Documents disponibles écrits par cet auteur

Finite-element model updating and probabilistic analysis of timber-concrete composite beams / Zona, Alessandro in Journal of structural engineering, Vol. 138 N° 7 (Juillet 2012) 

Public ISBD [article]  in Journal of structural engineering > Vol. 138 N° 7 (Juillet 2012) . - pp. 899–910 Titre : Finite-element model updating and probabilistic analysis of timber-concrete composite beams Type de document : texte imprimé Auteurs : Zona, Alessandro, Auteur ; Michele Barbato, Auteur ; Massimo Fragiacomo, Auteur Année de publication : 2012 Article en page(s) : pp. 899–910 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Timber  construction  Composite  beams  Finite  element  method  Nonlinear  analysis  Probability  distribution Résumé : Timber-concrete composite beams are an increasingly common design solution for medium-to-long span floors in new buildings. Thus, there is a significant need for accurate models and analysis tools to predict the response and performance of timber-concrete composite beams. In this paper, a nonlinear finite-element (FE) frame model with deformable shear connection is adopted to estimate the short-term structural response of timber-concrete composite beams for which experimental results are available. The FE model is used in conjunction with a probabilistic analysis methodology, which explicitly accounts for the uncertainties in the parameters that describe the constitutive models for timber, concrete, and shear connectors. The objectives of this study are (1) the evaluation of the variability of global and local structural response quantities owing to the uncertainties in the constitutive parameters of timber, concrete, and shear connectors; and (2) the analysis of the correlation between experimental measurements and numerical results based on FE models in which the values of the constitutive parameters are set equal to their experimentally identified mean values and in which the values of the constitutive parameters are optimized through FE model updating, respectively. The results presented in this study show that uncertainties in the constitutive parameters of timber, concrete, and shear connectors have a significant influence on the correlation between the experimental and numerical results. In addition, the optimal values of material parameters obtained using the FE model updating procedure may show substantial variations with respect to the parameters’ mean values as identified in the experimental testing. Prospective developments directed toward design applications and based on the obtained results are also discussed. ISSN : 0733-9445 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29ST.1943-541X.0000509 [article] Finite-element model updating and probabilistic analysis of timber-concrete composite beams [texte imprimé] / Zona, Alessandro, Auteur ; Michele Barbato, Auteur ; Massimo Fragiacomo, Auteur . - 2012 . - pp. 899–910. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 138 N° 7 (Juillet 2012) . - pp. 899–910 Mots-clés : Timber  construction  Composite  beams  Finite  element  method  Nonlinear  analysis  Probability  distribution Résumé : Timber-concrete composite beams are an increasingly common design solution for medium-to-long span floors in new buildings. Thus, there is a significant need for accurate models and analysis tools to predict the response and performance of timber-concrete composite beams. In this paper, a nonlinear finite-element (FE) frame model with deformable shear connection is adopted to estimate the short-term structural response of timber-concrete composite beams for which experimental results are available. The FE model is used in conjunction with a probabilistic analysis methodology, which explicitly accounts for the uncertainties in the parameters that describe the constitutive models for timber, concrete, and shear connectors. The objectives of this study are (1) the evaluation of the variability of global and local structural response quantities owing to the uncertainties in the constitutive parameters of timber, concrete, and shear connectors; and (2) the analysis of the correlation between experimental measurements and numerical results based on FE models in which the values of the constitutive parameters are set equal to their experimentally identified mean values and in which the values of the constitutive parameters are optimized through FE model updating, respectively. The results presented in this study show that uncertainties in the constitutive parameters of timber, concrete, and shear connectors have a significant influence on the correlation between the experimental and numerical results. In addition, the optimal values of material parameters obtained using the FE model updating procedure may show substantial variations with respect to the parameters’ mean values as identified in the experimental testing. Prospective developments directed toward design applications and based on the obtained results are also discussed. ISSN : 0733-9445 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29ST.1943-541X.0000509

