Documents disponibles écrits par cet auteur

Improved estimation of long - term relaxation function from compliance function of aging concrete / Zdenek P. Bazant in Journal of engineering mechanics, Vol. 139 N° 2 (Février 2013) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 139 N° 2 (Février 2013) . - pp.146–152. Titre : Improved estimation of long - term relaxation function from compliance function of aging concrete Type de document : texte imprimé Auteurs : Zdenek P. Bazant, Auteur ; Mija H. Hubler, Auteur ; Milan Jirasek, Auteur Année de publication : 2013 Article en page(s) : pp.146–152. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Creep  Concrete  Stress  relaxation  Aging  Creep  analysis  of  structures Résumé : Based on asymptotic considerations, this paper develops an improved approximate formula for estimating the relaxation function from the given compliance function of concrete, which is considered as aging, linearly viscoelastic material. Compared with the formula developed in 1979 by Bažant and Kim, the new formula prevents any violation of the thermodynamic requirement of nonnegativeness of the relaxation function. It is significantly more accurate for long-time relaxation of concrete loaded at a young age, and, for this reason, it is particularly useful for compliance functions that correctly describe multidecade creep, which is the case for model B3 compliance function (a 1995 international RILEM recommendation) and not, for example, for the compliance functions of the American, European, Japanese, and Canadian standard recommendations, for which the benefit is smaller. The main application of the new formula is to evaluate the aging coefficient of the age-adjusted effective modulus method (AAEM) from the compliance function specified by the standard recommendation. The AAEM, developed in 1972 at Northwestern University and embodied in most standard design recommendations including those of the American Concrete Institute (ACI) and the Fédération internationale du béton (fib), provides an approximate estimate of the creep effects in structures according to the principle of superposition, which itself is a simplification neglecting nonlinear and diffusion effects. ISSN : 0733-9399 En ligne : //ascelibrary.org/doi/abs/10.1061/(ASCE)EM.1943-7889.0000339 [article] Improved estimation of long - term relaxation function from compliance function of aging concrete [texte imprimé] / Zdenek P. Bazant, Auteur ; Mija H. Hubler, Auteur ; Milan Jirasek, Auteur . - 2013 . - pp.146–152. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 139 N° 2 (Février 2013) . - pp.146–152. Mots-clés : Creep  Concrete  Stress  relaxation  Aging  Creep  analysis  of  structures Résumé : Based on asymptotic considerations, this paper develops an improved approximate formula for estimating the relaxation function from the given compliance function of concrete, which is considered as aging, linearly viscoelastic material. Compared with the formula developed in 1979 by Bažant and Kim, the new formula prevents any violation of the thermodynamic requirement of nonnegativeness of the relaxation function. It is significantly more accurate for long-time relaxation of concrete loaded at a young age, and, for this reason, it is particularly useful for compliance functions that correctly describe multidecade creep, which is the case for model B3 compliance function (a 1995 international RILEM recommendation) and not, for example, for the compliance functions of the American, European, Japanese, and Canadian standard recommendations, for which the benefit is smaller. The main application of the new formula is to evaluate the aging coefficient of the age-adjusted effective modulus method (AAEM) from the compliance function specified by the standard recommendation. The AAEM, developed in 1972 at Northwestern University and embodied in most standard design recommendations including those of the American Concrete Institute (ACI) and the Fédération internationale du béton (fib), provides an approximate estimate of the creep effects in structures according to the principle of superposition, which itself is a simplification neglecting nonlinear and diffusion effects. ISSN : 0733-9399 En ligne : //ascelibrary.org/doi/abs/10.1061/(ASCE)EM.1943-7889.0000339