce a safety factor but not a probability of failure or reliability index. In the conventional slope stability analysis by evaluating the ground uncertainty as an overall safety factor, it is difficult to evaluate the stability of the realistic rock slope in detail. This paper reviews some established probabilistic analysis techniques, such as the MCS, FOSM, PEM, Taylor Series as applied to plane failure of rock slopes in detail. While the Monte - Carlo methods leads to the most accurate calculation of the probability of safety, this method is too time consuming. Therefore, the simplified probability methods could be alternatives to the MCS. In this study, using these simple probability methods, the failure probability estimation of a plane failure in rock slope is presented.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.300-307
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• 2002

Bridge foundation failure considering the effect of local scour around pier foundations under hi-directional seismic excitations is examined in probabilistic perspectives. The seismic responses of bridges with deep foundations are evaluated with a simplified mechanical model, which can consider the local scour effect around the deep foundation in addition to many other components. The probabilistic characteristics of local scour depths are estimated by using the Monte Carlo simulation. The probabilistic characteristics of basic random variables used in the Monte Carlo simulation are determined from the actual hydraulic data collected in middle size streams in Korea. The failure condition of deep foundation is assumed as bearing capacity failure of the ground below the foundation base. The probability of foundation failure of a simply supported bridge with various scour conditions and hi-directional seismic excitations are examined. It is found that the local scour and the recovery duration are critical factors in evaluating the probability of foundation failure. Moreover, the probability of foundation failure under hi-directional seismic excitations is much higher than under uni-directional seismic excitations. Therefore, it is reasonable to consider hi-directional seismic excitations in evaluating the seismic safety of bridge systems scoured by a flood.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.10
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• pp.480-486
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• 2005

This paper proposes a method to consider an aging failure probability and survival probability of power system components, though only aging failure probability has been considered in existing mean life calculation. The estimates of the mean and its standard deviation is calculated by using Weibull distribution, and each estimated parameters is obtained from Data Analytic Method (Type H Censoring). The parameter estimation using Data Analytic Method is simpler and faster than the traditional calculation method using gradient descent algorithm. This paper shows calculation procedure of the mean life and its standard deviation by the proposed method and illustrates that the estimated results are close enough to real historical data of combustion turbine generating units in Korean systems. Also, this paper shows the calculation procedures of a probabilistic failure prediction through a stochastic data analysis. Consequently, the proposed methods would be likely to permit that the new deregulated environment forces utilities to reduce overall costs while maintaining an are-related reliability index.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.3
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• pp.147-155
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• 2023

This study aims to present a method to evaluate the relative risk of failure due to liquefaction of domestic small to medium-sized earthfill dams with a height of less than 15 m, which has little information on geotechnical properties. Based on the results of previous researches, a series of methods and procedures for estimating the probability of dam failure due to liquefaction, which calculates the probability of liquefaction occurrence of the dam body, the amount of settlement at the dam crest according to the estimation of the residual strength of the dam after liquefaction, the overtopping depth determined from the amount of settlement at the dam crest, and the probability of failure of the dam due to overtopping was explicitly presented. To this end, representative properties essential for estimating the probability of failure due to the liquefaction of small to medium-sized earthfill dams were presented. Since it is almost impossible to directly determine these representative properties for each of the target dams because it is almost impossible to obtain geotechnical property information, they were estimated and determined from the results of field and laboratory tests conducted on existing small to medium-sized earthfill dams in previous researches. The method and procedure presented in this study were applied to 12 earthfill dams on a trial basis, and the liquefaction failure probability was calculated. The analysis of the calculation results confirmed that the representative properties were reasonable and that the overall evaluation procedure and method were effective.

• Journal of the Korean Society of Safety
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• v.35 no.5
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• pp.30-38
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• 2020

In order to construct a dam, the diversion facility such as cofferdam and a diversion tunnel should be installed in advance. And size of a cofferdam depends on type of a main dam. According to the Korea Dam Design Standard, if the main dam is a concrete dam, design flood of the cofferdam is 1~2 years flood frequency. This means that overflow of the cofferdam occurs one time for 1 or 2 years, therefore, stability of the cofferdam should be secured against any overflow problem. In this study, failure probability analysis for the concrete cofferdam is performed considering the overflow. First of all, limit state function of the concrete cofferdam is defined for overturning, sliding and base pressure, and upstream water levels are set as El. 501 m, El. 503 m, El. 505 m, El. 507 m. Also, after literature investigation research, probabilistic characteristics of various random variables are determined, the failure probability of the concrete cofferdam is calculated using the Monte Carlo Simulation. As a result of the analysis, when the upstream water level rises, it means overflow, the failure probability increases rapidly. In particular, the failure probability is largest in case of flood loading condition. It is considered that the high upstream water level causes increase of the upstream water pressure and the uplift pressure on the foundation. In addition, among the overturning, the sliding and the base pressure, the overturing is the major cause for the cofferdam failure considering the overflow.

• Geomechanics and Engineering
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• v.36 no.6
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• pp.631-640
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• 2024

In the traditional slope stability analysis, ignoring the spatial variability of slope soil will lead to inaccurate analysis. In this paper, the K-L series expansion method is adopted to simulate random field of soil strength parameters. Based on Random Limit Equilibrium Method (RLEM), the influence of variation coefficient and fluctuation range on reliability of soil slope supported by micro-pile is investigated. The results show that the fluctuation ranges and the variation coefficients significantly influence the failure probability of soil slope supported by micro-pile. With the increase of fluctuation range of soil strength parameters, the mean safety factor of the slope increases slightly. The failure probability of the soil slope increases with the increase of fluctuation range when the mean safety factor of the slope is greater than 1. The failure probability of the slope increases by nearly 8.5% when the fluctuation range is increased from δ_v=2 m to δ_v =8 m. With the increase of the variation coefficient of soil strength parameters, the mean safety factor of the slope decreases slightly, and the probability of failure of soil slope increases accordingly. The failure probability of the slope increases by nearly 31% when the variation coefficient increases from COV_c=0.2, COV_φ=0.05 to COV_c=0.5, COV_φ=0.2.

• Geomechanics and Engineering
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• v.38 no.1
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• pp.93-106
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• 2024

The present paper investigates the spatial variability effect of soil property on the three-dimensional probabilistic characteristics of the bearing capacity factor (i.e., mean and coefficient of variation) of a circular footing resting on clayey soil where both mean and standard deviation of undrained shear strength increases with depth, keeping the coefficient of variation constant. The mean trend of undrained shear strength is defined by introducing the dimensionless strength gradient parameter. The finite difference method along with the random field and Monte Carlo simulation technique, is used to execute the numerical analyses. The lognormal distribution is chosen to generate random fields of the undrained shear strength. In the study, the potential failure of the structure is represented through the failure probability. The influences of different vertical scales of fluctuation, dimensionless strength gradient parameters, and coefficient of variation of undrained shear strength on the probabilistic characteristics of the bearing capacity factor and failure probability of the footing, along with the probability and cumulative density functions, are explored in this study. The variations of failure probability for different factors of safety corresponding to different parameters are also illustrated. The results are presented in non-dimensional form as they might be helpful to the practicing engineers dealing with this type of problem.