Documents disponibles écrits par cet auteur

Prediction of column axial forces in inverted v-braced seismic steel frames considering brace buckling / ChunHee Cho 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. 1440-1450 Titre : Prediction of column axial forces in inverted v-braced seismic steel frames considering brace buckling Type de document : texte imprimé Auteurs : ChunHee Cho, Auteur ; Cheol-Ho Lee, Auteur ; Jeong-Jae Kim, Auteur Année de publication : 2012 Article en page(s) : pp. 1440-1450 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Brace  buckling  Concentrically  braced  frame  Vertical  unbalanced  force  Column  design  Higher  mode  effects  Pushover  analysis  Seismic Résumé : Brace buckling in inverted-V-braced frames induces the vertical unbalanced force. The columns in the braced bay should be designed, per the capacity design concept, to remain elastic for gravity load actions and additional column axial forces that result from the brace buckling. However, owing to the difficulty in accumulating the buckling-induced column forces from different stories, empirical and often conservative approaches have been used in design practice. In this paper, three combination rules for a rational estimation of the column axial forces are proposed. The idea central to the three methods is to detect the stories with high buckling potential as precisely as possible by using pushover analysis and/or simple demand-to-capacity analysis. The vertical unbalanced forces in the stories detected as high buckling potential are then summed in a linear manner, whereas those otherwise are combined by following the SRSS (square root of sum of squares) rule. The accuracy and design advantage of the three methods is evaluated on the basis of extensive inelastic dynamic analyses. The mode shape-based method (MSBM), which is both simple and accurate, is recommended as the method of choice for practicing engineers among the three proposed. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i12/p1440_s1?isAuthorized=no [article] Prediction of column axial forces in inverted v-braced seismic steel frames considering brace buckling [texte imprimé] / ChunHee Cho, Auteur ; Cheol-Ho Lee, Auteur ; Jeong-Jae Kim, Auteur . - 2012 . - pp. 1440-1450. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 137 N° 12 (Décembre 2011) . - pp. 1440-1450 Mots-clés : Brace  buckling  Concentrically  braced  frame  Vertical  unbalanced  force  Column  design  Higher  mode  effects  Pushover  analysis  Seismic Résumé : Brace buckling in inverted-V-braced frames induces the vertical unbalanced force. The columns in the braced bay should be designed, per the capacity design concept, to remain elastic for gravity load actions and additional column axial forces that result from the brace buckling. However, owing to the difficulty in accumulating the buckling-induced column forces from different stories, empirical and often conservative approaches have been used in design practice. In this paper, three combination rules for a rational estimation of the column axial forces are proposed. The idea central to the three methods is to detect the stories with high buckling potential as precisely as possible by using pushover analysis and/or simple demand-to-capacity analysis. The vertical unbalanced forces in the stories detected as high buckling potential are then summed in a linear manner, whereas those otherwise are combined by following the SRSS (square root of sum of squares) rule. The accuracy and design advantage of the three methods is evaluated on the basis of extensive inelastic dynamic analyses. The mode shape-based method (MSBM), which is both simple and accurate, is recommended as the method of choice for practicing engineers among the three proposed. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i12/p1440_s1?isAuthorized=no

Simulation of the thermal stress in mass concrete using a thermal stress measuring device / Muhammad Nasir Amin in Cement and concrete research, Vol. 39 N° 3 (Mars 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp.154–164 Titre : Simulation of the thermal stress in mass concrete using a thermal stress measuring device Type de document : texte imprimé Auteurs : Muhammad Nasir Amin, Auteur ; Jeong-Jae Kim, Auteur Année de publication : 2009 Article en page(s) : pp.154–164 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Mass  concrete;  Thermal  stress;  Thermal  stress  device;Degree  of  restraint;  Numerical  simulation;  Thermal  expansion  coefficient;  Finite  element  code  DIANA Résumé : An experimental study is conducted to simulate the thermal stresses generated in mass concrete. Accurate prediction of the thermal stresses by analysis is quite difficult particularly at early ages, due to uncertain age-dependent properties of concrete. A series of tests was conducted in which the amount of restraint in a thermal stress device (TSD) was varied. The effect of aging and the amount of restraint on stress development that can occur in realistic structures was evaluated. The influence of the uncertain early-age properties of concrete (i.e., elastic modulus, thermal dilation, autogenous deformation and transitional thermal creep), on the generation of thermal stresses was incorporated using a TSD due to the simultaneous development of temperature and the corresponding stress in a restrained specimen from the very beginning of the process. The effect of various amounts of restraint on the generation of thermal stress was pronounced. Numerical simulations of the thermal stress setup were also performed using the finite element code DIANA to verify and extend the experimental interpretation and to determine the maximum value of restrained stress which would occur under highest level of restraint. Adopting this methodology may simplify the complexity of thermal stress analyses (i.e., more precise 3-D thermal stress analysis can be performed using material properties achieved from 1-D uniaxial tests) due to the difficulty of accurately determining the early-age properties of concrete. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002378 [article] Simulation of the thermal stress in mass concrete using a thermal stress measuring device [texte imprimé] / Muhammad Nasir Amin, Auteur ; Jeong-Jae Kim, Auteur . - 2009 . - pp.154–164. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp.154–164 Mots-clés : Mass  concrete;  Thermal  stress;  Thermal  stress  device;Degree  of  restraint;  Numerical  simulation;  Thermal  expansion  coefficient;  Finite  element  code  DIANA Résumé : An experimental study is conducted to simulate the thermal stresses generated in mass concrete. Accurate prediction of the thermal stresses by analysis is quite difficult particularly at early ages, due to uncertain age-dependent properties of concrete. A series of tests was conducted in which the amount of restraint in a thermal stress device (TSD) was varied. The effect of aging and the amount of restraint on stress development that can occur in realistic structures was evaluated. The influence of the uncertain early-age properties of concrete (i.e., elastic modulus, thermal dilation, autogenous deformation and transitional thermal creep), on the generation of thermal stresses was incorporated using a TSD due to the simultaneous development of temperature and the corresponding stress in a restrained specimen from the very beginning of the process. The effect of various amounts of restraint on the generation of thermal stress was pronounced. Numerical simulations of the thermal stress setup were also performed using the finite element code DIANA to verify and extend the experimental interpretation and to determine the maximum value of restrained stress which would occur under highest level of restraint. Adopting this methodology may simplify the complexity of thermal stress analyses (i.e., more precise 3-D thermal stress analysis can be performed using material properties achieved from 1-D uniaxial tests) due to the difficulty of accurately determining the early-age properties of concrete. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002378