• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.2
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• pp.154-162
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• 2011

A reliability analysis model is developed for evaluating the crest freeboard of vertical breakwaters based on the concepts of maximum overtopping volume of individual wave. A reliability function is formulated by defining the margin of admissible overtopping volume and maximum overtopping volume that is depend on the number of overtopping waves, dimensionless crest freeboard, and mean overtopping discharge. In addition, Level III MCS technique is straightforwardly suggested by which the related empirical parameters to reliability function can be considered to be random variables with the wide range of different uncertainties. It can be possible to calculate the probabilities of failure according to the relative crest freeboard with the variations of the incident wave directions, the structural types of vertical breakwaters, and admissible overtopping volumes in conditions of the long and short crested-waves.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.3
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• pp.57-64
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• 1989

This study presents a reliability-based optimum design of reinforced concrete frames, in which the AFOSM and SOSM methods are applied for the evaluation of the failure probabilities, and the sequential linear programming method is used as a practical approach to the system optimization. One-story two-bay reinforced concrete frame is chosen for the numerical illustration of the proposed reliability-based optimum design. As a result, it is found that the proposed procedure for the reliability-based optimization of RC frames could provide the accurate estimation of the optimal level of safety, and appears applicable to real structures with reasonable complexity. It is shown in the paper that the probability distributions of the basic random variables and the uncertainties of the applied loadings and material strengths may have great effect on the optimum design, but the AFOSM and SOSM methods do not show significant discrepancy in the optimum design results, but the former appears more realistic and time saving than the latter for this specific study.

• Journal of Korean Society of Steel Construction
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• v.21 no.3
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• pp.331-342
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• 2009

A reliability analysis of the fatigue failure of highway steel bridges was performed by applying the Miner's fatigue damage rule for the fatigue design truck proposed for the LRFD code and for the current DB 24 truck. The limit state function for fatigue failure is expressed as a function of various random variables that affect fatigue damage. Among these variables, the statistical parameters for the equivalent moment, the impact factor, and the loadometer were obtained by analyzing recently measured domestic traffic data, and the parameters for the fatigue strength, the girder distribution factor, and the headway factor were obtained from the measured data reported in literature. Based on the reliability analysis, the fatigue truck model for the LRFD code was proposed. After applying the proposed fatigue truck to the LRFD code, 16 composite plate and box girder bridges were designed based on the LRFD method, and the LRFD design results for the fatigue limit state were compared with those by the current KHBDC.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.4 no.2
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• pp.13-19
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• 2008

In order to predict a remaining life of a plant, it is necessary to select the components that are critical to the plant life. The remaining life of those components shall be evaluated by considering the aging effect of materials used as well as numerous factors. However, when evaluating reliability of nuclear structural components, some problems are quite formidable because of lack of information such as operating history, material property change and uncertainty in damage models. Accordingly, if structural integrity and safety are evaluated by the deterministic fracture mechanics approach, it is expected that the results obtained are too conservative to perform a rational evaluation of plant life. The probabilistic fracture mechanics approaches are regarded as appropriate methods to rationally evaluate the plant life since they can consider various uncertainties such as sizes and shapes of cracks and degradation of material strength due to the aging effects. The objective of this study is to evaluate the structural integrity for a reactor pressure vessel under the small break loss of coolant accident by applying the deterministic and probabilistic fracture mechanics. The deterministic fracture mechanics analysis was performed using the three dimensional finite element model. The probabilistic integrity analysis was based on the Monte Carlo simulation. The selected random variables are the neutron fluence on the vessel inside surface, the content of copper, nickel, and phosphorus in the reactor pressure vessel material, and initial RTNDT.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.4
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• pp.443-449
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• 2004

Methods for mixing variable types of steel fibers have been developed recently to suppress outbreak of crack or to control the width of crack and improve the load resistible capacity at the same time. On the other hand, uncertainty by complex nature of destruction dynamics of steel fiber reinforced concrete(SFRC) is included. In this study, analysis of reliance considering uncertainty of SFRC beam is done. For this, intensity limit state model was proposed. Moreover, characteristic values about almost every kinds of probability variables were collected and presented according to home and foreign references. Process of improving uncertainty from the result of experiments by Bayseian updating method is also proposed on the purpose of offering better statistical characteristic values with more data in the new future. Fatigue fracture probability equation is proposed and needed statistical characteristic values were presented to analyze fatigue reliance