Handling of constraints in finite-element response sensitivity analysis / Quan Gu 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. 1427-1438 Titre : Handling of constraints in finite-element response sensitivity analysis Type de document : texte imprimé Auteurs : Quan Gu, Auteur ; Michele Barbato, Auteur ; Conte, Joel P., Auteur Article en page(s) : pp. 1427-1438 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Finite  element  method  Constitutive  models  Constraints  Sensitivity  analysis  Soil-structure  interactions Résumé : In this paper, the direct differentiation method (DDM) for finite-element (FE) response sensitivity analysis is extended to linear and nonlinear FE models with multi-point constraints (MPCs). The analytical developments are provided for three different constraint handling methods, namely: (1) the transformation equation method; (2) the Lagrange multiplier method; and (3) the penalty function method. Two nonlinear benchmark applications are presented: (1) a two-dimensional soil-foundation-structure interaction system and (2) a three-dimensional, one-bay by one-bay, three-story reinforced concrete building with floor slabs modeled as rigid diaphragms, both subjected to seismic excitation. Time histories of response parameters and their sensitivities to material constitutive parameters are computed and discussed, with emphasis on the relative importance of these parameters in affecting the structural response. The DDM-based response sensitivity results are compared with corresponding forward finite difference analysis results, thus validating the formulation presented and its computer implementation. The developments presented in this paper close an important gap between FE response-only analysis and FE response sensitivity analysis through the DDM, extending the latter to applications requiring response sensitivities of FE models with MPCs. These applications include structural optimization, structural reliability analysis, and finite-element model updating. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Handling of constraints in finite-element response sensitivity analysis [texte imprimé] / Quan Gu, Auteur ; Michele Barbato, Auteur ; Conte, Joel P., Auteur . - pp. 1427-1438. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1427-1438 Mots-clés : Finite  element  method  Constitutive  models  Constraints  Sensitivity  analysis  Soil-structure  interactions Résumé : In this paper, the direct differentiation method (DDM) for finite-element (FE) response sensitivity analysis is extended to linear and nonlinear FE models with multi-point constraints (MPCs). The analytical developments are provided for three different constraint handling methods, namely: (1) the transformation equation method; (2) the Lagrange multiplier method; and (3) the penalty function method. Two nonlinear benchmark applications are presented: (1) a two-dimensional soil-foundation-structure interaction system and (2) a three-dimensional, one-bay by one-bay, three-story reinforced concrete building with floor slabs modeled as rigid diaphragms, both subjected to seismic excitation. Time histories of response parameters and their sensitivities to material constitutive parameters are computed and discussed, with emphasis on the relative importance of these parameters in affecting the structural response. The DDM-based response sensitivity results are compared with corresponding forward finite difference analysis results, thus validating the formulation presented and its computer implementation. The developments presented in this paper close an important gap between FE response-only analysis and FE response sensitivity analysis through the DDM, extending the latter to applications requiring response sensitivities of FE models with MPCs. These applications include structural optimization, structural reliability analysis, and finite-element model updating. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

New analytical solution of the first - passage reliability problem for linear oscillators / Sara Ghazizadeh in Journal of engineering mechanics, Vol. 138 N° 6 (Juin 2012) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 138 N° 6 (Juin 2012) . - pp.659-706 Titre : New analytical solution of the first - passage reliability problem for linear oscillators Type de document : texte imprimé Auteurs : Sara Ghazizadeh, Auteur ; Michele Barbato, Auteur ; Enrico Tubaldi, Auteur Année de publication : 2012 Article en page(s) : pp.659-706 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : First-passage  reliability  problem,  Time  variant  analysis,  Structural  reliability  Stochastic  dynamics  Nonstationary  processes Résumé : The classical first-passage reliability problem for linear elastic single-degree-of-freedom (SDOF) oscillators subjected to stationary and nonstationary Gaussian excitations is explored. Several analytical approximations are available in the literature for this problem: the Poisson, classical Vanmarcke, and modified Vanmarcke approximations. These analytical approximations are widely used because of their simplicity and their lower computational cost compared with simulation techniques. However, little is known about their accuracy in estimating the time-variant first-passage failure probability (FPFP) for varying oscillator properties, failure thresholds, and types of loading. In this paper, a new analytical approximation of the FPFP for linear SDOF systems is proposed by modifying the classical Vanmarcke hazard function. This new approximation is verified by comparing its failure probability estimates with the results obtained using existing analytical approximations and the importance sampling using elementary events method for a wide range of oscillator properties, threshold levels, and types of input excitations. It is shown that the newly proposed analytical approximation of the hazard function yields a significantly more accurate estimate of the FPFP compared with the Poisson, classical Vanmarcke, and modified Vanmarcke approximations. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000365 [article] New analytical solution of the first - passage reliability problem for linear oscillators [texte imprimé] / Sara Ghazizadeh, Auteur ; Michele Barbato, Auteur ; Enrico Tubaldi, Auteur . - 2012 . - pp.659-706. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 138 N° 6 (Juin 2012) . - pp.659-706 Mots-clés : First-passage  reliability  problem,  Time  variant  analysis,  Structural  reliability  Stochastic  dynamics  Nonstationary  processes Résumé : The classical first-passage reliability problem for linear elastic single-degree-of-freedom (SDOF) oscillators subjected to stationary and nonstationary Gaussian excitations is explored. Several analytical approximations are available in the literature for this problem: the Poisson, classical Vanmarcke, and modified Vanmarcke approximations. These analytical approximations are widely used because of their simplicity and their lower computational cost compared with simulation techniques. However, little is known about their accuracy in estimating the time-variant first-passage failure probability (FPFP) for varying oscillator properties, failure thresholds, and types of loading. In this paper, a new analytical approximation of the FPFP for linear SDOF systems is proposed by modifying the classical Vanmarcke hazard function. This new approximation is verified by comparing its failure probability estimates with the results obtained using existing analytical approximations and the importance sampling using elementary events method for a wide range of oscillator properties, threshold levels, and types of input excitations. It is shown that the newly proposed analytical approximation of the hazard function yields a significantly more accurate estimate of the FPFP compared with the Poisson, classical Vanmarcke, and modified Vanmarcke approximations. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000365

