• Geomechanics and Engineering
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• v.21 no.3
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• pp.289-300
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• 2020

Estimating the damage induced by an explosion around a blast hole has always been a challenging issue in geotechnical engineering. It is difficult to determine an exact dimension for damage zone since many parameters are involved in the formation of failures, and there are some uncertainties lying in these parameters. Thus, the present study adopted a probabilistic approach towards this problem. First, a reliability model of the problem was established and the failure probability of induced damage was calculated. Then, the corresponding exceedance risk curve was developed indicating the relation between the failure probability and the cracked zone radius. The obtained risk curve indicated that the failure probability drops dramatically by increasing the cracked zone radius so that the probability of exceedance for any crack length greater than 4.5 m is less than 5%. Moreover, the effect of each parameter involved in the probability of failure, including blast hole radius, explosive density, detonation velocity, and tensile strength of the rock, was evaluated by using a sensitivity analysis. Finally, the impact of the decoupling ratio on the reduction of failures was investigated and the location of its maximum influence was demonstrated around the blast point.

• Journal of Korean Society for Quality Management
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• v.21 no.2
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• pp.121-130
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• 1993

In this paper, we relate the reliability of the system to the reliabilities of the components or subsystems. We discussed the basic concept of system reliability and present a method to determine probabilities of failure of coherent system components under various conditions, especially forcused on probability of component or subsystem failure before system failure. Several examples illustrate the procedure.

• Journal of the Korean Society of Safety
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• v.21 no.1 s.73
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• pp.28-34
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• 2006

A procedure of estimating failure probability is demonstrated for a pressurized pipe of CrMo steel used at $538^{\circ}C$. Probabilistic fracture mechanics were employed considering variations of pressure loading, material properties and geometry. Probability density functions of major material variables were determined by statistical analyses of implemented data obtained by previous experiments. Distributions of the major variables were reflected in Monte Carlo simulation and failure probability as a function of operating time was determined. The creep crack growth life assessed by conventional deterministic approach was shown to be conservative compared with those obtained by probabilistic one. Sensitivity analysis for each input variable was also conducted to understand the most influencing variables to the residual life analysis. Internal pressure, creep crack growth coefficient and creep coefficient were more sensitive to failure probability than other variables.

• Journal of Industrial Technology
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• v.3
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• pp.53-63
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• 1983

The probability of failure is used to analyze the reliability of three dimensional slope failure, instead of conventional factor of safety. The strength parameters are assumed to be normal variated and beta variated. These are interval estimated under the specified confidence level and maximum likelihood estimation. The pseudonormal and beta random variables are generated using the uniform probability transformation method according to central limit theorem and rejection method. By means of a Monte-Carlo Simulation, the probability of failure is defined as; Pf=M/N N : Total number of trials M : Total number of failures Some of the conclusions derived from the case study include; 1. Three dimensional factors of safety are generally much higher than 2-D factors of safety. However situations appear to exist where the 3-D factor of safety can be lower than the 2-D factor of safety. 2. The F3/F2 ratio appears to be quite sensitive to c and ${\phi}$ and to the shape of the 3-D shear surface and the slope but not to be to the unit weight of soil. 3. In cases that strength parameters are assumed to be normal variated and beta variated, the relationships between safety factor and the probability of failure are fairly consistent, regardless of the shape of the 3-D shear surface and the slope. 4. As the c-value is increased, the probability of failure for the same safety factor is increased and as the ${\phi}-value$ is increased, the probability of failure for the same safety factor is decreased.

