• Title, Summary, Keyword: fragility curves

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Analytical Fragility Curves for Bridge (교량의 해석적 손상도 곡선)

  • Lee, Jong-Heon
    • 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.

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A new methodology of the development of seismic fragility curves

  • Lee, Young-Joo;Moon, Do-Soo
    • 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.

Empirical Fragility Curves for Bridge (교량의 경험적 손상도 곡선)

  • Lee, Jong-Heon;Kim, Woon-Hak;Choi, Jung-Ho
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.6 no.1
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    • pp.255-262
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    • 2002
  • This paper presents a statistical analysis of empirical fragility curves for bridge. The empirical fragility curves are developed utilizing bridge damage data obtained from the 1995 Hyogoken Nanbu(Kobe) earthquake. Two-parameter lognormal distribution functions are used to represent the fragility curves with the parameters estimated by the maximum likelihood method. This paper also presents methods of testing the goodness of fit of the fragility curves and estimating the confidence intervals of the two parameters(median and log-standard deviation) of the distribution. An analytical interpretation of randomness and uncertainty associated with the median is provided.

Fragility Curve of Continuous Buried Pipeline subjected to Transverse Permanent Ground Deformation due to Liquefaction (액상화.횡방향 영구지반변형을 받는 연속된 지중매설관로의 구조적 손상도곡선 도출)

  • Kim, Tae-Wook;Lim, Yun-Mook
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.358-365
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    • 2006
  • In this study, fragility curves of continuous buried pipelines subjected to transverse PGD (permanent ground deformation) due to liquefaction are proposed. For the waterworks system, continuos buried pipelines made of ductile iron, poly ethylene, and poly vinyl chloride are analyzed and fragility curves are drawn. Fragility curves are based on the repetitive analyses results and formulated with the dominant factors of behaviour of buried pipeline. With the use of fragility curves, engineers can estimate the status of damage of buried pipeline without overall knowledge of relevant features. Especially, fragility curves proposed in this study will act as a major module of earthquake loss estimation method. Moreover, critical value of magnitude and width of transverse PGD (by which the full damage status of buried pipelines are induced) are estimated. With the use of regression curves of these values, pre evaluation of seismic safety of buried pipelines located within liquefaction hazardous region will be possible.

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Derivation of analytical fragility curves using SDOF models of masonry structures in Erzincan (Turkey)

  • Karimzadeh, Shaghayegh;Kadas, Koray;Askan, Aysegul;Erberik, M. Altug;Yakut, Ahmet
    • Earthquakes and Structures
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    • v.18 no.2
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    • pp.249-261
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    • 2020
  • Seismic loss estimation studies require fragility curves which are usually derived using ground motion datasets. Ground motion records can be either in the form of recorded or simulated time histories compatible with regional seismicity. The main purpose of this study is to investigate the use of alternative ground motion datasets (simulated and real) on the fragility curves. Simulated dataset is prepared considering regional seismicity parameters corresponding to Erzincan using the stochastic finite-fault technique. In addition, regionally compatible records are chosen from the NGA-West2 ground motion database to form the real dataset. The paper additionally studies the effects of hazard variability and two different fragility curve derivation approaches on the generated fragility curves. As the final step for verification purposes, damage states estimated for the fragility curves derived using alternative approaches are compared with the observed damage levels from the 1992 Erzincan (Turkey) earthquake (Mw=6.6). In order to accomplish all these steps, a set of representative masonry buildings from Erzincan region are analyzed using simplified structural models. The results reveal that regionally simulated ground motions can be used alternatively in fragility analyses and damage estimation studies.

Development of seismic fragility curves for high-speed railway system using earthquake case histories

  • Yang, Seunghoon;Kwak, Dongyoup;Kishida, Tadahiro
    • Geomechanics and Engineering
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    • v.21 no.2
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    • pp.179-186
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    • 2020
  • Investigating damage potential of the railway infrastructure requires either large amount of case histories or in-depth numerical analyses, or both for which large amounts of effort and time are necessary to accomplish thoroughly. Rather than performing comprehensive studies for each damage case, in this study we collect and analyze a case history of the high-speed railway system damaged by the 2004 M6.6 Niigata Chuetsu earthquake for the development of the seismic fragility curve. The development processes are: 1) slice the railway system as 200 m segments and assigned damage levels and intensity measures (IMs) to each segment; 2) calculate probability of damage for a given IM; 3) estimate fragility curves using the maximum likelihood estimation regression method. Among IMs considered for fragility curves, spectral acceleration at 3 second period has the most prediction power for the probability of damage occurrence. Also, viaduct-type structure provides less scattered probability data points resulting in the best-fitted fragility curve, but for the tunnel-type structure data are poorly scattered for which fragility curve fitted is not meaningful. For validation purpose fragility curves developed are applied to the 2016 M7.0 Kumamoto earthquake case history by which another high-speed railway system was damaged. The number of actual damaged segments by the 2016 event is 25, and the number of equivalent damaged segments predicted using fragility curve is 22.21. Both numbers are very similar indicating that the developed fragility curve fits well to the Kumamoto region. Comparing with railway fragility curves from HAZUS, we found that HAZUS fragility curves are more conservative.

