Documents disponibles écrits par cet auteur

Performance of steel moment connections under a column removal scenario / Sadek, Fahim in Journal of structural engineering, Vol. 139 N° 1 (Janvier 2013) 

Public ISBD [article]  in Journal of structural engineering > Vol. 139 N° 1 (Janvier 2013) . - pp. 108–119 Titre : Performance of steel moment connections under a column removal scenario : II: Analysis Type de document : texte imprimé Auteurs : Sadek, Fahim, Auteur ; Joseph A. Main, Auteur ; H. S. Lew, Auteur Année de publication : 2013 Article en page(s) : pp. 108–119 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Buildings  Connections  FEM  Nonlinear  analysis  Progressive  collapse  Seismic  design  Steel  structures Résumé : This paper presents a computational investigation of the response of steel beam-column assemblies with moment connections under monotonic loading conditions simulating a column removal scenario. Two beam-column assemblies are analyzed, which incorporate (1) welded unreinforced flange bolted web connections, and (2) reduced beam section connections. Detailed models of the assemblies are developed, which use highly refined solid and shell elements to represent nonlinear material behavior and fracture. Reduced models are also developed, which use a much smaller number of beam and spring elements and are intended for use in future studies to assess the vulnerability of complete structural systems to disproportionate collapse. The two modeling approaches are described, and computational results are compared with the results of the full-scale tests described in the companion paper. Good agreement is observed, demonstrating that both the detailed and reduced models are capable of capturing the predominant response characteristics and failure modes of the assemblies, including the development of tensile forces associated with catenary action and the ultimate failure of the moment connections under combined bending and axial stresses. ISSN : 0733-9445 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29ST.1943-541X.0000617 [article] Performance of steel moment connections under a column removal scenario : II: Analysis [texte imprimé] / Sadek, Fahim, Auteur ; Joseph A. Main, Auteur ; H. S. Lew, Auteur . - 2013 . - pp. 108–119. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 139 N° 1 (Janvier 2013) . - pp. 108–119 Mots-clés : Buildings  Connections  FEM  Nonlinear  analysis  Progressive  collapse  Seismic  design  Steel  structures Résumé : This paper presents a computational investigation of the response of steel beam-column assemblies with moment connections under monotonic loading conditions simulating a column removal scenario. Two beam-column assemblies are analyzed, which incorporate (1) welded unreinforced flange bolted web connections, and (2) reduced beam section connections. Detailed models of the assemblies are developed, which use highly refined solid and shell elements to represent nonlinear material behavior and fracture. Reduced models are also developed, which use a much smaller number of beam and spring elements and are intended for use in future studies to assess the vulnerability of complete structural systems to disproportionate collapse. The two modeling approaches are described, and computational results are compared with the results of the full-scale tests described in the companion paper. Good agreement is observed, demonstrating that both the detailed and reduced models are capable of capturing the predominant response characteristics and failure modes of the assemblies, including the development of tensile forces associated with catenary action and the ultimate failure of the moment connections under combined bending and axial stresses. ISSN : 0733-9445 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29ST.1943-541X.0000617

Progressive collapse resistance of steel-concrete composite floors / Alashker, Yasser in Journal of structural engineering, Vol. 136 N° 10 (Octobre 2010) 

