Documents disponibles écrits par cet auteur

Comparisons of the computed and measured behavior of curved steel I-girders during lifting / Jason C. Stith in Journal of structural engineering, Vol. 138 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of structural engineering > Vol. 138 N° 1 (Janvier 2012) . - pp. 1-10 Titre : Comparisons of the computed and measured behavior of curved steel I-girders during lifting Type de document : texte imprimé Auteurs : Jason C. Stith, Auteur ; Todd A. Helwig, Auteur ; Williamson, Eric B., Auteur Année de publication : 2012 Article en page(s) : pp. 1-10 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Horizontally  curved  girders  Steel  girders  Stability  Field  measurements  Girder  erection  Girder  lifting Résumé : The stability of I-girders during erection can be difficult to assess because of the limited presence of bracing and uncertainty in the support conditions of the girders. The behavior of curved girders during the early stages of construction is complicated because the curved geometry can lead to significant torsion. This paper highlights results from a research study that included both field monitoring and parametric finite-element investigations. Curved I-shaped girders were instrumented and monitored during lifting to provide data to validate finite-element models. Both rotational displacements and stress were measured during the lifting process. In this paper, the writers compare data collected from field tests with results computed from detailed finite-element simulations. A prismatic and a nonprismatic girder (with two different cross sections) were considered in the investigation. The I-girders experienced both rigid body rotation and cross-sectional twist. Additionally, the torsional warping stresses were observed to be of the same order of magnitude as the strong-axis bending stresses. However, it should be noted that the total stresses were well below yielding. The fact that the stresses are low during lifting should not be confused with a noncritical stage in the safety of the girders. Although the applied stresses are low, the stresses necessary to buckle the girder or to cause large deformations are also relatively low because usually no bracing exists and limited restraint is provided to the girders during lifting. The finite-element models were able to capture the measured behavior accurately, providing insight into appropriate assumptions and critical features for modeling curved I-girders during lifting. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v138/i1/p1_s1?isAuthorized=no [article] Comparisons of the computed and measured behavior of curved steel I-girders during lifting [texte imprimé] / Jason C. Stith, Auteur ; Todd A. Helwig, Auteur ; Williamson, Eric B., Auteur . - 2012 . - pp. 1-10. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 138 N° 1 (Janvier 2012) . - pp. 1-10 Mots-clés : Horizontally  curved  girders  Steel  girders  Stability  Field  measurements  Girder  erection  Girder  lifting Résumé : The stability of I-girders during erection can be difficult to assess because of the limited presence of bracing and uncertainty in the support conditions of the girders. The behavior of curved girders during the early stages of construction is complicated because the curved geometry can lead to significant torsion. This paper highlights results from a research study that included both field monitoring and parametric finite-element investigations. Curved I-shaped girders were instrumented and monitored during lifting to provide data to validate finite-element models. Both rotational displacements and stress were measured during the lifting process. In this paper, the writers compare data collected from field tests with results computed from detailed finite-element simulations. A prismatic and a nonprismatic girder (with two different cross sections) were considered in the investigation. The I-girders experienced both rigid body rotation and cross-sectional twist. Additionally, the torsional warping stresses were observed to be of the same order of magnitude as the strong-axis bending stresses. However, it should be noted that the total stresses were well below yielding. The fact that the stresses are low during lifting should not be confused with a noncritical stage in the safety of the girders. Although the applied stresses are low, the stresses necessary to buckle the girder or to cause large deformations are also relatively low because usually no bracing exists and limited restraint is provided to the girders during lifting. The finite-element models were able to capture the measured behavior accurately, providing insight into appropriate assumptions and critical features for modeling curved I-girders during lifting. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v138/i1/p1_s1?isAuthorized=no

