Documents disponibles écrits par cet auteur

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]  in Journal 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 ; Gardoni, Paolo, Auteur ; Rosowsky, David, 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  analysis  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 ; Gardoni, Paolo, Auteur ; Rosowsky, David, 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  analysis  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 [...]

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]  in Journal 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 ; Gardoni, Paolo, 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 ; Gardoni, Paolo, 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 [...]

Modeling structural degradation of RC bridge columns subjected to earthquakes and their fragility estimates / Ramesh Kumar in Journal of structural engineering, Vol. 138 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of structural engineering > Vol. 138 N° 1 (Janvier 2012) . - pp. 42-51 Titre : Modeling structural degradation of RC bridge columns subjected to earthquakes and their fragility estimates Type de document : texte imprimé Auteurs : Ramesh Kumar, Auteur ; Gardoni, Paolo, Auteur Année de publication : 2012 Article en page(s) : pp. 42-51 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Structural  degradation  Probabilistic  models  Seismic  fragility  Bridge  columns Résumé : Current seismic design of bridges is based on “one-time” performance of the bridges during the design seismic event. However, there might be a considerable probability of observing more than one damaging earthquakes in a bridge’s service life. Bridge components are known to accumulate seismic damage and deterioration in their structural properties. In such a scenario, design criteria that account for the cumulative seismic damage of bridges over time and performance objectives that span more than one seismic event are needed. This paper computes the probability of occurrence of more than one damaging earthquake during a bridge’s service life. Furthermore, it investigates the importance of accounting for cumulative seismic damage in seismic design. This paper develops a probabilistic model to compute the degraded deformation capacity of flexural reinforced concrete (RC) bridge columns as a function of cumulative low-cycle fatigue damage incurred in the past earthquakes. The model is developed for flexural RC columns because low-cycle fatigue is most significant for such columns. The proposed model accounts for the degradation in the ultimate curvature capacity and deformation capacity of RC columns associated to low-cycle fatigue. The proposed model is calibrated by using data from cyclic-load analyses of RC columns performed by using the finite element method (FEM). The FEM model accounts for the cracking and pinching of RC sections to properly simulate the degradation process. Finally, the proposed model is used to assess the fragilities of RC bridge columns conditioning on the values of low-cycle fatigue damage and deformation demand. It is found that in seismically active regions there is a significant probability of observing more than one damaging earthquake in a bridge’s service life. Therefore, accounting for the cumulative seismic damage in the seismic design is important. It is also found that the cumulative seismic damage can significantly affect the reliability of bridge columns. The developed models are useful for a seismic design that properly accounts for long-term safety and reliability of bridges. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v138/i1/p42_s1?isAuthorized=no [article] Modeling structural degradation of RC bridge columns subjected to earthquakes and their fragility estimates [texte imprimé] / Ramesh Kumar, Auteur ; Gardoni, Paolo, Auteur . - 2012 . - pp. 42-51. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 138 N° 1 (Janvier 2012) . - pp. 42-51 Mots-clés : Structural  degradation  Probabilistic  models  Seismic  fragility  Bridge  columns Résumé : Current seismic design of bridges is based on “one-time” performance of the bridges during the design seismic event. However, there might be a considerable probability of observing more than one damaging earthquakes in a bridge’s service life. Bridge components are known to accumulate seismic damage and deterioration in their structural properties. In such a scenario, design criteria that account for the cumulative seismic damage of bridges over time and performance objectives that span more than one seismic event are needed. This paper computes the probability of occurrence of more than one damaging earthquake during a bridge’s service life. Furthermore, it investigates the importance of accounting for cumulative seismic damage in seismic design. This paper develops a probabilistic model to compute the degraded deformation capacity of flexural reinforced concrete (RC) bridge columns as a function of cumulative low-cycle fatigue damage incurred in the past earthquakes. The model is developed for flexural RC columns because low-cycle fatigue is most significant for such columns. The proposed model accounts for the degradation in the ultimate curvature capacity and deformation capacity of RC columns associated to low-cycle fatigue. The proposed model is calibrated by using data from cyclic-load analyses of RC columns performed by using the finite element method (FEM). The FEM model accounts for the cracking and pinching of RC sections to properly simulate the degradation process. Finally, the proposed model is used to assess the fragilities of RC bridge columns conditioning on the values of low-cycle fatigue damage and deformation demand. It is found that in seismically active regions there is a significant probability of observing more than one damaging earthquake in a bridge’s service life. Therefore, accounting for the cumulative seismic damage in the seismic design is important. It is also found that the cumulative seismic damage can significantly affect the reliability of bridge columns. The developed models are useful for a seismic design that properly accounts for long-term safety and reliability of bridges. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v138/i1/p42_s1?isAuthorized=no