Public ISBD [article]  in Journal of structural engineering > Vol. 136 N° 10 (Octobre 2010) . - pp. 1187-1196 Titre : Progressive collapse resistance of steel-concrete composite floors Type de document : texte imprimé Auteurs : Alashker, Yasser, Auteur ; Sherif El-Tawil, Auteur ; Sadek, Fahim, Auteur Année de publication : 2011 Article en page(s) : pp. 1187-1196 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Composite  floor  systems  Robustness  Disproportionate  collapse  Finite-element  analysis  Progressive  collapse  Shear  connections  Shear  tab  Connection Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper discusses the progressive collapse resistance of steel-concrete composite floors in which steel beams are attached to columns through shear tabs. This is a common type of system used for the gravity bay portions of steel buildings. The study is conducted using computational simulation models validated through extensive comparisons to disparate test data. The models are used to investigate key parameters influencing the robustness of generic composite floors subjected to the removal of a center column. In particular, the effects of deck thickness, steel reinforcement, and the numbers of bolts in the shear tab connection on the behavior of the system are studied as a function of the loading scheme. The simulation results show that the majority of collapse resistance comes from the steel deck and that, for the system considered, increasing connection strength by adding more bolts might not be that beneficial in increasing overall collapse strength. The dynamic impact factor, which is widely used to account for dynamic effects within a static design framework, is also computed and the DIF value recommended in existing design guidelines is evaluated. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v136/i10/p1187_s1?isAuthorized=no [article] Progressive collapse resistance of steel-concrete composite floors [texte imprimé] / Alashker, Yasser, Auteur ; Sherif El-Tawil, Auteur ; Sadek, Fahim, Auteur . - 2011 . - pp. 1187-1196. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 136 N° 10 (Octobre 2010) . - pp. 1187-1196 Mots-clés : Composite  floor  systems  Robustness  Disproportionate  collapse  Finite-element  analysis  Progressive  collapse  Shear  connections  Shear  tab  Connection Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper discusses the progressive collapse resistance of steel-concrete composite floors in which steel beams are attached to columns through shear tabs. This is a common type of system used for the gravity bay portions of steel buildings. The study is conducted using computational simulation models validated through extensive comparisons to disparate test data. The models are used to investigate key parameters influencing the robustness of generic composite floors subjected to the removal of a center column. In particular, the effects of deck thickness, steel reinforcement, and the numbers of bolts in the shear tab connection on the behavior of the system are studied as a function of the loading scheme. The simulation results show that the majority of collapse resistance comes from the steel deck and that, for the system considered, increasing connection strength by adding more bolts might not be that beneficial in increasing overall collapse strength. The dynamic impact factor, which is widely used to account for dynamic effects within a static design framework, is also computed and the DIF value recommended in existing design guidelines is evaluated. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v136/i10/p1187_s1?isAuthorized=no

Sampling Errors in the Estimation of Peak Wind-Induced Internal Forces in Low-Rise Structures / Sadek, Fahim in Journal of engineering mechanics, Vol. 130 N°2 (Fevrier 2004)

