• 한국신뢰성학회지:신뢰성응용연구
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• 제1권1호
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• pp.47-54
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• 2001

This paper considers the parameter estimation problem of the failure intensity function and maintenance effect in a repairable system. We propose estimation procedures for repairable systems on which preventive maintenance is performed. The failure process is modeled by a proportional age reduction model [Brown, Mahoney and Sivazlian(1983)] which is useful to model the imperfect effect of preventive maintenance. When failure and maintenance (preventive) times are given, the maximum likelihood method is used to estimate the maintenance effect and the parameters of intensity function, simultaneously We obtain the maximum likelihood estimators using a genetic algorithm. A numerical example is also presented.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1616-1629
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• 2023

To quantify the conservatism of existing ASME strain-based evaluation methods for seismic loading, this paper presents very low cycle fatigue test data of elbows under various cyclic loading conditions and comparison of evaluation results with experimental failure cycles. For strain-based evaluation methods, the method presented in ASME BPVC CC N-900 and Sec. VIII are used. Predicted failure cycles are compared with experimental failure cycle to quantify the conservatism of evaluation methods. All methods give very conservative failure cycles. The CC N-900 method is the most conservative and prediction results are only ~0.5% of experimental data. For Sec. VIII method, the use of the option using code tensile properties gives ~3% of experimental data, and the use of the material-specific reduction of area can reduce conservatism but still gives ~15% of experimental data.

• 한국안전학회지
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• 제35권6호
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• pp.1-8
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• 2020

In recent years, hydrogen has received much attention as an alternative energy source to fossil fuels. In order to ensure safety from the increasing number of hydrogen refueling stations, prevention methods have been required. In this regard, this study suggested an approach to reduce the risk of hydrogen refueling station by increasing Safety Integrity Level (SIL) for a Steam Methane Reformer (SMR) in On-Site Hydrogen Refueling Station. The worst scenario in the SMR was selected by HAZOP and the required SIL for the worst scenario was identified by LOPA. To verify the required SIL, the PFDavg.(1/RRF) of Safety Instrumented System (SIS) in SMR was calculated by using realistic failure rate data of SIS. Next, several conditions were tested by varying the sensor redundancy and proof test interval reduction and their effects on risk reduction factor were investigated. Consequently, an improved condition, which were the redundancy of two-out-of-three and the proof test interval of twelve months, achieved the tolerable risk resulting in the magnitude of risk reduction factor ten times greater than that of the baseline condition.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.201-206
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• 2001

This paper presents truss model that can be used to determine the deformation as well as strength of RC members. This model is constituted to address plastic hinge rotation at tile deformation concentrated regions under severe lateral load. The behavior of each element of truss model is evaluated on the basis of stress field analysis. The deformation is obtained by combining element deformations with joint rotation. Initial strength is calculated at the first failure of any element, and strength deterioration after failure depends on the strength reduction of this element. The proposed model will provide useful tools in seismic design of ductility-required members.

• 한국경영과학회지
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• 제25권4호
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• pp.45-54
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• 2000

Estimation Problems of parameters of the failure process and the repair effect in repairable systems are considered. We propose estimation procedures in repairable systems without preventive maintenances. The failure process is modeled by a proportional age reduction model (Brown, Mahoney, Sivazlian [5]) which is able to consider both aging and repair effects. Maximum likelihood method is used to estimate the repair effect and parameters of intensity function simultaneously. simulations are performed to evaluate the accuracy of estimators. A numerical example is also presented.

• International Journal of Reliability and Applications
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• 제7권2호
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• pp.111-125
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• 2006

This paper introduces different vectors of the reliability equivalence factors of a series system consists of n independent and nonidentical components. The failure rates of the system components are assumed to be constant. The reliability function and mean time to failure are used as performances to derive the reliability equivalences of the system. The results presented here generalize those available in the literatures. Numerical study is given to explain how one can utilize the theoretical results obtained.