New multidimensional visualization technique for limit-state surfaces in nonlinear finite-element reliability analysis / Michele Barbato in Journal of engineering mechanics, Vol. 136 N° 11 (Novembre 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 11 (Novembre 2010) . - pp.1390-1400 Titre : New multidimensional visualization technique for limit-state surfaces in nonlinear finite-element reliability analysis Type de document : texte imprimé Auteurs : Michele Barbato, Auteur ; Quan Gu, Auteur ; Joel P. Conte, Auteur Année de publication : 2011 Article en page(s) : pp.1390-1400 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Finite  element  method  Structural  reliability  Limit  states  Imaging  techniques. Résumé : Structural reliability problems involving the use of advanced finite-element models of real-world structures are usually defined by limit-states expressed as functions (referred to as limit-state functions) of basic random variables used to characterize the pertinent sources of uncertainty. These limit-state functions define hyper-surfaces (referred to as limit-state surfaces) in the high-dimensional spaces of the basic random variables. The hyper-surface topology is of paramount interest, particularly in the failure domain regions with highest probability density. In fact, classical asymptotic reliability methods, such as the first- and second-order reliability method (FORM and SORM), are based on geometric approximations of the limit-state surfaces near the so-called design point(s) (DP). This paper presents a new efficient tool, the multidimensional visualization in the principal planes (MVPP) method, to study the topology of high-dimensional nonlinear limit-state surfaces (LSSs) near their DPs. The MVPP method allows the visualization, in particularly meaningful two-dimensional subspaces denoted as principal planes, of actual high-dimensional nonlinear limit-state surfaces that arise in both time-invariant and time-variant (mean out-crossing rate computation) structural reliability problems. The MVPP method provides, at a computational cost comparable with SORM, valuable insight into the suitability of FORM/SORM approximations of the failure probability for various reliability problems. Several application examples are presented to illustrate the developed MVPP methodology and the value of the information provided by visualization of the LSS. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v136/i11/p1390_s1?isAuthorized=no [article] New multidimensional visualization technique for limit-state surfaces in nonlinear finite-element reliability analysis [texte imprimé] / Michele Barbato, Auteur ; Quan Gu, Auteur ; Joel P. Conte, Auteur . - 2011 . - pp.1390-1400. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 11 (Novembre 2010) . - pp.1390-1400 Mots-clés : Finite  element  method  Structural  reliability  Limit  states  Imaging  techniques. Résumé : Structural reliability problems involving the use of advanced finite-element models of real-world structures are usually defined by limit-states expressed as functions (referred to as limit-state functions) of basic random variables used to characterize the pertinent sources of uncertainty. These limit-state functions define hyper-surfaces (referred to as limit-state surfaces) in the high-dimensional spaces of the basic random variables. The hyper-surface topology is of paramount interest, particularly in the failure domain regions with highest probability density. In fact, classical asymptotic reliability methods, such as the first- and second-order reliability method (FORM and SORM), are based on geometric approximations of the limit-state surfaces near the so-called design point(s) (DP). This paper presents a new efficient tool, the multidimensional visualization in the principal planes (MVPP) method, to study the topology of high-dimensional nonlinear limit-state surfaces (LSSs) near their DPs. The MVPP method allows the visualization, in particularly meaningful two-dimensional subspaces denoted as principal planes, of actual high-dimensional nonlinear limit-state surfaces that arise in both time-invariant and time-variant (mean out-crossing rate computation) structural reliability problems. The MVPP method provides, at a computational cost comparable with SORM, valuable insight into the suitability of FORM/SORM approximations of the failure probability for various reliability problems. Several application examples are presented to illustrate the developed MVPP methodology and the value of the information provided by visualization of the LSS. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v136/i11/p1390_s1?isAuthorized=no