Public ISBD [article]  in Journal of engineering mechanics > Vol. 130 N°2 (Fevrier 2004) . - 235-239 p. Titre : Sampling Errors in the Estimation of Peak Wind-Induced Internal Forces in Low-Rise Structures Titre original : Erreurs de Prélèvement dans l'Evaluation des Forces Internes Induites par Vent Maximal en Basses Structures d'Elévation Type de document : texte imprimé Auteurs : Sadek, Fahim, Auteur ; Kasperski, Michael, Auteur ; Diniz, Sofia ; Gioffrè, Massimiliano ; Simiu, Emil ; George Deodatis, Editeur scientifique Article en page(s) : 235-239 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Errors  Samples  Buildings  Multistory  Internal  forces  Wind  effects  Stochastic  models  Structural  reliability  Erreurs  Echantillons  Bâtiments  A  plusiers  étages  Forces  internes  Effets  de  vent  Modèles  stochastiques  Fiabilité  structurale Index. décimale : 621.34 Résumé : Peak values in time histories of wind effects may be obtained by using the entire information inherent in the time series of the wind effect, a method entailing the estimation of the probability distribution of the peak through the application of the classical Rice procedure extended for non-Gaussian time histories. We present estimates of the sampling errors inherent in this method. These are needed for structural reliability calculations and for decisions on the requisite length of wind tunnel pressure records, especially for database-assisted design. If based on the analysis of 1-h-long records generated by Monte Carlo simulation, typical sampling errors in the estimation of peaks of time histories corresponding to windstorms of 1-h duration are about 5%. If based on 30- or 20-min records, they are about 1.5 times or twice as large, respectively. Consideration of the sampling errors in reliability calculations entails an estimated increase in the requisite safety margins with respect to wind loading of roughly 2, 3, and 5% if 1-h, 30-min, or 20-min records are used, respectively. Des valeurs maximales dans des histoires de temps des effets de vent peuvent être obtenues en employant l'information entière inhérente à la série chronologique de l'effet de vent, une méthode nécessitant l'évaluation de la distribution de probabilité de la crête par l'application du procédé classique de riz prolongé pour des histoires non gaussiennes de temps. Nous présentons des évaluations des erreurs de prélèvement inhérentes à cette méthode. Ce sont nécessaires pour des calculs structuraux de fiabilité et pour des décisions sur la longueur requise des disques de pression de tunnel de vent, particulièrement pour la conception aidée par base de données. Si basé sur l'analyse des disques 1-h-long produits par la simulation de Monte Carlo, les erreurs de prélèvement typiques dans l'évaluation des crêtes des histoires de temps correspondant au vent donne l' assaut à de la durée 1-h sont environ 5%. Si basé sur 30- ou disques 20-minute, elles sont environ 1.5 fois ou deux fois aussi grand, respectivement. La considération des erreurs de prélèvement dans des calculs de fiabilité nécessite une augmentation estimée des marges de sûreté requises en ce qui concerne le chargement de vent approximativement de 2, de 3, et de 5% si les disques 1-h, 30-minute, ou 20-minute sont employés, respectivement. [article] Sampling Errors in the Estimation of Peak Wind-Induced Internal Forces in Low-Rise Structures = Erreurs de Prélèvement dans l'Evaluation des Forces Internes Induites par Vent Maximal en Basses Structures d'Elévation [texte imprimé] / Sadek, Fahim, Auteur ; Kasperski, Michael, Auteur ; Diniz, Sofia ; Gioffrè, Massimiliano ; Simiu, Emil ; George Deodatis, Editeur scientifique . - 235-239 p. Génie Mécanique Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 130 N°2 (Fevrier 2004) . - 235-239 p. Mots-clés : Errors  Samples  Buildings  Multistory  Internal  forces  Wind  effects  Stochastic  models  Structural  reliability  Erreurs  Echantillons  Bâtiments  A  plusiers  étages  Forces  internes  Effets  de  vent  Modèles  stochastiques  Fiabilité  structurale Index. décimale : 621.34 Résumé : Peak values in time histories of wind effects may be obtained by using the entire information inherent in the time series of the wind effect, a method entailing the estimation of the probability distribution of the peak through the application of the classical Rice procedure extended for non-Gaussian time histories. We present estimates of the sampling errors inherent in this method. These are needed for structural reliability calculations and for decisions on the requisite length of wind tunnel pressure records, especially for database-assisted design. If based on the analysis of 1-h-long records generated by Monte Carlo simulation, typical sampling errors in the estimation of peaks of time histories corresponding to windstorms of 1-h duration are about 5%. If based on 30- or 20-min records, they are about 1.5 times or twice as large, respectively. Consideration of the sampling errors in reliability calculations entails an estimated increase in the requisite safety margins with respect to wind loading of roughly 2, 3, and 5% if 1-h, 30-min, or 20-min records are used, respectively. Des valeurs maximales dans des histoires de temps des effets de vent peuvent être obtenues en employant l'information entière inhérente à la série chronologique de l'effet de vent, une méthode nécessitant l'évaluation de la distribution de probabilité de la crête par l'application du procédé classique de riz prolongé pour des histoires non gaussiennes de temps. Nous présentons des évaluations des erreurs de prélèvement inhérentes à cette méthode. Ce sont nécessaires pour des calculs structuraux de fiabilité et pour des décisions sur la longueur requise des disques de pression de tunnel de vent, particulièrement pour la conception aidée par base de données. Si basé sur l'analyse des disques 1-h-long produits par la simulation de Monte Carlo, les erreurs de prélèvement typiques dans l'évaluation des crêtes des histoires de temps correspondant au vent donne l' assaut à de la durée 1-h sont environ 5%. Si basé sur 30- ou disques 20-minute, elles sont environ 1.5 fois ou deux fois aussi grand, respectivement. La considération des erreurs de prélèvement dans des calculs de fiabilité nécessite une augmentation estimée des marges de sûreté requises en ce qui concerne le chargement de vent approximativement de 2, de 3, et de 5% si les disques 1-h, 30-minute, ou 20-minute sont employés, respectivement.

