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Analytical and numerical modeling of prestressed continuous steel-concrete composite beams / Jianguo Nie 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. 1405-1418 Titre : Analytical and numerical modeling of prestressed continuous steel-concrete composite beams Type de document : texte imprimé Auteurs : Jianguo Nie, Auteur ; Muxuan Tao, Auteur ; C. S. Cai, Auteur Année de publication : 2012 Article en page(s) : pp. 1405-1418 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Prestressed  concrete  Composite  beam  Continuous  beam  Loading  capacity  Crack  load  Yield  load  Ultimate  load  Finite  element  analysis  Nonlinear  Whole  process Résumé : A loading capacity analysis is conducted for prestressed continuous steel-concrete composite beams. On the basis of the basic theoretical framework of the solution of externally unbonded prestressed structures, formulas for calculating the three characteristic loads (crack, yield, and ultimate loads) of two-span prestressed continuous composite beams under symmetric concentrated loads are proposed and extended to general cases. The variation of tendon force is considered and the adopted limit equilibrium approach only requires the development of equilibrium equations, which avoids the solution of cumbersome simultaneous deformation compatibility equations. Furthermore, an elaborate finite element model is presented for simulating the nonlinear behavior of prestressed continuous composite beams by using the commercial finite element package. The numerical model considering both the material and geometric nonlinearities can fully reflect the complex behaviors of prestressed continuous composite beams during the whole loading process. The comparisons among the analytical, numerical, and experimental results demonstrate that the analytical method provides a convenient and reliable tool for a routine design practice and the finite element model provides an excellent numerical simulation for the nonlinear behavior of prestressed continuous composite beams. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i12/p1405_s1?isAuthorized=no [article] Analytical and numerical modeling of prestressed continuous steel-concrete composite beams [texte imprimé] / Jianguo Nie, Auteur ; Muxuan Tao, Auteur ; C. S. Cai, Auteur . - 2012 . - pp. 1405-1418. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 137 N° 12 (Décembre 2011) . - pp. 1405-1418 Mots-clés : Prestressed  concrete  Composite  beam  Continuous  beam  Loading  capacity  Crack  load  Yield  load  Ultimate  load  Finite  element  analysis  Nonlinear  Whole  process Résumé : A loading capacity analysis is conducted for prestressed continuous steel-concrete composite beams. On the basis of the basic theoretical framework of the solution of externally unbonded prestressed structures, formulas for calculating the three characteristic loads (crack, yield, and ultimate loads) of two-span prestressed continuous composite beams under symmetric concentrated loads are proposed and extended to general cases. The variation of tendon force is considered and the adopted limit equilibrium approach only requires the development of equilibrium equations, which avoids the solution of cumbersome simultaneous deformation compatibility equations. Furthermore, an elaborate finite element model is presented for simulating the nonlinear behavior of prestressed continuous composite beams by using the commercial finite element package. The numerical model considering both the material and geometric nonlinearities can fully reflect the complex behaviors of prestressed continuous composite beams during the whole loading process. The comparisons among the analytical, numerical, and experimental results demonstrate that the analytical method provides a convenient and reliable tool for a routine design practice and the finite element model provides an excellent numerical simulation for the nonlinear behavior of prestressed continuous composite beams. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i12/p1405_s1?isAuthorized=no

Evaluating wind loads on bridge decks using velocity fields / W. Zhang in Journal of engineering mechanics, Vol. 139 N° 3 (Mars 2013) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 139 N° 3 (Mars 2013) . - pp.339–346. Titre : Evaluating wind loads on bridge decks using velocity fields Type de document : texte imprimé Auteurs : W. Zhang, Auteur ; Y. J. Ge, Auteur ; C. S. Cai, Auteur Année de publication : 2013 Article en page(s) : pp.339–346. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Wind  force  Wind-velocity  fields  Square  cylinder  Twin-box  girder  Particle  image  velocimetry  Computational  fluid  dynamics Résumé : The wind loads including forces and moments on bridge decks are evaluated in the current study using the velocity fields and their derivatives. Based on the conservation of momentum and momentum moment, the integral over the control volume is converted to the surface integral over the boundary of the control volume using the divergence theorem. The wind forces and moments can be calculated based on the obtained velocity fields and their derivatives around bridge decks, and the pressure terms in the equations are canceled out. Velocity fields are obtained from computational fluid dynamics (CFD) simulations and particle image velocimetry (PIV) wind tunnel experiments. Results from different turbulence models are compared with each other and wind tunnel experimental results in the literature. The calculated wind loads from numerical integrations of velocity fields from PIV experiments or CFD numerical simulations are compared with the results from a direct integration of the CFD-simulated surface pressure and the results from force-balance measurements in the wind tunnel. The results from several cases with different sizes of control volumes and space resolutions for both the square cylinder section and the twin-box girder section are discussed. