Dépouillements

Eliminating temperature effect in vibration - based structural damage detection / H. F. Zhou in Journal of engineering mechanics, Vol. 137 N° 12 (Decembre 2011) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.785-796 Titre : Eliminating temperature effect in vibration - based structural damage detection Type de document : texte imprimé Auteurs : H. F. Zhou, Auteur ; Y. Q. Ni, Auteur ; J. M. Ko, Auteur Année de publication : 2012 Article en page(s) : pp.785-796 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Dynamic  properties  Temperature  effects  Monitoring  Neural  networks  Damage  Identification  Cable  -  stayed  bridges  Vibration Résumé : False-positive or false-negative damage may be signaled by vibration-based structural damage detection methods when the environmental effects on the changes of dynamic characteristics of a structure are not accounted for appropriately. In this paper, a parametric approach for eliminating the temperature effect in vibration-based structural damage detection is proposed that is applicable to structures where dynamic properties and temperature are measured. First, a correlation model between damage-sensitive modal features and temperature is formulated with the back-propagation neural network (BPNN) technique. With the correlation model, the modal features measured under different temperature conditions are normalized to an identical reference status of temperature to eliminate the temperature effect. The normalized modal features are then applied for structural damage identification. The proposed approach is examined in the instrumented Ting Kau Bridge in Hong Kong. Using the long-term monitoring data of both modal frequencies and temperatures, a BPNN correlation model with validated generalization capability is formulated, and the normalized modal frequencies before and after damage are derived and applied for the structural damage alarm using the autoassociative neural network (AANN)–based novelty detection technique. The proposed approach is competent for eliminating the temperature effect and eschewing the false-positive damage alarm that originally occurred when using the measured modal frequencies directly. Case studies assuming damage at different structural components of the bridge are carried out to verify the proposed approach and the detectability of damage using the AANN-based novelty detection technique. The results show that the approach can detect damage when the damage-induced frequency change is as small as 1%. Nevertheless, it is worth mentioning that the frequency-based approach is most effective for detecting damage of a certain severity rather than detecting the onset of damage. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p785_s1?isAuthorized=no [article] Eliminating temperature effect in vibration - based structural damage detection [texte imprimé] / H. F. Zhou, Auteur ; Y. Q. Ni, Auteur ; J. M. Ko, Auteur . - 2012 . - pp.785-796. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.785-796 Mots-clés : Dynamic  properties  Temperature  effects  Monitoring  Neural  networks  Damage  Identification  Cable  -  stayed  bridges  Vibration Résumé : False-positive or false-negative damage may be signaled by vibration-based structural damage detection methods when the environmental effects on the changes of dynamic characteristics of a structure are not accounted for appropriately. In this paper, a parametric approach for eliminating the temperature effect in vibration-based structural damage detection is proposed that is applicable to structures where dynamic properties and temperature are measured. First, a correlation model between damage-sensitive modal features and temperature is formulated with the back-propagation neural network (BPNN) technique. With the correlation model, the modal features measured under different temperature conditions are normalized to an identical reference status of temperature to eliminate the temperature effect. The normalized modal features are then applied for structural damage identification. The proposed approach is examined in the instrumented Ting Kau Bridge in Hong Kong. Using the long-term monitoring data of both modal frequencies and temperatures, a BPNN correlation model with validated generalization capability is formulated, and the normalized modal frequencies before and after damage are derived and applied for the structural damage alarm using the autoassociative neural network (AANN)–based novelty detection technique. The proposed approach is competent for eliminating the temperature effect and eschewing the false-positive damage alarm that originally occurred when using the measured modal frequencies directly. Case studies assuming damage at different structural components of the bridge are carried out to verify the proposed approach and the detectability of damage using the AANN-based novelty detection technique. The results show that the approach can detect damage when the damage-induced frequency change is as small as 1%. Nevertheless, it is worth mentioning that the frequency-based approach is most effective for detecting damage of a certain severity rather than detecting the onset of damage. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p785_s1?isAuthorized=no