Opensees-SNOPT framework for finite-element-based optimization of structural and geotechnical systems / Quan Gu in Journal of structural engineering, Vol. 138 N° 6 (Juin 2012) 

Public ISBD [article]  in Journal of structural engineering > Vol. 138 N° 6 (Juin 2012) . - pp. 822–834 Titre : Opensees-SNOPT framework for finite-element-based optimization of structural and geotechnical systems Type de document : texte imprimé Auteurs : Quan Gu, Auteur ; Michele Barbato, Auteur ; Conte, Joel P., Auteur Année de publication : 2012 Article en page(s) : pp. 822–834 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Finite-element  method  Computational  optimization  Structural  optimization  Structural  reliability  analysis  Finite-element  model  updating  OpenSees  SNOPT Résumé : The finite-element (FE) method is widely recognized as a powerful tool in modeling structural and geotechnical systems and simulating their response to static and dynamic loads. In addition, numerical optimization is commonly used in many engineering applications, such as structural reliability analysis, FE model updating, structural identification, and structural optimization. This paper focuses on the extension of Open System for Earthquake Engineering Simulation (OpenSees, an existing software framework for nonlinear FE analysis) using Sparse Nonlinear Optimization (SNOPT, a state-of-the-art numerical optimization software). The extended OpenSees-SNOPT framework is general and flexible and can be used to solve a wide range of FE-based optimization problems in structural and geotechnical engineering. It has several distinguishing features: (1) advanced capabilities in solving optimization problems involving complex structural/geotechnical engineering systems; (2) versatility in modeling a very wide range of structural and/or geotechnical systems; (3) computational efficiency; (4) flexibility to easily accommodate and benefit from new developments in FE structural modeling and analysis, computational optimization, and probabilistic modeling and analysis; and (5) capabilities of exploring new optimization-based problems and solution methods. The use of this coupled framework is illustrated through three representative application examples, i.e., a FE reliability analysis of a reinforced concrete frame, a FE structural optimization problem of an electrical transmission steel tower, and a FE model updating the problem of a geotechnical system. ISSN : 0733-9445 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29ST.1943-541X.0000511 [article] Opensees-SNOPT framework for finite-element-based optimization of structural and geotechnical systems [texte imprimé] / Quan Gu, Auteur ; Michele Barbato, Auteur ; Conte, Joel P., Auteur . - 2012 . - pp. 822–834. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 138 N° 6 (Juin 2012) . - pp. 822–834 Mots-clés : Finite-element  method  Computational  optimization  Structural  optimization  Structural  reliability  analysis  Finite-element  model  updating  OpenSees  SNOPT Résumé : The finite-element (FE) method is widely recognized as a powerful tool in modeling structural and geotechnical systems and simulating their response to static and dynamic loads. In addition, numerical optimization is commonly used in many engineering applications, such as structural reliability analysis, FE model updating, structural identification, and structural optimization. This paper focuses on the extension of Open System for Earthquake Engineering Simulation (OpenSees, an existing software framework for nonlinear FE analysis) using Sparse Nonlinear Optimization (SNOPT, a state-of-the-art numerical optimization software). The extended OpenSees-SNOPT framework is general and flexible and can be used to solve a wide range of FE-based optimization problems in structural and geotechnical engineering. It has several distinguishing features: (1) advanced capabilities in solving optimization problems involving complex structural/geotechnical engineering systems; (2) versatility in modeling a very wide range of structural and/or geotechnical systems; (3) computational efficiency; (4) flexibility to easily accommodate and benefit from new developments in FE structural modeling and analysis, computational optimization, and probabilistic modeling and analysis; and (5) capabilities of exploring new optimization-based problems and solution methods. The use of this coupled framework is illustrated through three representative application examples, i.e., a FE reliability analysis of a reinforced concrete frame, a FE structural optimization problem of an electrical transmission steel tower, and a FE model updating the problem of a geotechnical system. ISSN : 0733-9445 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29ST.1943-541X.0000511