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000504 [article] Evaluating wind loads on bridge decks using velocity fields [texte imprimé] / W. Zhang, Auteur ; Y. J. Ge, Auteur ; C. S. Cai, Auteur . - 2013 . - pp.339–346. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 139 N° 3 (Mars 2013) . - pp.339–346. Mots-clés : Wind  force  Wind-velocity  fields  Square  cylinder  Twin-box  girder  Particle  image  velocimetry  Computational  fluid  dynamics Résumé : The wind loads including forces and moments on bridge decks are evaluated in the current study using the velocity fields and their derivatives. Based on the conservation of momentum and momentum moment, the integral over the control volume is converted to the surface integral over the boundary of the control volume using the divergence theorem. The wind forces and moments can be calculated based on the obtained velocity fields and their derivatives around bridge decks, and the pressure terms in the equations are canceled out. Velocity fields are obtained from computational fluid dynamics (CFD) simulations and particle image velocimetry (PIV) wind tunnel experiments. Results from different turbulence models are compared with each other and wind tunnel experimental results in the literature. The calculated wind loads from numerical integrations of velocity fields from PIV experiments or CFD numerical simulations are compared with the results from a direct integration of the CFD-simulated surface pressure and the results from force-balance measurements in the wind tunnel. The results from several cases with different sizes of control volumes and space resolutions for both the square cylinder section and the twin-box girder section are discussed. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000504

Experimental research on fatigue behavior of RC beams strengthened with steel plate-concrete composite technique / Jianguo Nie in Journal of structural engineering, Vol. 137 N° 7 (Juillet 2011) 

Public ISBD [article]  in Journal of structural engineering > Vol. 137 N° 7 (Juillet 2011) . - pp. 772-781 Titre : Experimental research on fatigue behavior of RC beams strengthened with steel plate-concrete composite technique Type de document : texte imprimé Auteurs : Jianguo Nie, Auteur ; Yuhang Wang, Auteur ; C. S. Cai, Auteur Année de publication : 2011 Article en page(s) : pp. 772-781 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Steel  plate-concrete  composite  technique  Strengthening  Strengthening  under  sustained  load  Load  bearing  capacity  Fatigue Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Based on fatigue experiments on eight reinforced concrete (RC) beams strengthened with the steel plate-concrete composite (SPCC) technique, the fatigue life and development trend of stiffness and strain of specimens under a constant amplitude fatigue loading were studied. The experimental results showed that the fatigue failure mode of the SPCC strengthened beams was the fatigue failure of the steel plate. The initial fatigue crack in the steel plate appeared near the weld toe of studs and then expanded through the plate. Unlike regular RC beams, the fatigue failure mode of the tested specimens was ductile. The amplitude of stress in the steel plate had the most important influence on the fatigue behavior of RC beams strengthened with the SPCC technique. The level and amplitude of stress in the steel plate should be strictly controlled in practical design, and therefore, the high-strength steel and thin steel plate were not suitable for RC beams strengthened with the SPCC technique. The prestress in the steel plate could improve the fatigue life of RC beams strengthened with the SPCC technique. The S-N curve of the tension steel plate, welded with studs specified in the British code of practice for bridge design, BS5400, was conservative for the design of steel plate in RC beams strengthened with the SPCC technique. Calculation models were presented of the residual static capacity and stiffness of RC beams strengthened with the SPCC technique after fatigue failure. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i7/p772_s1?isAuthorized=no [article] Experimental research on fatigue behavior of RC beams strengthened with steel plate-concrete composite technique [texte imprimé] / Jianguo Nie, Auteur ; Yuhang Wang, Auteur ; C. S. Cai, Auteur . - 2011 . - pp. 772-781. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 137 N° 7 (Juillet 2011) . - pp. 772-781 Mots-clés : Steel  plate-concrete  composite  technique  Strengthening  Strengthening  under  sustained  load  Load  bearing  capacity  Fatigue Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Based on fatigue experiments on eight reinforced concrete (RC) beams strengthened with the steel plate-concrete composite (SPCC) technique, the fatigue life and development trend of stiffness and strain of specimens under a constant amplitude fatigue loading were studied. The experimental results showed that the fatigue failure mode of the SPCC strengthened beams was the fatigue failure of the steel plate. The initial fatigue crack in the steel plate appeared near the weld toe of studs and then expanded through the plate. Unlike regular RC beams, the fatigue failure mode of the tested specimens was ductile. The amplitude of stress in the steel plate had the most important influence on the fatigue behavior of RC beams strengthened with the SPCC technique. The level and amplitude of stress in the steel plate should be strictly controlled in practical design, and therefore, the high-strength steel and thin steel plate were not suitable for RC beams strengthened with the SPCC technique. The prestress in the steel plate could improve the fatigue life of RC beams strengthened with the SPCC technique. The S-N curve of the tension steel plate, welded with studs specified in the British code of practice for bridge design, BS5400, was conservative for the design of steel plate in RC beams strengthened with the SPCC technique. Calculation models were presented of the residual static capacity and stiffness of RC beams strengthened with the SPCC technique after fatigue failure. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i7/p772_s1?isAuthorized=no

Wind - induced internal pressures of buildings with multiple openings / F. Pan in Journal of engineering mechanics, Vol. 139 N° 3 (Mars 2013) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 139 N° 3 (Mars 2013) . - pp.376–385. Titre : Wind - induced internal pressures of buildings with multiple openings Type de document : texte imprimé Auteurs : F. Pan, Auteur ; C. S. Cai, Auteur ; W. Zhang, Auteur Année de publication : 2013 Article en page(s) : pp.376–385. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Internal  pressure  Wind  loads  Buildings  Low  rise  Aerodynamics,  Residential Résumé : Based on previous studies, it has been determined that internal pressures can contribute as much (or more) as the external pressures to the net pressures occasioned for low-rise buildings with a single dominant opening. However, the role of internal pressures, as experienced for cases with realistic geometry and multiple openings, is rarely investigated. As is known, low-rise buildings are susceptible to multiple-opening failures during strong windstorms, and the resulting changes in internal pressures are critical measures for tracking how the failure progresses from a localized level to a catastrophic level. Using the Wind Tunnel Laboratory located at Louisiana State University, by testing a typical 5:12 gable-roof residential-building model with 17 openings, a full picture of the internal pressure changes experienced during progressive failure of multiple openings is obtained. The results indicated that (1) mean internal pressure coefficients estimated by two currently available, public hurricane-loss models were closer to the minimum internal pressure coefficient measurements than the mean internal pressure coefficient measurements at each stage of the multiple-opening failure; (2) ASCE guidelines underestimate the internal pressure for both partially enclosed and enclosed building types; and (3) Helmholtz resonance occurred near the theoretical resonance frequencies for two single opening cases for the current model with high damping. Based on these results, the flow resonance, dependent on the building geometry and the opening layout, should be considered to predict the potential wind-induced damage for low-rise buildings, and this is what is explored in this paper. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000464 [article] Wind - induced internal pressures of buildings with multiple openings [texte imprimé] / F. Pan, Auteur ; C. S. Cai, Auteur ; W. Zhang, Auteur . - 2013 . - pp.376–385. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 139 N° 3 (Mars 2013) . - pp.376–385. Mots-clés : Internal  pressure  Wind  loads  Buildings  Low  rise  Aerodynamics,  Residential Résumé : Based on previous studies, it has been determined that internal pressures can contribute as much (or more) as the external pressures to the net pressures occasioned for low-rise buildings with a single dominant opening. However, the role of internal pressures, as experienced for cases with realistic geometry and multiple openings, is rarely investigated. As is known, low-rise buildings are susceptible to multiple-opening failures during strong windstorms, and the resulting changes in internal pressures are critical measures for tracking how the failure progresses from a localized level to a catastrophic level. Using the Wind Tunnel Laboratory located at Louisiana State University, by testing a typical 5:12 gable-roof residential-building model with 17 openings, a full picture of the internal pressure changes experienced during progressive failure of multiple openings is obtained. The results indicated that (1) mean internal pressure coefficients estimated by two currently available, public hurricane-loss models were closer to the minimum internal pressure coefficient measurements than the mean internal pressure coefficient measurements at each stage of the multiple-opening failure; (2) ASCE guidelines underestimate the internal pressure for both partially enclosed and enclosed building types; and (3) Helmholtz resonance occurred near the theoretical resonance frequencies for two single opening cases for the current model with high damping. Based on these results, the flow resonance, dependent on the building geometry and the opening layout, should be considered to predict the potential wind-induced damage for low-rise buildings, and this is what is explored in this paper. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000464