In - structure shock assessment of underground structures with consideration of rigid body motion / Guowei Ma in Journal of engineering mechanics, Vol. 137 N° 12 (Decembre 2011) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.797-806 Titre : In - structure shock assessment of underground structures with consideration of rigid body motion Type de document : texte imprimé Auteurs : Guowei Ma, Auteur ; Hongyuan Zhou, Auteur ; Karen Chong, Auteur Année de publication : 2012 Article en page(s) : pp.797-806 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Underground  structures  Blast  loads  Soil  -  structure  interactions  Structural  response  Response  spectra Résumé : The present study assesses the in-structure shock of an underground structure induced by a nearby subsurface detonation. Both the rigid body motion of the entirely buried structure and the local response of the structural element are considered in characterizing the in-structure shock. Soil-structure interaction, behaving as an interfacial damping, is taken into account, and the effect of different surrounding soils is investigated. A response spectrum is plotted for assessing in-structure shock induced by a typical subsurface detonation, and subsequently the safety of the internal facilities and equipment mounted on the buried structure is evaluated. For safety purposes, the protective structures are better constructed in a site with small acoustic impedance and a large attenuation factor. Results show that the proposed in-structure shock assessment method is effective and can be used as a supplement to TM-5-855-1 and TM-5-1300. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p797_s1?isAuthorized=no [article] In - structure shock assessment of underground structures with consideration of rigid body motion [texte imprimé] / Guowei Ma, Auteur ; Hongyuan Zhou, Auteur ; Karen Chong, Auteur . - 2012 . - pp.797-806. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.797-806 Mots-clés : Underground  structures  Blast  loads  Soil  -  structure  interactions  Structural  response  Response  spectra Résumé : The present study assesses the in-structure shock of an underground structure induced by a nearby subsurface detonation. Both the rigid body motion of the entirely buried structure and the local response of the structural element are considered in characterizing the in-structure shock. Soil-structure interaction, behaving as an interfacial damping, is taken into account, and the effect of different surrounding soils is investigated. A response spectrum is plotted for assessing in-structure shock induced by a typical subsurface detonation, and subsequently the safety of the internal facilities and equipment mounted on the buried structure is evaluated. For safety purposes, the protective structures are better constructed in a site with small acoustic impedance and a large attenuation factor. Results show that the proposed in-structure shock assessment method is effective and can be used as a supplement to TM-5-855-1 and TM-5-1300. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p797_s1?isAuthorized=no

Risk analysis of fatigue - induced sequential failures by branch - and - bound method employing system reliability bounds / Young-Joo Lee in Journal of engineering mechanics, Vol. 137 N° 12 (Decembre 2011) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) Titre : Risk analysis of fatigue - induced sequential failures by branch - and - bound method employing system reliability bounds Type de document : texte imprimé Auteurs : Young-Joo Lee, Auteur ; Junho Song, Auteur Année de publication : 2012 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Risk  management  Fatigue  Structural  systems  Structural  failures Résumé : Various types of structural systems are often subjected to the risk of fatigue-induced failures. If a structure does not have an adequate level of structural redundancy, local failures may initiate sequential failures and cause exceedingly large damage. For the risk-informed design and maintenance of such structural systems, it is thus essential to quantify the risk of fatigue-induced sequential failure. However, such risk analysis is often computationally intractable because one needs to explore innumerable failure sequences, each of which demands component and system reliability analyses in conjunction with structural analyses to account for various uncertainties and the effect of load redistributions. To overcome this computational challenge, many research efforts have been made to identify critical failure sequences with the highest likelihood and to quantify the overall risk by system reliability analysis based on the identified sequences. One of the most widely used approaches is the so-called “branch-and-bound” method. However, only