Probabilistic capacity models and fragility estimates for reinforced concrete columns incorporating NDT data / Huang, Qindan in Journal of engineering mechanics, Vol. 135 N° 12 (Décembre 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1384-1392 Titre : Probabilistic capacity models and fragility estimates for reinforced concrete columns incorporating NDT data Type de document : texte imprimé Auteurs : Huang, Qindan, Auteur ; Gardoni, Paolo, Auteur ; Hurlebaus, Stefan, Auteur Article en page(s) : pp. 1384-1392 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Bridges  Probability  Nondestructive  tests  Concrete  columns  Reinforced  concrete. Résumé : Knowing the ability of reinforced concrete (RC) bridges to withstand future seismic demands during their life-cycle can help bridge owners make rational decisions regarding optimal allocation of resources for maintenance, repair, and/or rehabilitation of bridge systems. The accuracy of a reliability assessment can be improved by incorporating information about the current aging and deterioration conditions of a bridge. Nondestructive testing (NDT) can be used to evaluate the actual conditions of a bridge, avoiding the use of deterioration models that bring additional uncertainties in the reliability assessment. This paper develops probabilistic deformation and shear capacity models for RC bridge columns that incorporate information obtained from NDT. The proposed models can be used when the flexural stiffness decays nonuniformly over a column height. The flexural stiffness of a column is estimated based on measured acceleration responses using a system identification method and the damage index method. As an application of the proposed models, a case study assesses the fragility (the conditional probability of attaining or exceeding a specified capacity level) of the column in the Lavic Road Overcrossing for a given deformation or shear demand. This two-span concrete box-girder bridge located in Southern California was subject to the Hector Mine Earthquake in 1999. Pre- and postearthquake estimates of the univariate shear and deformation fragilities and of the bivariate shear-deformation fragility are computed and compared. Both displacement and shear capacities are found to decrease after the earthquake event. Additionally, the results show that the damage due to the Hector Mine Earthquake has a larger impact on the shear capacity than the deformation capacity, leading to a more significant increment in the shear fragility than in the deformation fragility. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Probabilistic capacity models and fragility estimates for reinforced concrete columns incorporating NDT data [texte imprimé] / Huang, Qindan, Auteur ; Gardoni, Paolo, Auteur ; Hurlebaus, Stefan, Auteur . - pp. 1384-1392. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1384-1392 Mots-clés : Bridges  Probability  Nondestructive  tests  Concrete  columns  Reinforced  concrete. Résumé : Knowing the ability of reinforced concrete (RC) bridges to withstand future seismic demands during their life-cycle can help bridge owners make rational decisions regarding optimal allocation of resources for maintenance, repair, and/or rehabilitation of bridge systems. The accuracy of a reliability assessment can be improved by incorporating information about the current aging and deterioration conditions of a bridge. Nondestructive testing (NDT) can be used to evaluate the actual conditions of a bridge, avoiding the use of deterioration models that bring additional uncertainties in the reliability assessment. This paper develops probabilistic deformation and shear capacity models for RC bridge columns that incorporate information obtained from NDT. The proposed models can be used when the flexural stiffness decays nonuniformly over a column height. The flexural stiffness of a column is estimated based on measured acceleration responses using a system identification method and the damage index method. As an application of the proposed models, a case study assesses the fragility (the conditional probability of attaining or exceeding a specified capacity level) of the column in the Lavic Road Overcrossing for a given deformation or shear demand. This two-span concrete box-girder bridge located in Southern California was subject to the Hector Mine Earthquake in 1999. Pre- and postearthquake estimates of the univariate shear and deformation fragilities and of the bivariate shear-deformation fragility are computed and compared. Both displacement and shear capacities are found to decrease after the earthquake event. Additionally, the results show that the damage due to the Hector Mine Earthquake has a larger impact on the shear capacity than the deformation capacity, leading to a more significant increment in the shear fragility than in the deformation fragility. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