• Journal of the Korean GEO-environmental Society
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• v.18 no.3
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• pp.31-38
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• 2017

The purpose of this study is to propose a chart that can easily estimate the seismic failure probability of small and medium sized earthfill dams with little geotechnical information. By considering the existing method and procedure for estimating the seismic failure probability of a dam, the zero seismic failure probability curve, on which the seismic probability is zero regardless of the geotechnical properties of the dam, was determined in the form of hyperbola in the dam height and freeboard ratio plane. It was confirmed that the dam height-freeboard ratio distribution pattern of the Korean small and medium sized dams was shaped like a hyperbola like the zero seismic failure probability curve. Therefore, a estimation chart was constructed in which a number of seismic failure probability contours are represented by a number of hyperbolas at regular intervals in the dam height-freeboard ratio plane. The proposed chart was applied to the calculation of the seismic failure probability of two small and midium sized dams with relatively well-managed geotechnical properties and the validity of the chart was confirmed by comparison with the results obtained by the existing procedures and methods. In the future, the proposed chart is expected to be useful in considering investment priorities for maintenance and reinforcement of small and medium sized dams in preparation for earthquakes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.685-692
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• 2004

A stochastic approach has been presented for superplastic deformation of Ti-6Al-4V alloy, and probability functions are used to model the heterogeneous phase distributions. The experimentally observed spatial correlation functions are developed, and microstructural evolutions together with superplastic deformation behavior have been investigated by means of the two-point and three-point probability functions. The results have shown that the probability varies approximately linearly with separation distance, and deformation enhanced probability changes during the process. The stress-strain behavior with the evolutions of probability function can be correctly predicted by the model. The finite element implementation using Monte Carlo simulation associated with reconstructed microstructures shows that better agreement with experimental data of failure strain on the test specimen.

• Earthquakes and Structures
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• v.14 no.5
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• pp.425-436
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• 2018

The design of seismically isolated structures considering the stochastic nature of excitations, base isolators' design parameters, and superstructure properties requires robust reliability analysis methods to calculate the failure probability of the entire system. Here, by applying artificial neural networks, we proposed a robust technique to accelerate the estimation of failure probability of equipped isolated structures. A three-story isolated building with susceptible facilities is considered as the analytical model to evaluate our technique. First, we employed a sensitivity analysis method to identify the critical sources of uncertainty. Next, we calculated the probability of failure for a particular set of random variables, performing Monte Carlo simulations based on the dynamic nonlinear time-history analysis. Finally, using a set of designed neural networks as a surrogate model for the structural analysis, we assessed once again the probability of the failure. Comparing the obtained results demonstrates that the surrogate model can attain precise estimations of the probability of failure. Moreover, our proposed approach significantly increases the computational efficiency corresponding to the dynamic time-history analysis of the structure.

• Journal of the Korean Society of Safety
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• v.22 no.4
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• pp.7-12
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• 2007

In order to evaluate the integrity of Zr-2.5Nb pressure tubes, probabilistic fracture mechanics(PFM) approach was employed. Failure assessment diagram(FAD), plastic collapses, and critical crack lengths(CCL) were used for evaluating the failure probability as failure criteria. The Kr-FAD as failure assessment diagram was used because fracture of pressure tubes occurred in brittle manner due to hydrogen embrittlement of material by deuterium fluence. The probabilistic integrity evaluation observed AECL procedures and used fracture toughness parameters of EPRI and recently announced theory. In conclusion, the probabilistic approach using the Kr-FAD made it possible to determine major failure criterion in the pressure tube integrity evaluation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.630-633
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• 2004

Generally, component and FR-4 board are connected by solder joint. Because material properties of components and FR-4 board are different, component and FR-4 board show different coefficients of thermal expansion (CTE) and thus strains in component and board are different when they are heated. That is, the differences in CTE of component and FR-4 board cause the dissimilarity in shear strain and BGA solder joint s failure. The first order Taylor series expansion of the limit state function incorporating with thermal fatigue models is used in order to estimate the failure probability of solder joints under heated condition. A model based on plastic-strain rate such as the Coffin-Manson Fatigue Model is utilized in this study. The effects of random variables such as frequency, maximum temperature, and temperature variations on the failure probability of the BGA solder joint are systematically investigated by using a failure probability model with the first order reliability method(FORM).

• 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.