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Air-blast effects on structural shapes of finite width / Graeme J. Ballantyne in Journal of structural engineering, Vol. 136 N° 2 (Fevrier 2010) 

Public ISBD [article]  in Journal of structural engineering > Vol. 136 N° 2 (Fevrier 2010) . - pp. 152-159 Titre : Air-blast effects on structural shapes of finite width Type de document : texte imprimé Auteurs : Graeme J. Ballantyne, Auteur ; Andrew S. Whittaker, Auteur ; Gary F. Dargush, Auteur Année de publication : 2011 Article en page(s) : pp. 152-159 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Blast  loading  Clearing  Impulsive  loading  Extreme  loading Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : In blast engineering, many designs begin with simplified hand procedures with the loading parameters determined based upon a reflective surface of infinite size. Individual structural members such as columns have finite widths and should be considered as finite surfaces for blast loading calculations. A study was performed to investigate the effect of finite flange width on blast loadings on structural components. The diffraction of a blast wave around the leading edges of the cross section and the propagation of rarefaction waves from the leading edges to the column centerline leads to a more rapid reduction in reflected pressure than that of an infinite surface: a process that is widely known as clearing. A series of analyses were performed using the computational fluid dynamics code Air3d. Peak reflected pressures are not changed by the “finiteness” of the section, although the reflected impulse can be substantially reduced by clearing. For a given charge mass, held constant for a range of stand-off distances, R, impulse is approximately proportional to 1/R when considering an infinite surface. If clearing is considered, the reflected impulse is still proportional to 1/R, but can be 50% lower than the value computed for an infinite surface, which has significant implications for blast resistant design of structural components. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v136/i2/p152_s1?isAuthorized=no [article] Air-blast effects on structural shapes of finite width [texte imprimé] / Graeme J. Ballantyne, Auteur ; Andrew S. Whittaker, Auteur ; Gary F. Dargush, Auteur . - 2011 . - pp. 152-159. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 136 N° 2 (Fevrier 2010) . - pp. 152-159 Mots-clés : Blast  loading  Clearing  Impulsive  loading  Extreme  loading Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : In blast engineering, many designs begin with simplified hand procedures with the loading parameters determined based upon a reflective surface of infinite size. Individual structural members such as columns have finite widths and should be considered as finite surfaces for blast loading calculations. A study was performed to investigate the effect of finite flange width on blast loadings on structural components. The diffraction of a blast wave around the leading edges of the cross section and the propagation of rarefaction waves from the leading edges to the column centerline leads to a more rapid reduction in reflected pressure than that of an infinite surface: a process that is widely known as clearing. A series of analyses were performed using the computational fluid dynamics code Air3d. Peak reflected pressures are not changed by the “finiteness” of the section, although the reflected impulse can be substantially reduced by clearing. For a given charge mass, held constant for a range of stand-off distances, R, impulse is approximately proportional to 1/R when considering an infinite surface. If clearing is considered, the reflected impulse is still proportional to 1/R, but can be 50% lower than the value computed for an infinite surface, which has significant implications for blast resistant design of structural components. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v136/i2/p152_s1?isAuthorized=no

Mixed lagrangian formulation for linear thermoelastic response of structures / Georgios Apostolakis in Journal of engineering mechanics, Vol. 138 N° 5 (Mai 2012) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 138 N° 5 (Mai 2012) . - pp.508-518 Titre : Mixed lagrangian formulation for linear thermoelastic response of structures Type de document : texte imprimé Auteurs : Georgios Apostolakis, Auteur ; Gary F. Dargush, Auteur Année de publication : 2012 Article en page(s) : pp.508-518 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Thermoelasticity,  Variational  methods,  Mixed  Lagrangian  formulation  Hamilton’s  principle,  Discrete  variational  calculus  Mixed  methods  Flexibility  methods  Symplectic  algorithms Résumé : Although a complete unified theory for elasticity, plasticity, and damage does not yet exist, an approach on the basis of thermomechanical principles may be able to serve as the foundation for such a theory. With this in mind, as a first step, a mixed formulation is developed for fully coupled, spatially discretized linear thermoelasticity under the Lagrangian formalism by using Hamilton’s principle. A variational integration scheme is then proposed for the temporal discretization of the resulting Euler-Lagrange equations. With this discrete numerical time-step solution, it becomes possible, for proper choices of state variables, to restate the problem in the form of an optimization. Ultimately, this allows the formulation of a principle of minimum generalized complementary potential energy for the discrete-time thermoelastic system. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000346 [article] Mixed lagrangian formulation for linear thermoelastic response of structures [texte imprimé] / Georgios Apostolakis, Auteur ; Gary F. Dargush, Auteur . - 2012 . - pp.508-518. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 138 N° 5 (Mai 2012) . - pp.508-518 Mots-clés : Thermoelasticity,  Variational  methods,  Mixed  Lagrangian  formulation  Hamilton’s  principle,  Discrete  variational  calculus  Mixed  methods  Flexibility  methods  Symplectic  algorithms Résumé : Although a complete unified theory for elasticity, plasticity, and damage does not yet exist, an approach on the basis of thermomechanical principles may be able to serve as the foundation for such a theory. With this in mind, as a first step, a mixed formulation is developed for fully coupled, spatially discretized linear thermoelasticity under the Lagrangian formalism by using Hamilton’s principle. A variational integration scheme is then proposed for the temporal discretization of the resulting Euler-Lagrange equations. With this discrete numerical time-step solution, it becomes possible, for proper choices of state variables, to restate the problem in the form of an optimization. Ultimately, this allows the formulation of a principle of minimum generalized complementary potential energy for the discrete-time thermoelastic system. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000346