Investigation of the damage-dependent response of mooring ropes / Juan Felipe Beltran in Journal of engineering mechanics, Vol. 135 N° 11 (Novembre 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 11 (Novembre 2009) . - pp. 1237-1247 Titre : Investigation of the damage-dependent response of mooring ropes Type de document : texte imprimé Auteurs : Juan Felipe Beltran, Auteur ; Williamson, Eric B., Auteur Article en page(s) : pp. 1237-1247 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Damage  Failures  Mechanical  properties  Models  Mooring. Résumé : The focus of this paper is on the development of an analytical damage model for predicting the deterioration of the mechanical properties of polyester (PET) ropes subjected to static tension loading. Experimental data on small PET ropes are used to estimate the evolution of damage using the effective stress concept and the principle of strain equivalence. The proposed damage model relies on an empirically based cumulative scalar damage function, which is founded on the assumption that the strain range experienced by rope elements is the main source of damage under static tension loading conditions. In this particular study, the evolution of the damage function is represented by both power law and polynomial forms. Based on experimental observations, softening behavior is developed by rope elements after reaching their maximum load-carrying capacities. This softening behavior is captured by the damage function through an asymptotic expansion technique (perturbation method). Comparisons between predicted rope responses and experimental data are provided to illustrate the use of the proposed damage model to estimate PET rope response. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&ONLINE=YES&s [...] [article] Investigation of the damage-dependent response of mooring ropes [texte imprimé] / Juan Felipe Beltran, Auteur ; Williamson, Eric B., Auteur . - pp. 1237-1247. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 11 (Novembre 2009) . - pp. 1237-1247 Mots-clés : Damage  Failures  Mechanical  properties  Models  Mooring. Résumé : The focus of this paper is on the development of an analytical damage model for predicting the deterioration of the mechanical properties of polyester (PET) ropes subjected to static tension loading. Experimental data on small PET ropes are used to estimate the evolution of damage using the effective stress concept and the principle of strain equivalence. The proposed damage model relies on an empirically based cumulative scalar damage function, which is founded on the assumption that the strain range experienced by rope elements is the main source of damage under static tension loading conditions. In this particular study, the evolution of the damage function is represented by both power law and polynomial forms. Based on experimental observations, softening behavior is developed by rope elements after reaching their maximum load-carrying capacities. This softening behavior is captured by the damage function through an asymptotic expansion technique (perturbation method). Comparisons between predicted rope responses and experimental data are provided to illustrate the use of the proposed damage model to estimate PET rope response. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&ONLINE=YES&s [...]

Numerical simulation of damage localization in polyester mooring ropes / Juan Felipe Beltran in Journal of engineering mechanics, Vol. 136 N° 8 (Août 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 8 (Août 2010) . - pp. 945-959 Titre : Numerical simulation of damage localization in polyester mooring ropes Type de document : texte imprimé Auteurs : Juan Felipe Beltran, Auteur ; Williamson, Eric B., Auteur Article en page(s) : pp. 945-959 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Damage  Strain  Localization  Friction  Simulation  Cables. Résumé : This paper presents the derivation of a mechanical model to estimate the effects of damage on the response of ropes. Damage can be represented through a degradation of the properties of individual rope elements, and it can also include the complete rupture of one or more elements. The general assumptions made to estimate the length over which damage propagates along the length of a rope and how this length is considered in modeling damaged rope behavior are explained. Consistent with tests on damaged polyester (PET) mooring ropes, numerical simulations demonstrate the existence of strain localization around the failure region and, due to degradation of rope element properties, damage localization as well. This damage localization causes the premature failure of rope elements, reducing the maximum load capacity and maximum failure strain that a damaged rope is capable of resisting relative to that of an intact rope. The proposed model suggests that some of the variables that affect damaged rope behavior are the degree of damage present at a given cross-section, the location of broken rope elements, and the length over which damage propagates along the rope length. Experimental data are used to validate the model. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Numerical simulation of damage localization in polyester mooring ropes [texte imprimé] / Juan Felipe Beltran, Auteur ; Williamson, Eric B., Auteur . - pp. 945-959. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 8 (Août 2010) . - pp. 945-959 Mots-clés : Damage  Strain  Localization  Friction  Simulation  Cables. Résumé : This paper presents the derivation of a mechanical model to estimate the effects of damage on the response of ropes. Damage can be represented through a degradation of the properties of individual rope elements, and it can also include the complete rupture of one or more elements. The general assumptions made to estimate the length over which damage propagates along the length of a rope and how this length is considered in modeling damaged rope behavior are explained. Consistent with tests on damaged polyester (PET) mooring ropes, numerical simulations demonstrate the existence of strain localization around the failure region and, due to degradation of rope element properties, damage localization as well. This damage localization causes the premature failure of rope elements, reducing the maximum load capacity and maximum failure strain that a damaged rope is capable of resisting relative to that of an intact rope. The proposed model suggests that some of the variables that affect damaged rope behavior are the degree of damage present at a given cross-section, the location of broken rope elements, and the length over which damage propagates along the rope length. Experimental data are used to validate the model. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Response of reinforced concrete bridge columns subjected to blast loads / G. Daniel Williams in Journal of structural engineering, Vol. 137 N° 9 (Septembre 2011) 

Public ISBD [article]  in Journal of structural engineering > Vol. 137 N° 9 (Septembre 2011) . - pp. 903-913 Titre : Response of reinforced concrete bridge columns subjected to blast loads Type de document : texte imprimé Auteurs : G. Daniel Williams, Auteur ; Williamson, Eric B., Auteur Année de publication : 2011 Article en page(s) : pp. 903-913 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Blast  loads  Bridges  Computational  modeling  Terrorism Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The vast majority of past research on blast-resistant structural design focuses on buildings, with limited attention directed specifically towards bridges. Although many of the same principles apply, bridges pose unique challenges that are not often encountered when designing buildings for blast resistance. Specifically, establishing standoff with bridges is difficult because they are intended to provide open access to the traveling public, and structural components are directly loaded rather than having loads transferred to them through a facade system. Thus, relative to buildings, bridge components may be exposed to large blast threats that can be in close proximity to the potential target. To address these unique challenges, experimental and computational research was carried out, through support from the National Cooperative Highway Research Program (NCHRP), to understand the behavior of blast-loaded concrete bridge members. Although spalling of concrete cover off the back of reinforced concrete walls subjected to blast loads is a well-understood phenomenon, specimens experimentally tested for the current research exhibited spalling of side-cover concrete, which previously has not been reported in the research literature. Using detailed finite-element models, this paper explains the cross-sectional response mechanisms that cause spalling of side-cover concrete in blast-loaded slender reinforced concrete members by numerically reproducing the behavior observed during the experimental testing program. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i9/p903_s1?bypassSSO=1 [article] Response of reinforced concrete bridge columns subjected to blast loads [texte imprimé] / G. Daniel Williams, Auteur ; Williamson, Eric B., Auteur . - 2011 . - pp. 903-913. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 137 N° 9 (Septembre 2011) . - pp. 903-913 Mots-clés : Blast  loads  Bridges  Computational  modeling  Terrorism Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The vast majority of past research on blast-resistant structural design focuses on buildings, with limited attention directed specifically towards bridges. Although many of the same principles apply, bridges pose unique challenges that are not often encountered when designing buildings for blast resistance. Specifically, establishing standoff with bridges is difficult because they are intended to provide open access to the traveling public, and structural components are directly loaded rather than having loads transferred to them through a facade system. Thus, relative to buildings, bridge components may be exposed to large blast threats that can be in close proximity to the potential target. To address these unique challenges, experimental and computational research was carried out, through support from the National Cooperative Highway Research Program (NCHRP), to understand the behavior of blast-loaded concrete bridge members. Although spalling of concrete cover off the back of reinforced concrete walls subjected to blast loads is a well-understood phenomenon, specimens experimentally tested for the current research exhibited spalling of side-cover concrete, which previously has not been reported in the research literature. Using detailed finite-element models, this paper explains the cross-sectional response mechanisms that cause spalling of side-cover concrete in blast-loaded slender reinforced concrete members by numerically reproducing the behavior observed during the experimental testing program. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i9/p903_s1?bypassSSO=1