Documents disponibles écrits par cet auteur

Characterization of elastic and time-dependent deformations in high performance lightweight concrete by image analysis / Mauricio Lopez in Cement and concrete research, Vol. 39 N° 7 (Juillet 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 610–619 Titre : Characterization of elastic and time-dependent deformations in high performance lightweight concrete by image analysis Type de document : texte imprimé Auteurs : Mauricio Lopez, Auteur ; Lawrence F. Kahn, Auteur ; Kimberly E. Kurtis, Auteur Année de publication : 2009 Article en page(s) : pp. 610–619 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Aggregate;  Cement  paste;  Creep;  Interfacial  transition  zone;  Shrinkage Résumé : Image analysis and strain mapping were used to examine the nature of elastic, creep and shrinkage strains in high performance lightweight concrete (HPLC). The strain maps showed non-uniform deformations related to microstructural features. Both average strain and non-uniformity increased with time under testing. Paste-rich regions exhibited higher creep plus shrinkage than the lightweight aggregate (LWA) particles examined herein; it is suggested that LWA could have a role in reducing deformations of the paste. Compared to normal weight high performance concrete (HPC), the paste and LWA in the HPLC exhibited more gradual spatial differences in elastic deformations, creep and shrinkage. It is proposed that this difference results from the lower stiffness of the LWA compared to granite used in the HPC. The results indicate that improvement in elastic property matching between the lightweight aggregate and high performance paste reduces stress concentrations at the aggregate/paste interface and contributes to reductions in deformations of HPLC compared to HPC. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000763 [article] Characterization of elastic and time-dependent deformations in high performance lightweight concrete by image analysis [texte imprimé] / Mauricio Lopez, Auteur ; Lawrence F. Kahn, Auteur ; Kimberly E. Kurtis, Auteur . - 2009 . - pp. 610–619. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 610–619 Mots-clés : Aggregate;  Cement  paste;  Creep;  Interfacial  transition  zone;  Shrinkage Résumé : Image analysis and strain mapping were used to examine the nature of elastic, creep and shrinkage strains in high performance lightweight concrete (HPLC). The strain maps showed non-uniform deformations related to microstructural features. Both average strain and non-uniformity increased with time under testing. Paste-rich regions exhibited higher creep plus shrinkage than the lightweight aggregate (LWA) particles examined herein; it is suggested that LWA could have a role in reducing deformations of the paste. Compared to normal weight high performance concrete (HPC), the paste and LWA in the HPLC exhibited more gradual spatial differences in elastic deformations, creep and shrinkage. It is proposed that this difference results from the lower stiffness of the LWA compared to granite used in the HPC. The results indicate that improvement in elastic property matching between the lightweight aggregate and high performance paste reduces stress concentrations at the aggregate/paste interface and contributes to reductions in deformations of HPLC compared to HPC. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000763

Lateral-torsional buckling of structural concrete beams / Jonathan B. Hurff in Journal of structural engineering, Vol. 138 N° 9 (Septembre 2012) 

Public ISBD [article]  in Journal of structural engineering > Vol. 138 N° 9 (Septembre 2012) . - pp. 1138–1148. Titre : Lateral-torsional buckling of structural concrete beams : Experimental and analytical study Type de document : texte imprimé Auteurs : Jonathan B. Hurff, Auteur ; Lawrence F. Kahn, Auteur Année de publication : 2012 Article en page(s) : pp. 1138–1148. Note générale : Génie civil Langues : Anglais (eng) Mots-clés : Buckling  Concrete  beams  Experimentation  Lateral  stability  Prestressed  concrete  Structural  stability Résumé : Precast structural concrete beams have become longer and more slender, increasing the likelihood of a stability failure. Although there are methods to determine the lateral-torsional buckling load for reinforced and prestressed concrete beams, there has been no conformity as to which is the more accurate method, nor do they account for initial imperfections. Six slender, rectangular pretensioned concrete beams were tested and showed that the lateral-torsional stability behavior was similar to that of reinforced concrete beams except for (1) changes in material properties owing to a different stress state and (2) the effects of prestressing on the cracking behavior of the cross section. The stability behavior proved to be sensitive to initial imperfections; therefore, both a geometric nonlinear stability analysis and a simplified equation were developed. The predictive methods were compared with the current and past results, and the analytical methods showed good correlation with all structural concrete experimental results. The results indicate that prestressed concrete beams are susceptible to lateral-torsional buckling and the initial imperfections serve to reduce the buckling load owing to nonlinear geometric behavior and a nonrectangular compression zone. ISSN : 0733-9445 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29ST.1943-541X.0000542 [article] Lateral-torsional buckling of structural concrete beams : Experimental and analytical study [texte imprimé] / Jonathan B. Hurff, Auteur ; Lawrence F. Kahn, Auteur . - 2012 . - pp. 1138–1148. Génie civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 138 N° 9 (Septembre 2012) . - pp. 1138–1148. Mots-clés : Buckling  Concrete  beams  Experimentation  Lateral  stability  Prestressed  concrete  Structural  stability Résumé : Precast structural concrete beams have become longer and more slender, increasing the likelihood of a stability failure. Although there are methods to determine the lateral-torsional buckling load for reinforced and prestressed concrete beams, there has been no conformity as to which is the more accurate method, nor do they account for initial imperfections. Six slender, rectangular pretensioned concrete beams were tested and showed that the lateral-torsional stability behavior was similar to that of reinforced concrete beams except for (1) changes in material properties owing to a different stress state and (2) the effects of prestressing on the cracking behavior of the cross section. The stability behavior proved to be sensitive to initial imperfections; therefore, both a geometric nonlinear stability analysis and a simplified equation were developed. The predictive methods were compared with the current and past results, and the analytical methods showed good correlation with all structural concrete experimental results. The results indicate that prestressed concrete beams are susceptible to lateral-torsional buckling and the initial imperfections serve to reduce the buckling load owing to nonlinear geometric behavior and a nonrectangular compression zone. ISSN : 0733-9445 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29ST.1943-541X.0000542