Closed-form fragility estimates, parameter sensitivity, and bayesian updating for RC columns / Do-Eun Choe in Journal of engineering mechanics, Vol. 133 N°7 (Juillet 2007)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.833–843. Titre : Closed-form fragility estimates, parameter sensitivity, and bayesian updating for RC columns Type de document : texte imprimé Auteurs : Do-Eun Choe, Auteur ; Paolo Gardoni, Auteur ; David Rosowsky, Auteur Année de publication : 2007 Article en page(s) : pp.833–843. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Bridges Concrete columns Shear Deformation Bayesian analysis Sensitivity Probabilistic models Parameters Résumé : Reinforced concrete (RC) columns are the most critical components in bridges under seismic excitation. In this paper, a simple closed-form formulation to estimate the fragility of RC columns is developed. The formulation is used to estimate the conditional probability of failure of an example column for given shear and deformation demands. The estimated fragilities are as accurate as more sophisticated estimates (i.e., predictive fragilities) and do not require any reliability software. A sensitivity analysis is carried out to identify to which parameter(s) the reliability of the example column is most sensitive. The closed-form formulation uses probabilistic capacity models. A Bayesian procedure is presented to update existing probabilistic models with new data. The model updating process can incorporate different types of information, including laboratory test data, field observations, and subjective engineering judgment, as they become available. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2883 [...] [article] Closed-form fragility estimates, parameter sensitivity, and bayesian updating for RC columns [texte imprimé] / Do-Eun Choe, Auteur ; Paolo Gardoni, Auteur ; David Rosowsky, Auteur . - 2007 . - pp.833–843. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°7 (Juillet 2007) . - pp.833–843. Mots-clés : Bridges Concrete columns Shear Deformation Bayesian analysis Sensitivity Probabilistic models Parameters Résumé : Reinforced concrete (RC) columns are the most critical components in bridges under seismic excitation. In this paper, a simple closed-form formulation to estimate the fragility of RC columns is developed. The formulation is used to estimate the conditional probability of failure of an example column for given shear and deformation demands. The estimated fragilities are as accurate as more sophisticated estimates (i.e., predictive fragilities) and do not require any reliability software. A sensitivity analysis is carried out to identify to which parameter(s) the reliability of the example column is most sensitive. The closed-form formulation uses probabilistic capacity models. A Bayesian procedure is presented to update existing probabilistic models with new data. The model updating process can incorporate different types of information, including laboratory test data, field observations, and subjective engineering judgment, as they become available. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A7%2883 [...]

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Fragility increment functions for deteriorating reinforced concrete bridge columns / Do-Eun Choe in Journal of engineering mechanics, Vol. 136 N° 8 (Août 2010)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 136 N° 8 (Août 2010) . - pp. 969-978 Titre : Fragility increment functions for deteriorating reinforced concrete bridge columns Type de document : texte imprimé Auteurs : Do-Eun Choe, Auteur ; Paolo Gardoni, Auteur ; David Rosowsky, Auteur Article en page(s) : pp. 969-978 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Reinforced concrete Concrete columns Corrosion Bridges Degradation Seismic effects Life cycles Risk management. Résumé : The increased deformation and shear fragilities of corroding RC bridge columns subject to seismic excitations are modeled as functions of time using fragility increment functions. These functions can be applied to various environmental and material conditions by means of controlling parameters that correspond to the specific condition. For each mode of failure, the fragility of a deteriorated column at any given time is obtained by simply multiplying the initial fragility of the pristine/nondeteriorated column by the corresponding function developed in this paper. The developed increment functions account for the effects of the time-dependent uncertainties that are present in the corrosion model as well as in the structural capacity models. The proposed formulation is a useful tool for engineering practice because the fragility of deteriorated columns is obtained without any extra reliability analysis once the fragility of the pristine column is known. The fragility increment functions are expressed as functions of time t and a given deformation or shear demand. Unknown parameters involved in the models are estimated using a Bayesian updating framework. A model selection is conducted during the assessment of the unknown parameters using the Akaike information criterion and the Bayesian information criterion. For the estimation of the parameters, a set of data are obtained by first-order reliability method analysis using existing probabilistic capacity models for corroding RC bridge columns. Example fragilities of a deteriorated bridge column typical of current California's practice are presented to demonstrate the developed methodology. The increment functions suggested in this paper can be used to assess the time-variant fragility for application to life cycle cost analysis and risk analysis. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Fragility increment functions for deteriorating reinforced concrete bridge columns [texte imprimé] / Do-Eun Choe, Auteur ; Paolo Gardoni, Auteur ; David Rosowsky, Auteur . - pp. 969-978. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 8 (Août 2010) . - pp. 969-978 Mots-clés : Reinforced concrete Concrete columns Corrosion Bridges Degradation Seismic effects Life cycles Risk management. Résumé : The increased deformation and shear fragilities of corroding RC bridge columns subject to seismic excitations are modeled as functions of time using fragility increment functions. These functions can be applied to various environmental and material conditions by means of controlling parameters that correspond to the specific condition. For each mode of failure, the fragility of a deteriorated column at any given time is obtained by simply multiplying the initial fragility of the pristine/nondeteriorated column by the corresponding function developed in this paper. The developed increment functions account for the effects of the time-dependent uncertainties that are present in the corrosion model as well as in the structural capacity models. The proposed formulation is a useful tool for engineering practice because the fragility of deteriorated columns is obtained without any extra reliability analysis once the fragility of the pristine column is known. The fragility increment functions are expressed as functions of time t and a given deformation or shear demand. Unknown parameters involved in the models are estimated using a Bayesian updating framework. A model selection is conducted during the assessment of the unknown parameters using the Akaike information criterion and the Bayesian information criterion. For the estimation of the parameters, a set of data are obtained by first-order reliability method analysis using existing probabilistic capacity models for corroding RC bridge columns. Example fragilities of a deteriorated bridge column typical of current California's practice are presented to demonstrate the developed methodology. The increment functions suggested in this paper can be used to assess the time-variant fragility for application to life cycle cost analysis and risk analysis. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

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Probabilistic seismic demand models and fragility estimates for reinforced Concrete bridges with two-column bents / Jinquan Zhong in Journal of engineering mechanics, Vol. 134 n°6 (Juin 2008)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp.495–504. Titre : Probabilistic seismic demand models and fragility estimates for reinforced Concrete bridges with two-column bents Type de document : texte imprimé Auteurs : Jinquan Zhong, Auteur ; Paolo Gardoni, Auteur ; David Rosowsky, Auteur Année de publication : 2008 Article en page(s) : pp.495–504. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Bridges Concrete Structural reliability Bayesian analysis Seismic effects Columns Deformation Résumé : Probabilistic models are developed to predict the deformation and shear demands due to seismic excitation on reinforced concrete (RC) columns in bridges with two-column bents. A Bayesian methodology is used to develop the models. The models are unbiased and properly account for the predominant uncertainties, including model errors, arising from a potentially inaccurate model form or missing variables, measurement errors, and statistical uncertainty. The probabilistic models developed are akin to deterministic demand models and procedures commonly used in practice, but they have additional correction terms that explicitly describe the inherent systematic and random errors. Through the use of a set of “explanatory” functions, terms that correct the bias in the existing deterministic demand models are identified. These explanatory functions provide insight into the underlying behavioral phenomena and provide a means to select ground motion parameters that are most relevant to the seismic demands. The approach takes into account information gained from scientific/engineering laws, observational data from laboratory experiments, and simulated data from numerical dynamic responses. The demand models are combined with previously developed probabilistic capacity models for RC bridge columns to objectively estimate the seismic vulnerability of bridge components and systems. The vulnerability is expressed in terms of the conditional probability (or fragility) that a demand quantity (deformation or shear) will be greater than or equal to the corresponding capacity. Fragility estimates are developed for an example RC bridge with two-column bents, designed based on the current specifications for California. Fragility estimates are computed at the individual column, bent, and bridge system levels, as a function of the spectral acceleration and the ratio between the peak ground velocity and the peak ground acceleration. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A6%2849 [...] [article] Probabilistic seismic demand models and fragility estimates for reinforced Concrete bridges with two-column bents [texte imprimé] / Jinquan Zhong, Auteur ; Paolo Gardoni, Auteur ; David Rosowsky, Auteur . - 2008 . - pp.495–504. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp.495–504. Mots-clés : Bridges Concrete Structural reliability Bayesian analysis Seismic effects Columns Deformation Résumé : Probabilistic models are developed to predict the deformation and shear demands due to seismic excitation on reinforced concrete (RC) columns in bridges with two-column bents. A Bayesian methodology is used to develop the models. The models are unbiased and properly account for the predominant uncertainties, including model errors, arising from a potentially inaccurate model form or missing variables, measurement errors, and statistical uncertainty. The probabilistic models developed are akin to deterministic demand models and procedures commonly used in practice, but they have additional correction terms that explicitly describe the inherent systematic and random errors. Through the use of a set of “explanatory” functions, terms that correct the bias in the existing deterministic demand models are identified. These explanatory functions provide insight into the underlying behavioral phenomena and provide a means to select ground motion parameters that are most relevant to the seismic demands. The approach takes into account information gained from scientific/engineering laws, observational data from laboratory experiments, and simulated data from numerical dynamic responses. The demand models are combined with previously developed probabilistic capacity models for RC bridge columns to objectively estimate the seismic vulnerability of bridge components and systems. The vulnerability is expressed in terms of the conditional probability (or fragility) that a demand quantity (deformation or shear) will be greater than or equal to the corresponding capacity. Fragility estimates are developed for an example RC bridge with two-column bents, designed based on the current specifications for California. Fragility estimates are computed at the individual column, bent, and bridge system levels, as a function of the spectral acceleration and the ratio between the peak ground velocity and the peak ground acceleration. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A6%2849 [...]

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Stiffness degradation and time to cracking of cover concrete in reinforced concrete structures subject to corrosion / Jinquan Zhong in Journal of engineering mechanics, Vol. 136 N° 2 (Fevrier 2010)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 136 N° 2 (Fevrier 2010) . - pp. 209-219 Titre : Stiffness degradation and time to cracking of cover concrete in reinforced concrete structures subject to corrosion Type de document : texte imprimé Auteurs : Jinquan Zhong, Auteur ; Paolo Gardoni, Auteur ; David Rosowsky, Auteur Année de publication : 2010 Article en page(s) : pp. 209-219 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Cracking Energy Corrosion Reinforced concrete Stiffness Degradation Concrete structures Résumé : Corrosion-induced cracks in reinforced concrete (RC) structures degrade the stiffness of the cover concrete. The stiffness degradation is mainly caused by the softening in the stress-strain relation in the cracked concrete. Limited efforts have been made to model the cracking and the corresponding effects on the cover concrete, despite of its importance in assessing and modeling the behavior of RC structures. This paper proposes a stiffness degradation factor to model the stiffness degradation of the cover concrete subject to cracking. The proposed factor is computed in terms of the cracking strain corresponding to the maximum opening of the concrete cracks based on an energy principle applied to a fractured RC structure. The time to cracking of the cover concrete is then determined as the time from the corrosion initiation needed by the crack front to reach the outer surface of the cover concrete. The proposed stiffness degradation factor and the method to compute the time to cracking are illustrated through two numerical examples. The times to cracking of the cover concrete that are predicted using the proposed method are in agreement with the measured values from laboratory experiments. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Stiffness degradation and time to cracking of cover concrete in reinforced concrete structures subject to corrosion [texte imprimé] / Jinquan Zhong, Auteur ; Paolo Gardoni, Auteur ; David Rosowsky, Auteur . - 2010 . - pp. 209-219. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 2 (Fevrier 2010) . - pp. 209-219 Mots-clés : Cracking Energy Corrosion Reinforced concrete Stiffness Degradation Concrete structures Résumé : Corrosion-induced cracks in reinforced concrete (RC) structures degrade the stiffness of the cover concrete. The stiffness degradation is mainly caused by the softening in the stress-strain relation in the cracked concrete. Limited efforts have been made to model the cracking and the corresponding effects on the cover concrete, despite of its importance in assessing and modeling the behavior of RC structures. This paper proposes a stiffness degradation factor to model the stiffness degradation of the cover concrete subject to cracking. The proposed factor is computed in terms of the cracking strain corresponding to the maximum opening of the concrete cracks based on an energy principle applied to a fractured RC structure. The time to cracking of the cover concrete is then determined as the time from the corrosion initiation needed by the crack front to reach the outer surface of the cover concrete. The proposed stiffness degradation factor and the method to compute the time to cracking are illustrated through two numerical examples. The times to cracking of the cover concrete that are predicted using the proposed method are in agreement with the measured values from laboratory experiments. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

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