• Structural Engineering and Mechanics
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• v.83 no.5
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• pp.577-591
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• 2022

This paper develops a comparatively time-efficient methodology for performing seismic fragility analysis of the reinforced concrete (RC) buildings in the presence of uncertainty sources. It aims to appraise the effectiveness of any variation in the material's mechanical properties as epistemic uncertainty, and the record-to-record variation as aleatory uncertainty in structural response. In this respect, the fuzzy set theory, a well-known 𝛼-cut approach, and the Genetic Algorithm (GA) assess the median of collapse fragility curves as a fuzzy response. GA is requisite for searching the maxima and minima of the objective function (median fragility herein) in each membership degree, 𝛼. As this is a complicated and time-consuming process, the authors propose utilizing the Gene Expression Programming-based (GEP-based) equation for reducing the computational analysis time of the case study building significantly. The results indicate that the proposed structural analysis algorithm on the derived GEP model is able to compute the fuzzy median fragility about 33.3% faster, with errors less than 1%.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.4
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• pp.1-12
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• 2011

Seismic fragility analysis has been developed to evaluate the seismic performance of existing nuclear power plants, but now its applicability has been extended to buildings and bridges. In general, the seismic fragility curves are evaluated from the nonlinear time-history analysis (THA) using many earthquake ground motions. Seismic fragility analysis using the nonlinear THA requires a time consuming process of structural modeling and analysis. To overcome this shortcoming of the nonlinear THA, simplified methods such as the displacement coefficient method (DCM) and the capacity spectrum method (CSM) are used for the seismic fragility analysis. In order to evaluate the accuracy of the seismic fragility curve calculated by the DCM and the CSM, the seismic fragility curves of a reinforced concrete shear wall structure calculated by the DCM and CSM are compared with those calculated by the nonlinear THA. In order to construct a numerical fragility curve, 190 artificially generated ground motions corresponding to the design spectrum and the methodology proposed by Shinozuka et al. are used.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.1 s.47
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• pp.63-74
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• 2006

The seismic fragility analysis method has been used as a quantitative seismic safety evaluation method for the NPP(Nuclear Power Plant) structures and equipments. The seismic fragility analysis gives a realistic seismic capacity excluding the convertism included in the design stage. The conservatism is considered as the probabilistic parameters related to the response and capacity in the seismic fragility analysis. In this study, the displacement based seismic fragility analysis method was proposed based on the nonlinear dynamic analysis results. In this study, the seismic safety of the prestressed concrete containment building of KSNP(Korean Standard Nuclear Power Plant) was evaluated for the scenario earthquakes, neat-fault, far-fault, design earthquake and probability based scenario earthquake, which can be occurred in the NPP sites.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.4
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• pp.155-162
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• 1999

This paper presents a generation of analytical fragility curves for bridge. The analytical fragility curves are constructed on the basis of nonlinear dynamic analysis. Two-parameter lognormal distribution functions are used to represent the fragility curves with the parameters estimated by the maximum likelihood method. To demonstrate the development of analytical fragility curves, two of representative bridges with a precast prestressed continuous deck in the Memphis. Tennessee area are used.

• International journal of steel structures
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• v.18 no.5
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• pp.1607-1616
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• 2018

Quantitatively modeling and propagating all sources of uncertainty stand at the core of seismic fragility assessment of structures. This paper investigates the effects of various sources of uncertainty on seismic responses and seismic fragility estimates of single-layer reticulated domes. Sensitivity analyses are performed to examine the sensitivity of typical seismic responses to uncertainties in structural modeling parameters, and the results suggest that the variability in structural damping, yielding strength, steel ultimate strain, dead load and snow load has significant effects on the seismic responses, and these five parameters should be taken as random variables in the seismic fragility assessment. Based on this, fragility estimates and fragility curves incorporating different levels of uncertainty are obtained on the basis of the results of incremental dynamic analyses on the corresponding set of 40 sample models generated by Latin Hypercube Sampling method. The comparisons of these fragility curves illustrate that, the inclusion of only ground motion uncertainty is inappropriate and inadequate, and the appropriate way is incorporating the variability in the five identified structural modeling parameters as well into the seismic fragility assessment of single-layer reticulated domes.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.226-232
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• 2000