• Geotechnical Engineering
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• v.2 no.3
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• pp.37-50
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• 1986

The uncertainties encountered in the stability analysis for the foundation of offshore structures on clay are formulated in probabilistic terms and used to evaluate the reliability of the foundation design. The major sources of uncertainty are: soil properties, f.ave loads, and methods of analysis. The major part of the uncertainty in safety factor is contributed by the uncertainty in the undrained shear strength. All sources of uncertainties that affect the shear strength of clay are modeled and systematically analyzed. The in situ undrained shear strengths are evaluated by laboratory tests and cone penetration tests. The undrained shear strengths from the laboratory test and CPT, respectively at Statfjord B site in the North Sea, are used as an example in risk analysis. Using the CPT alone, the failure probability on sliding of gravity platform at Statfjord B is much larger than the failure probability using the laboratory undrained shear strengths. The major uncertainty of using the CPT as the estimate of th2 undrained shear strength of clay results from the correlation between the cone resistance and the undrained shear strength.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.111-115
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• 2014

Effect of dynamic electric fields on dielectric breakdown behavior in Cu damascene interconnects was investigated. Among the DC, unipolar, and bipolar pulse conditions, the longest dielectric lifetime is observed under the bipolar condition because backward Cu ion drift occurs when the direction of electric field is changed by 180 degrees and Cu contamination is prohibited as a results. Under the unipolar pulse condition, the dielectric lifetime increases as pulse frequency increases and it exceed the lifetime under DC condition. It suggests that the intrinsic breakdown of dielectrics significantly affect the dielectric breakdown in addition to Cu contamination. As the unipolar pulse width decreases, dielectric bond breakdown is more difficult to occur.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.4
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• pp.355-362
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• 2008

A reliability model of Level II AFDA is proposed to analyze the wave run-up occurring by the interaction of incident waves and sloped coastal structures. The reliability model may be satisfactorily calibrated by Level III Monte-Carlo simulation. Additionally, the partial safety factors of random variables related to wave run-up can be straightforwardly evaluated by the inverse-reliability method that use influence coefficients and uncertainties of random variables, and target probability of failure. In particular, a design equation for wave run-up is derived in the same form as that of deterministic design method so that the reliability-based design method of Level I may be applied easily. Finally, it is confirmed that results redesigned by the reliability-based design method of Level I with partial safety factors suggested in this paper are satisfactorily compared with results of CEM(2006) as well as those of Level II AFDA.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.4
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• pp.461-466
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• 2013

Advanced fiber-reinforced laminated composites are widely used in various fields of engineering to reduce weight. The material property of each ply is well known; specifically, it is known that ply is less reliable than metallic materials and very sensitive to the loading direction. Therefore, it is important to consider this uncertainty in the design of laminated composites. In this study, reliability analysis is conducted using COMSOL and MATLAB interactions for a laminated composite plate for the case in which the tip deflection is the design requirement and the material property is a random variable. Furthermore, the efficiency and accuracy of the approximation method is identified, and a probabilistic sensitivity analysis is conducted. As a result, we can prove the applicability of the advanced design method for the stabilizer of an underwater vehicle.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.4
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• pp.217-226
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• 1993

This study is related to the surface subsidence due to the collapse of a underground void during earthquakes. The amount of the settlement due to the collapse of a underground void will depend on the depth of the void, the initial condition of unit weight of sand, the size and type of foundation, the strength of earthquake, the size of a void, etc. The purpose of the paper is to estimate the amount of the subsidence, analyse the factors affecting the subsidence, and develop a program determining the probability of the damages to structures in terms of absolute and differential settlement and rotational settlement. On the base of the results obtained in this study, when the depth of a void is constant and the width of the void increases, the change of the subsidence factor due to the angle of internal friction and the actual effective factor of the void become smaller than that due to the unit weight of sand deposits. In the same condition, the probabilities of damages due to the absolute and differential settlement increase, and those due to the rotational settlement decrease.