Testing and analysis of steel and concrete beam-column assemblies under a column removal scenario / Sadek, Fahim in Journal of structural engineering, Vol. 137 N° 9 (Septembre 2011) 

Public ISBD [article]  in Journal of structural engineering > Vol. 137 N° 9 (Septembre 2011) . - pp. 881-892 Titre : Testing and analysis of steel and concrete beam-column assemblies under a column removal scenario Type de document : texte imprimé Auteurs : Sadek, Fahim, Auteur ; Joseph A. Main, Auteur ; H. S. Lew, Auteur Année de publication : 2011 Article en page(s) : pp. 881-892 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Buildings  Concrete  structures  Finite-element  method  Full-scale  tests  Nonlinear  analysis  Progressive  collapse  Seismic  design  Steel  structures Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper presents an experimental and computational assessment of the performance of steel and reinforced concrete beam-column assemblies under monotonic vertical displacement of a center column, simulating a column removal scenario. The assemblies represent portions of structural framing systems designed as intermediate moment frames (IMFs) and special moment frames (SMFs) for Seismic Design Categories C and D, respectively. The steel IMF and SMF assemblies were designed in accordance with ANSI/AISC 341-02 by using prequalified moment connections specified in FEMA 350. The concrete IMF and SMF assemblies were designed and detailed in accordance with ACI 318-02 requirements. Each full-scale assembly comprises two beam spans and three columns, and downward displacements of the center column are imposed until failure. The study provides insight into the behavior and failure modes of the assemblies, including the development of catenary action. Both detailed and reduced finite-element models are developed, which capture the primary response characteristics and failure modes. Analyses with the reduced models can be executed rapidly without loss of accuracy, facilitating implementation in models of entire structural systems. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i9/p881_s1?bypassSSO=1 [article] Testing and analysis of steel and concrete beam-column assemblies under a column removal scenario [texte imprimé] / Sadek, Fahim, Auteur ; Joseph A. Main, Auteur ; H. S. Lew, Auteur . - 2011 . - pp. 881-892. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 137 N° 9 (Septembre 2011) . - pp. 881-892 Mots-clés : Buildings  Concrete  structures  Finite-element  method  Full-scale  tests  Nonlinear  analysis  Progressive  collapse  Seismic  design  Steel  structures Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper presents an experimental and computational assessment of the performance of steel and reinforced concrete beam-column assemblies under monotonic vertical displacement of a center column, simulating a column removal scenario. The assemblies represent portions of structural framing systems designed as intermediate moment frames (IMFs) and special moment frames (SMFs) for Seismic Design Categories C and D, respectively. The steel IMF and SMF assemblies were designed in accordance with ANSI/AISC 341-02 by using prequalified moment connections specified in FEMA 350. The concrete IMF and SMF assemblies were designed and detailed in accordance with ACI 318-02 requirements. Each full-scale assembly comprises two beam spans and three columns, and downward displacements of the center column are imposed until failure. The study provides insight into the behavior and failure modes of the assemblies, including the development of catenary action. Both detailed and reduced finite-element models are developed, which capture the primary response characteristics and failure modes. Analyses with the reduced models can be executed rapidly without loss of accuracy, facilitating implementation in models of entire structural systems. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i9/p881_s1?bypassSSO=1