Seismic Fragility Analysis Utilizing PDF Interpolation Technique (확률밀도함수 보간에 의한 교량의 지진취약도 분석)

  • ;;;Shigeru Kushiyama
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.495-502
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    • 2003
  • This study proposed the Probability Density Function (PDF) interpolation technique to evaluate the seismic fragility curves as a function of the return period. Seismic fragility curves have been developed as a function of seismic intensities such as peak ground acceleration, peak pound velocity, and pseudo-velocity spectrum. The return period of design earthquakes, however, can be more useful among those seismic intensity measurements, because the seismic hazard curves are generally represented with a return period of design earthquakes and the seismic design codes also require to consider the return period of design earthquake spectrum for a specific site. In this respect the PDF interpolation technique is proposed to evaluate the seismic fragility curves as a function of return period. Seismic fragility curves based on the return period are compared with ones based on the peak ground acceleration for the bridge model.

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Analytical fragility curves for typical Algerian reinforced concrete bridge piers

  • Kibboua, Abderrahmane;Naili, Mounir;Benouar, Djillali;Kehila, Fouad
    • Structural Engineering and Mechanics
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    • v.39 no.3
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    • pp.411-425
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    • 2011
  • This paper illustrates the results of a seismic vulnerability study aimed to derive the fragility curves for typical Algerian reinforced concrete bridge piers using an analytical approach. Fragility curves express the probability of exceeding a certain damage state for a given ground motion intensity (e.g., PGA). In this respect, a set of 41 worldwide accelerometer records from which, 21 Algerian strong motion records are included, have been used in a non-linear dynamic response analyses to assess the damage indices expressed in terms of the bridge displacement ductility, the ultimate ductility, the cyclic loading factor and the cumulative energy ductility. Combining the damage indices defined for 5 damage rank with the ground motion indices, the fragility curves for the bridge piers were derived assuming a lognormal distribution.

Development of Fragility Curves of Concrete Bridges (콘크리트 교량의 손상도 곡선 개발)

  • 김상훈;김두희;서형렬;김종인
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.319-325
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    • 2003
  • The fragility curves of seismic retrofitted bridges by steel jacketing of bridge columns and restrainers at expansion joints after the 1994 Northridge earthquake are developed. Fragility curves are represented by lognormal distribution functions with two parameters(fragility parameters consisting of median and log-standard deviation) and developed as a function of peak ground acceleration (PGA). Two parameters in the lognormal distribution are estimated by the maximum likelihood method. The sixty ground acceleration time histories for Los Angeles area developed for FEMA SAC project are used for the dynamic analysis of the bridges and a computer code is developed to calculate hysterestic parameters of bridge columns before and after steel jacketing. The effect of retrofit is expressed in terms of the increase of the median value of the fragility curve for the retrofitted bridge from that of the bridge before retrofit. The comparison of fragility curves of the bridges before and after column retrofit demonstrates that the improvement of the bridges with steel jacketing on the seismic performance is excellent for the damage states defined in this study. The comparison of fragility curves of the bridges before and after restrainers at expansion joints also shows the improvement in the seismic performance of restrained bridges for the severe damage states.

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Seismic fragility of regular masonry buildings for in-plane and out-of-plane failure

  • Karantoni, Fillitsa;Tsionis, Georgios;Lyrantzaki, Foteini;Fardis, Michael N.
    • Earthquakes and Structures
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    • v.6 no.6
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    • pp.689-713
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    • 2014
  • The seismic vulnerability of stone masonry buildings is studied on the basis of their fragility curves. In order to account for out-of-plane failure modes, normally disregarded in past studies, linear static Finite Element analysis in 3D of prototype regular buildings is performed using a nonlinear biaxial failure criterion for masonry. More than 1100 analyses are carried out, so as to cover the practical range of the most important parameters, namely the number of storeys, percentage of side length in exterior walls taken up by openings, wall thickness, plan dimensions and number of interior walls, type of floor and pier height-to-length ratio. Results are presented in the form of damage and fragility curves. The fragility curves correspond well to the damage observed in masonry buildings after strong earthquakes and are in good agreement with other fragility curves in the literature. They confirm what is already known, namely that buildings with stiff floors or higher percentage of load-bearing walls are less vulnerable, and that large openings, taller storeys, larger number of storeys, higher wall slenderness and higher ratio of clear height to horizontal length of walls increase the vulnerability, but show also by how much.