Probabilistic capacity models and fragility estimates for steel pedestals used to elevate bridges / Vahid Bisadi in Journal of structural engineering, Vol. 137 N° 12 (Décembre 2011) 

Public ISBD [article]  in Journal of structural engineering > Vol. 137 N° 12 (Décembre 2011) . - pp. 1583-1592 Titre : Probabilistic capacity models and fragility estimates for steel pedestals used to elevate bridges Type de document : texte imprimé Auteurs : Vahid Bisadi, Auteur ; Gardoni, Paolo, Auteur ; Monique Head, Auteur Année de publication : 2012 Article en page(s) : pp. 1583-1592 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Bridges  Capacity  Probability  Estimation Résumé : Using steel pedestals has become an effective method for elevating simply supported bridges in the United States. However, a method is needed to estimate their lateral load capacity and probability of failure subjected to different levels of applied loads. This paper shows the development of probabilistic models for the lateral load capacity of steel pedestals. The capacity models consider the prevailing uncertainties, including statistical uncertainty and model errors due to inaccuracy in the model form or missing variables. The proposed capacity models are used to estimate the conditional failure probability (or fragility) of an example steel pedestal for given sets of lateral and vertical loads. Because of the discontinuity in the limit state function, Monte Carlo simulation is used to estimate the fragility. Results show that for the studied steel pedestal, increasing vertical load decreases the probability of failure subjected to lateral loads. To investigate the effect of different random variables on the results, a sensitivity analysis is also conducted for the example steel pedestal. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i12/p1583_s1?isAuthorized=no [article] Probabilistic capacity models and fragility estimates for steel pedestals used to elevate bridges [texte imprimé] / Vahid Bisadi, Auteur ; Gardoni, Paolo, Auteur ; Monique Head, Auteur . - 2012 . - pp. 1583-1592. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 137 N° 12 (Décembre 2011) . - pp. 1583-1592 Mots-clés : Bridges  Capacity  Probability  Estimation Résumé : Using steel pedestals has become an effective method for elevating simply supported bridges in the United States. However, a method is needed to estimate their lateral load capacity and probability of failure subjected to different levels of applied loads. This paper shows the development of probabilistic models for the lateral load capacity of steel pedestals. The capacity models consider the prevailing uncertainties, including statistical uncertainty and model errors due to inaccuracy in the model form or missing variables. The proposed capacity models are used to estimate the conditional failure probability (or fragility) of an example steel pedestal for given sets of lateral and vertical loads. Because of the discontinuity in the limit state function, Monte Carlo simulation is used to estimate the fragility. Results show that for the studied steel pedestal, increasing vertical load decreases the probability of failure subjected to lateral loads. To investigate the effect of different random variables on the results, a sensitivity analysis is also conducted for the example steel pedestal. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i12/p1583_s1?isAuthorized=no

Probabilistic capacity models for corroding posttensioning strands calibrated using laboratory results / Gardoni, Paolo in Journal of engineering mechanics, Vol. 135 N° 9 (Septembre 2009) 

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Probabilistic models for modulus of elasticity of self-consolidated concrete / Gardoni, Paolo in Journal of engineering mechanics, Vol. 135 N° 4 (Avril 2009) 

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Probabilistic seismic demand models and fragility estimates for reinforced concrete highway bridges with one single-column bent / Qindan Huang in Journal of engineering mechanics, Vol. 136 N° 11 (Novembre 2010) 

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Probability of exceedance estimates for scour depth around bridge piers / Laura C. Bolduc in Journal of geotechnical and geoenvironmental engineering, Vol. 134 N°2 (Fevrier 2008) 

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Seismic response and fragility of deteriorated reinforced concrete bridges / Jessica Simon in Journal of structural engineering, Vol. 136 N° 10 (Octobre 2010) 

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

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