• Smart Structures and Systems
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• v.14 no.5
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• pp.847-867
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• 2014

There are continuous efforts to mitigate structural losses from earthquakes and manage risk through seismic risk assessment; seismic fragility curves are widely accepted as an essential tool of such efforts. Seismic fragility curves can be classified into four groups based on how they are derived: empirical, judgmental, analytical, and hybrid. Analytical fragility curves are the most widely used and can be further categorized into two subgroups, depending on whether an analytical function or simulation method is used. Although both methods have shown decent performances for many seismic fragility problems, they often oversimplify the given problems in reliability or structural analyses owing to their built-in assumptions. In this paper, a new method is proposed for the development of seismic fragility curves. Integration with sophisticated software packages for reliability analysis (FERUM) and structural analysis (ZEUS-NL) allows the new method to obtain more accurate seismic fragility curves for less computational cost. Because the proposed method performs reliability analysis using the first-order reliability method, it provides component probabilities as well as useful byproducts and allows further fragility analysis at the system level. The new method was applied to a numerical example of a 2D frame structure, and the results were compared with those by Monte Carlo simulation. The method was found to generate seismic fragility curves more accurately and efficiently. Also, the effect of system reliability analysis on the development of seismic fragility curves was investigated using the given numerical example and its necessity was discussed.

• Korean Journal of Metals and Materials
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• v.49 no.4
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• pp.275-280
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• 2011

This paper focuses on reliability prediction of long-term creep strength for Modified 9Cr-1Mo steel (Gr. 91) which is considered as one of the structural materials of next generation reactor systems. A "Z-parameter" method was introduced to describe the magnitude of standard deviation of creep rupture data to the master curve which can be plotted by log stress vs. The larson-Miller parameter (LMP). Statistical analysis showed that the scattering of the Z-parameter for the Gr. 91 steel well followed normal distribution. Using this normal distribution of the Z-parameter, the various reliability curves for creep strength design, such as stress-time temperature parameter reliability curves (${\sigma}$-TTP-R curves), stress-rupture time-reliability curves (${\sigma}-t_{r}-R$ curves), and allowable stress-temperature- reliability curves ([${\sigma}$]-T-R curves) were reasonably drawn, and their results are discussed.

• Journal of Communications and Networks
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• v.11 no.5
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• pp.445-454
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• 2009

Cooperative transmission protocols are always designed to achieve the largest diversity gain and the network capacity simultaneously. The concept of diversity-multiplexing tradeoff (DMT) in multiple input multiple output (MIMO) systems has been extended to this field. However, DMT constrains a better understanding of the asymptotic interplay between transmission rate, outage probability (OP) and signal-to-noise ratio. Another formulation called the throughput-reliability tradeoff (TRT) was then proposed to avoid such a limitation. By this new rule, Azarian and Gamal well elucidated the asymptotic trends exhibited by the OP curves in block-fading MIMO channels. Meanwhile they doubted whether the new rule can be used in more general channels and protocols. In this paper, we will prove that it does hold true in decode-and-forward cooperative protocols. We deduce the theoretic OP curves predicted by TRT and demonstrate by simulations that the OP curves will asymptotically overlap with the theoretic curves predicted by TRT.

• Steel and Composite Structures
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• v.39 no.3
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• pp.243-259
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• 2021

In the present paper, a Monte Carlo-based framework is developed to investigate the accuracy and reliability of analytical fragility curves of steel moment-resisting frames and simple SDOF systems. It is also studied how the effectiveness of incremental dynamic analysis (IDA) and multiple stripes analysis (MSA) approaches, as two common nonlinear dynamic analysis methods, are influenced by the number of records and analysis stripes in fragility curves producing. Results showed that the simple SDOF systems do not provide accurate and reliable fragility curves compared with realistic steel moment-resisting structures. It is demonstrated that, the effectiveness of nonlinear dynamic analysis approaches is dependent on the fundamental period of structures, where in short-period structures, IDA is found to be more effective approach compared with MSA. This difference between the effectiveness of two analysis approaches decreases as the fundamental period of structures become longer. Using of 2 or 3 analysis stripes in MSA approach leads to significant inaccuracy and unreliability in the estimated fragility curves. Additionally, 15 number of ground motion records is recommended as a threshold of significant unreliability in estimated fragility curves, constructed by MSA.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.29 no.1
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• pp.143-150
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• 2006