• Journal of Mechanical Science and Technology
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• 제18권4호
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• pp.582-591
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• 2004

The purpose of this study was to determine the effects of elbow joint angle on mechanical properties, as represented by ultimate load, failure strain and elastic modulus, of bone-tendon specimens of common extensor tendon of the humeral epicondyle. Eight pairs of specimens were equally divided into two groups of 8 each, which selected arbitrarily from left or right side of each pair, positioned at 45$^{\circ}$ and 90$^{\circ}$ of elbow flexion and subjected to tension to failure in the physiological direction of the common extensor tendon. For comparison of the differences in the failure and elastic modulus between tendon and the bone-junction, data for both were evaluated individually. Significant reduction in ultimate load of bone-tendon specimens was shown to occur at 45$^{\circ}$. The values obtained from the bone-tendon junctions with regard to the failure strain were significant higher than those from tendon in both loading directions, but the largest failure strain at the bone-tendon junction was found at 45$^{\circ}$. The elastic modulus was found to decrease significantly at the bone-tendon junction when the loading direction switched from 90$^{\circ}$ to 45$^{\circ}$. Histological observation, after mechanical tensile tests, in both loading directions showed that failure occurred at the interface between tendon and uncalcified fibrocartilage in the thinnest fibrocartilage zone of the bone-tendon junction. We concluded that differences in measured mechanical properties are a consequence of varying the loading direction of the tendon across the bone-tendon specimen.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.811-818
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• 2005

Stability analyses on the 17 railroad cut-off soil slopes were carried out. The influences of rainfall infiltration on the slope stabilities were taken into account by seepage analyses using finite element method and by assuming ground water tables to be located adjacent to soil surface. The validity of those analyses were evaluated by comparing the slope failure characteristics between analysis results and the past failure records. The analyses were not appropriate to estimate the failure surface and the method considering only the increase of pore-water pressure (reduction of matric suction) as the influence of rainfall cannot appropriately estimate the surficial failures that occurred most of the cut-off soil slopes. For the better estimation of the surficial failure, the influence of water flows over slope surface which erode soil mass and/or increase driving force, should be evaluated and considered.

• Steel and Composite Structures
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• 제22권5호
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• pp.1055-1071
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• 2016

The paper presents an innovative steel moment frame with the replaceable reinforced concrete wall panel (SRW) structural system, in which the replaceable concrete wall can play a role to increase the overall lateral stiffness of the frame system. Two full scale specimens composed of the steel frames and the replaceable reinforced concrete wall panels were tested under the cyclic horizontal load. The failure mode, load-displacement response, deformability, and the energy dissipation capacity of SRW specimens were investigated. Test results show that the two-stage failure mode is characterized by the sequential failure process of the replaceable RC wall panel and the steel moment frame. It can be found that the replaceable RC wall panels damage at the lateral drift ratio greater than 0.5%. After the replacement of a new RC wall panel, the new specimen maintained the similar capacity of resisting lateral load as the previous one. The decrease of the bearing capacity was presented between the two stages because of the connection failure on the top of the replaceable RC wall panel. With the increase of the lateral drift, the percentage of the lateral force and the overturning moment resisted by the wall panel decreased for the reason of the reduction of its lateral stiffness. After the failure of the wall panel, the steel moment frame shared almost all the lateral force and the overturning moment.

• 품질경영학회지
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• 제40권2호
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• pp.186-198
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• 2012

Since Duncan(1956) first proposed an economic design of $\bar{X}$-control charts, most of the succeeding works on economic design of control charts assumed the exponential failure model like Duncan. Hu(1984), however, assumed a more versatile Weibull failure model to develop an economic design of $\bar{X}$-control charts and Banerjee and Rahim(1988) further improved Hu's design by changing the assumption of fixed-length sampling intervals to variable-length ones. In this article we follow the approach of Banerjee and Rahim(1988) but include a pair of warning limits inside the control limits in order to search for a failure without stopping the process when the sample mean falls between warning and control limits. The computational results indicate that the proposed model gives a lower cost than Banerjee and Rahim's model unless the early failure probability of a Weibull distribution is relatively large. The reduction in cost is shown to become larger as the cost of production loss outweighs the cost of searches for a failure.