Seismic probabilistic risk assessment(RA) rather than deterministic assessment provides more valuable information and insight for resolving seismic safety issues in nuclear power plant design. In the course of seismic PRA seismic fragility analysis is the most significant and essential phase especially for structural or mechanical engineers. Lately the seismic fragility analysis is taken as a useful tool in general structural engineering as well. A systemized and synthesized procedure or technology related to seismic fragility analysis of critical industrial facilities reflecting the unique experiences and database in Korea is urgently required. This paper gives a state-of-the-art reviews of PRA and briefly summarizes the technologies related to PRA and seismic fragility analysis before developing an unique technology considering characteristics of Korean database. Some key items to be resolved theoretically or technically are extracted and presented for the future research.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.220-227
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• 2002

This study introduces the fragility analysis method for the safety evaluation of reinforced concrete pier subject to earthquake. Damage probability is calculated instead of the failure probability from definition of the damage state in the fragility curve. Not only the damage model determined by the response of structure subject to earthquake, but also the plastic-damage model which can represent the local damage is applied to fragility analysis. The evaluation method of damage state by damage variable in global structure is defined by this procedure. This study introduces the fragility analysis method considering the features of nonlinear time history behavior of reinforced concrete element and the plastic behavior of materials. At last, This study gives one of the approach method for seismic margin evaluation with the result of fragility analysis to design seismic load.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.09a
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• pp.200-207
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• 2001

This paper introduces a methodology of seismic fragility analysis and discusses the basic input variables, focusing on the conservatism and variability of reference response spectrum. The procedures to consider the composite modal damping in the seismic fragility analysis is presented and its effects on the seismic capacity of structure is evaluated through an example analysis of the nuclear power plant structure which has typical composite modal damping characteristics. Two seismic fragility analyses were performed to obtain the seismic capacities which evaluated by considering the composite modal damping and the single damping characteristics. The results showed that the seismic fragility analysis without considering the different values of composite modal damping may considerably overestimate the seismic capacity of coupled structures.

• Earthquakes and Structures
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• v.25 no.4
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• pp.235-247
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• 2023

Bingöl, a city in eastern Türkiye, is located at a very close distance to the Karlıova Region which is a junction point of the North Anatolian Fault Zone and Eastern Anatolian Fault Zone. By bilateral step over of North Anatolian Fault Zone and Eastern Anatolian Fault Zone each other there occurred NorthWest-SouthEast extended right-lateral and NorthEast-SouthWest extended left-lateral fault zones. In this paper, a typical school building located in Bingöl Çeltiksuyu was selected as the case study. Information on the school building and Bingöl Earthquake (2003) have been given in the paper. This study aimed to determine the fragility curves of the school building according to HAZUS 2022, Turkish Seismic Codes 1998, 2007 and 2018. These codes have been introduced in terms of damage limits. Incremental dynamic analysis is a parametric analysis method that has recently emerged in several different forms to estimate more thoroughly structural performance under seismic loads. Fragility analysis is commonly using to estimate the damage probability of buildings. Incremental Dynamic Analysis have performed, and 1295 Incremental Dynamic Analysis output was evaluated to obtain fragility curves. 20 different ground motion records have been selected with magnitudes between 5.6M and 7.6M. Scaling factors of these ground motions were selected between 0.1g and 2g. Comparison has been made between HAZUS 2022 and Turkish Seismic Codes 1998, 2007 and 2018 in terms of damage states and how they affected fragility curves. TSC 1998 has more conservative strictions along with TSC 2018 than TSC2007 and HAZUS moderate and extensive damage limits.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.3
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• pp.149-158
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• 2022

As a bridge ages, its mechanical properties and structural performance deteriorate, degrading its seismic performance during a strong earthquake. In this study, the aging of piers and bridge bearings was quantified in several stages and reflected in the analysis model, enabling the evaluation of the member-level seismic fragility of these bearings. Moreover, by assuming that the failure mechanism of a bridge system is a series system, a method for evaluating the system-level seismic fragility based on the member-level seismic fragility analysis result is formulated and proposed. For piers with rubber and lead-rubber bearings (members vulnerable to aging effects), five quantitative degrees of aging (0, 5, 10, 25, and 40%) are assumed to evaluate the member-level seismic fragility. Then, based on the result, the system-level seismic fragility evaluation was implemented. The pier rather than the bridge bearing is observed to have a dominant effect on the system-level seismic fragility. This means that the seismic fragility of more vulnerable structural members has a dominant influence on the seismic fragility of the entire bridge system.