Box-Cox model and T-factor method have been widely used to measure economic depreciations for industrial property. The Box-Cox model which combines economic efficiency with depreciation pattern is here extended to the reliability function. To do so a Rayleigh distribution which has been used to estimate the reliability of current assets was chosen as an efficiency curve of marginal productivity. Such an approach provides the possibility to classify the efficiency curves into four categories. It is also possible to analyze the types of depreciation curves. Therefore, the power family of a non-linear Box-Cox model could be set at certain constant values, then the model can be transformed into a linear model to estimate the economic depreciation rates by utilizing the reliability function. Estimating the resultant linear regression equation requires minimal number of observations, while at the same time facilitating the test of hypothesis on depreciation rates.

• Earthquakes and Structures
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• v.8 no.2
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• pp.443-462
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• 2015

Some model building codes stipulate that the design displacement of a building can be computed using the elastic static analysis results multiplied by the deflection amplification factor, $C_d$. This approach for estimating the design displacement is essential and appealing in structural engineering practice when nonlinear response history analysis (NRHA) is not required. Furthermore, building codes stipulate the consideration of accidental torsion effects using accidental eccentricity, whether the buildings are symmetric-plan, or asymmetric-plan. In some model building codes, the accidental eccentricity is further amplified by the torsional amplification factor $A_x$ in order to minimize the discrepancy between statically and dynamically estimated responses. Therefore, this warrants exploration of the reliability of statically estimated design displacements in accordance with the building code requirements. This study uses the discrepancy curves as a way of assessing the reliability of the design displacement estimates resulting from the factors $C_d$ and $A_x$. The discrepancy curves show the exceedance probabilities of the differences between the statically estimated design displacements and NRHA results. The discrepancy curves of 3-story, 9-story, and 20-story example buildings are investigated in this study. The example buildings are steel special moment frames with frequency ratios equal to 0.7, 1.0, 1.3, and 1.6, as well as existing eccentricity ratios ranging from 0% to 30%.

• Wind and Structures
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• v.23 no.1
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• pp.75-90
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• 2016

A probabilistic approach that combines structural demand hazard analysis with cumulative damage assessment is presented and applied to a steel tower of a wind turbine. The study presents the step by step procedure to compare the reliability over time of the structure subjected to fatigue, assuming: a) a binomial Weibull annual wind speed, and b) a traditional Weibull probability distribution function (PDF). The probabilistic analysis involves the calculation of force time simulated histories, fatigue analysis at the steel tower base, wind hazard curves and structural fragility curves. Differences in the structural reliability over time depending on the wind speed PDF assumed are found, and recommendations about selecting a real PDF are given.

• Structural Engineering and Mechanics
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• v.3 no.3
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• pp.201-213
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• 1995

At present Level 2 and importance sampling methods are the main tools used to estimate reliability of structural systems. But sometimes application of these techniques to realistic problems involves certain difficulties. In order to overcome the difficulties it is suggested to use Monte Carlo simulation in combination with two other techniques-extreme value and tail entropy approximations; an appropriate Pearson's curve is fit to represent simulation results. On the basis of this approach an algorithm and computer program for structural reliability estimation are developed. A number of specially chosen numerical examples are considered with the aim of checking the accuracy of the approach and comparing it with the Level 2 and importance sampling methods. The field of application of the approach is revealed.

• Computers and Concrete
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• v.29 no.1
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• pp.59-67
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• 2022

In this paper, a reliability-based approach has been implemented to develop seismic analytical fragility curves of highway bridges. A typical bridge class of the Central and South-eastern United States (CSUS) region was selected. Detailed finite element modelling is presented and Incremental Dynamic Analysis (IDA) is used to capture the behavior of the bridge from linear to nonlinear behavior. Bayesian linear regression method is used to define the demand model. A reliability approach is implemented to generate the analytical fragility curves and the proposed approach is compared with the conventional fragility analysis procedure.

• KCID journal
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• v.4 no.2
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• pp.10-24
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• 1997

This study is to analyse the reliability of storm sewer in urban area by applying the reliability analysis method. Two methods (MVFOSM and AFOSM) are applied to 6 drainage area in Seoul city and risk-safety factor curves are derived. Because risk-safety f