the lower bound on the system risk is usually obtained because of challenges in system reliability analysis, while the changes of the lower bound by newly identified sequences are not diminishing monotonically. This paper aims to improve the efficiency and accuracy of risk analysis of fatigue-induced sequential failures by developing a new branch-and-bound method employing system reliability bounds (termed the B3 method). On the basis of a recursive formulation of the limit-state functions of fatigue-induced failures, a system failure event is formulated as a disjoint cut-set system event. A new search scheme identifies critical fatigue-induced failure sequences in the decreasing order of their probabilities while it systematically updates both lower and upper bounds on the system failure probability without additional system reliability analyses. As a result, the method can provide reasonable criteria for terminating the branch-and-bound search without missing critical failure sequences and reduce the number of computational simulations required to obtain reliable estimates on the system risk. The B3 method is tested and demonstrated by numerical examples of a multilayer Daniels system and a three-dimensional offshore structure. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p807_s1?isAuthorized=no [article] Risk analysis of fatigue - induced sequential failures by branch - and - bound method employing system reliability bounds [texte imprimé] / Young-Joo Lee, Auteur ; Junho Song, Auteur . - 2012. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) Mots-clés : Risk  management  Fatigue  Structural  systems  Structural  failures Résumé : Various types of structural systems are often subjected to the risk of fatigue-induced failures. If a structure does not have an adequate level of structural redundancy, local failures may initiate sequential failures and cause exceedingly large damage. For the risk-informed design and maintenance of such structural systems, it is thus essential to quantify the risk of fatigue-induced sequential failure. However, such risk analysis is often computationally intractable because one needs to explore innumerable failure sequences, each of which demands component and system reliability analyses in conjunction with structural analyses to account for various uncertainties and the effect of load redistributions. To overcome this computational challenge, many research efforts have been made to identify critical failure sequences with the highest likelihood and to quantify the overall risk by system reliability analysis based on the identified sequences. One of the most widely used approaches is the so-called “branch-and-bound” method. However, only the lower bound on the system risk is usually obtained because of challenges in system reliability analysis, while the changes of the lower bound by newly identified sequences are not diminishing monotonically. This paper aims to improve the efficiency and accuracy of risk analysis of fatigue-induced sequential failures by developing a new branch-and-bound method employing system reliability bounds (termed the B3 method). On the basis of a recursive formulation of the limit-state functions of fatigue-induced failures, a system failure event is formulated as a disjoint cut-set system event. A new search scheme identifies critical fatigue-induced failure sequences in the decreasing order of their probabilities while it systematically updates both lower and upper bounds on the system failure probability without additional system reliability analyses. As a result, the method can provide reasonable criteria for terminating the branch-and-bound search without missing critical failure sequences and reduce the number of computational simulations required to obtain reliable estimates on the system risk. The B3 method is tested and demonstrated by numerical examples of a multilayer Daniels system and a three-dimensional offshore structure. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p807_s1?isAuthorized=no

Effect of particle size on the characteristics of sand jets in water / Amir Hossein Azimi in Journal of engineering mechanics, Vol. 137 N° 12 (Decembre 2011) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.822-834 Titre : Effect of particle size on the characteristics of sand jets in water Type de document : texte imprimé Auteurs : Amir Hossein Azimi, Auteur ; David Z. Zhu, Auteur ; Nallamuthu Rajaratnam, Auteur Année de publication : 2012 Article en page(s) : pp.822-834 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Particle  size  Turbulence  Numerical  models  Computational  fluid  dynamics  technique Résumé : Sand jets in water have extensive engineering applications. A detailed numerical modeling of sand jets in water was conducted at high initial sand concentration using a commercial computational fluid dynamics package (ANSYS CFX 11.0). The results of the numerical simulation were first compared with some recent laboratory experiments. Simulations were then conducted to investigate the effect of sand particle sizes on velocity distribution, concentration profile, and turbulent properties. Turbulent flow characteristics, such as turbulent kinetic energy, turbulence intensity, rate of energy dissipation, and turbulent eddy frequency, were evaluated and the trend compared with the previous studies in the literature. The location of maximum kinetic energy was found to be independent of particle size. The turbulent kinetic energy and rate of dissipation of the water phase decrease with increasing particle size. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p822_s1?isAuthorized=no [article] Effect of particle size on the characteristics of sand jets in water [texte imprimé] / Amir Hossein Azimi, Auteur ; David Z. Zhu, Auteur ; Nallamuthu Rajaratnam, Auteur . - 2012 . - pp.822-834. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.822-834 Mots-clés : Particle  size  Turbulence  Numerical  models  Computational  fluid  dynamics  technique Résumé : Sand jets in water have extensive engineering applications. A detailed numerical modeling of sand jets in water was conducted at high initial sand concentration using a commercial computational fluid dynamics package (ANSYS CFX 11.0). The results of the numerical simulation were first compared with some recent laboratory experiments. Simulations were then conducted to investigate the effect of sand particle sizes on velocity distribution, concentration profile, and turbulent properties. Turbulent flow characteristics, such as turbulent kinetic energy, turbulence intensity, rate of energy dissipation, and turbulent eddy frequency, were evaluated and the trend compared with the previous studies in the literature. The location of maximum kinetic energy was found to be independent of particle size. The turbulent kinetic energy and rate of dissipation of the water phase decrease with increasing particle size. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p822_s1?isAuthorized=no

Analysis of turbulent hydraulic jump over a transitional rough bed of a rectangular channel / Noor Afzal in Journal of engineering mechanics, Vol. 137 N° 12 (Decembre 2011) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.835-845 Titre : Analysis of turbulent hydraulic jump over a transitional rough bed of a rectangular channel : Universal relations Type de document : texte imprimé Auteurs : Noor Afzal, Auteur ; A. Bushra, Auteur ; Abu Seena, Auteur Année de publication : 2012 Article en page(s) : pp.835-845 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Hydraulic  jump  Bed  roughness  Froude  number  Channels  Turbulent  flow Résumé : The streamwise flow structure of a turbulent hydraulic jump over a rough bed rectangular channel has been investigated. The flow is divided into inner and outer layers, where upstream supercritical flow changes to downstream subcritical flow. The analysis is based on depth averaged Reynolds momentum equations. The molecular viscosity on the rough bed imposes the no slip boundary condition, but close to the wall the turbulent process in inner layer provides certain matching conditions with the outer layer, where molecular viscosity has no dominant role. It is shown that the bed roughness in the inner layer has a passive role in imposing wall shear stress during formation of hydraulic jump in the outer layer. The Belanger’s jump condition of rectangular channel has been extended to account for the implications of the drag attributable to channel bed roughness, kinetic energy correction factor, and coefficient of the Reynolds normal stresses. For depth averaged Reynolds normal stress, an eddy viscosity model containing gradient of depth averaged axial velocity is considered. Analytical solutions for sequent depth ratio, jump length, roller length, and profiles of jump depth and velocity were found to depend upon the upstream Froude number, drag owing to bed roughness, and kinetic energy correction factor. On the basis of dynamical similarity, the roller length and aeration length were proposed to be of the same order as the jump length. An effective upstream Froude number, introduced in the present work, yields universal predictions for sequent depth ratio, jump length, roller length, jump profile, and other hydraulic jump characteristics that are explicitly independent of bed roughness drag. Thus, results for hydraulic jump over a rough bed channel can be directly deduced from classical smooth bed hydraulic jump theory, provided the upstream Froude number is replaced by the effective upstream Froude number. These findings of universality have been supported by experimental data over a rough bed rectangular channel. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p835_s1?isAuthorized=no [article] Analysis of turbulent hydraulic jump over a transitional rough bed of a rectangular channel : Universal relations [texte imprimé] / Noor Afzal, Auteur ; A. Bushra, Auteur ; Abu Seena, Auteur . - 2012 . - pp.835-845. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.835-845 Mots-clés : Hydraulic  jump  Bed  roughness  Froude  number  Channels  Turbulent  flow Résumé : The streamwise flow structure of a turbulent hydraulic jump over a rough bed rectangular channel has been investigated. The flow is divided into inner and outer layers, where upstream supercritical flow changes to downstream subcritical flow. The analysis is based on depth averaged Reynolds momentum equations. The molecular viscosity on the rough bed imposes the no slip boundary condition, but close to the wall the turbulent process in inner layer provides certain matching conditions with the outer layer, where molecular viscosity has no dominant role. It is shown that the bed roughness in the inner layer has a passive role in imposing wall shear stress during formation of hydraulic jump in the outer layer. The Belanger’s jump condition of rectangular channel has been extended to account for the implications of the drag attributable to channel bed roughness, kinetic energy correction factor, and coefficient of the Reynolds normal stresses. For depth averaged Reynolds normal stress, an eddy viscosity model containing gradient of depth averaged axial velocity is considered. Analytical solutions for sequent depth ratio, jump length, roller length, and profiles of jump depth and velocity were found to depend upon the upstream Froude number, drag owing to bed roughness, and kinetic energy correction factor. On the basis of dynamical similarity, the roller length and aeration length were proposed to be of the same order as the jump length. An effective upstream Froude number, introduced in the present work, yields universal predictions for sequent depth ratio, jump length, roller length, jump profile, and other hydraulic jump characteristics that are explicitly independent of bed roughness drag. Thus, results for hydraulic jump over a rough bed channel can be directly deduced from classical smooth bed hydraulic jump theory, provided the upstream Froude number is replaced by the effective upstream Froude number. These findings of universality have been supported by experimental data over a rough bed rectangular channel. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p835_s1?isAuthorized=no

Ring beam stiffness criterion for column - supported metal silos / Cem Topkaya in Journal of engineering mechanics, Vol. 137 N° 12 (Decembre 2011) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.846-853 Titre : Ring beam stiffness criterion for column - supported metal silos Type de document : texte imprimé Auteurs : Cem Topkaya, Auteur ; J. Michael Rotter, Auteur Année de publication : 2012 Article en page(s) : pp.846-853 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Silos  Cylindrical  shells  Closed  form  solutions  Curved  beams  Stiffness  Support  structures Résumé : Cylindrical metal silos are commonly elevated to provide access space beneath to directly discharge the contained materials into transportation systems. Evenly spaced column supports are commonly utilized. In larger silos, the discrete forces from supports are more evenly transferred and distributed into the cylindrical shell wall by using a ring beam. A fundamental assumption in the design of the silo shell is that the meridional compressive stresses are relatively uniformly distributed around the circumference. This assumption can easily be violated if the ring beam is flexible, so it is necessary to determine the ring stiffness needed to achieve a particular degree of uniformity of support. Current methods of assessing this stiffness rely on onerous finite-element analysis, which only provides information for the specific design being checked. In this paper, a criterion is developed to identify the required ring beam stiffness to achieve a particular degree of uniformity in the shell stresses. It is based on the ratio of the ring beam stiffness to the cylindrical shell stiffness in axial deformation in the fundamental harmonic mode of the column support, assuming that the ring is concentrically loaded and supported at equal intervals around the circumference. Vlasov’s curved beam is used to derive a closed-form solution for the ring beam stiffness and semimembrane theory for the cylindrical shell. The resulting stiffness ratio is verified using an extensive numerical study. It is shown that the method provides an effective means of determining the required stiffness of a supporting ring beam. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p846_s1?isAuthorized=no [article] Ring beam stiffness criterion for column - supported metal silos [texte imprimé] / Cem Topkaya, Auteur ; J. Michael Rotter, Auteur . - 2012 . - pp.846-853. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.846-853 Mots-clés : Silos  Cylindrical  shells  Closed  form  solutions  Curved  beams  Stiffness  Support  structures Résumé : Cylindrical metal silos are commonly elevated to provide access space beneath to directly discharge the contained materials into transportation systems. Evenly spaced column supports are commonly utilized. In larger silos, the discrete forces from supports are more evenly transferred and distributed into the cylindrical shell wall by using a ring beam. A fundamental assumption in the design of the silo shell is that the meridional compressive stresses are relatively uniformly distributed around the circumference. This assumption can easily be violated if the ring beam is flexible, so it is necessary to determine the ring stiffness needed to achieve a particular degree of uniformity of support. Current methods of assessing this stiffness rely on onerous finite-element analysis, which only provides information for the specific design being checked. In this paper, a criterion is developed to identify the required ring beam stiffness to achieve a particular degree of uniformity in the shell stresses. It is based on the ratio of the ring beam stiffness to the cylindrical shell stiffness in axial deformation in the fundamental harmonic mode of the column support, assuming that the ring is concentrically loaded and supported at equal intervals around the circumference. Vlasov’s curved beam is used to derive a closed-form solution for the ring beam stiffness and semimembrane theory for the cylindrical shell. The resulting stiffness ratio is verified using an extensive numerical study. It is shown that the method provides an effective means of determining the required stiffness of a supporting ring beam. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p846_s1?isAuthorized=no

Elastoplastic damaging model for adhesive anchor systems. I / Antonino Spada in Journal of engineering mechanics, Vol. 137 N° 12 (Decembre 2011) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.854-861 Titre : Elastoplastic damaging model for adhesive anchor systems. I : Theoretical formulation and numerical implementation Type de document : texte imprimé Auteurs : Antonino Spada, Auteur ; Giuseppe Giambanco, Auteur ; Piervincenzo Rizzo, Auteur Année de publication : 2012 Article en page(s) : pp.854-861 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Elastoplasticity  Damage  Pullout  Interfaces  Finite  element  method  Anchors  Implementation Résumé : In this and in the companion paper, the mechanical response of adhesive anchor systems is theoretically and numerically predicted and experimentally observed. The theoretical prediction is on the basis of an elastoplastic damaging model formulated to predict the structural response associated with the development of a fracture in adhesive anchor systems. This part describes the analytical model developed in the framework of a thermodynamically consistent theory, which assumes adhesion where the structure is sound, and friction in correspondence with the fracture. Isotropic damage is considered. The model can predict the structural behavior at the interface between two surfaces of ductile, brittle, or quasi-brittle materials. The Helmholtz free energy is written to model the materials’ hardening or softening. Isotropic damage is considered, and the possible effects of dilatancy are taken into account, including nonassociative flow rules. The formulation is implemented into the finite-element code FEAP. In the companion paper, the new model is adopted to predict the mechanical response to the pullout force of postinstalled rebar chemically bonded in concrete. The analytical model and the numerical implementation are experimentally validated by several pullout tests, which are monitored by using an acoustic-emission technique. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p854_s1?isAuthorized=no [article] Elastoplastic damaging model for adhesive anchor systems. I : Theoretical formulation and numerical implementation [texte imprimé] / Antonino Spada, Auteur ; Giuseppe Giambanco, Auteur ; Piervincenzo Rizzo, Auteur . - 2012 . - pp.854-861. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.854-861 Mots-clés : Elastoplasticity  Damage  Pullout  Interfaces  Finite  element  method  Anchors  Implementation Résumé : In this and in the companion paper, the mechanical response of adhesive anchor systems is theoretically and numerically predicted and experimentally observed. The theoretical prediction is on the basis of an elastoplastic damaging model formulated to predict the structural response associated with the development of a fracture in adhesive anchor systems. This part describes the analytical model developed in the framework of a thermodynamically consistent theory, which assumes adhesion where the structure is sound, and friction in correspondence with the fracture. Isotropic damage is considered. The model can predict the structural behavior at the interface between two surfaces of ductile, brittle, or quasi-brittle materials. The Helmholtz free energy is written to model the materials’ hardening or softening. Isotropic damage is considered, and the possible effects of dilatancy are taken into account, including nonassociative flow rules. The formulation is implemented into the finite-element code FEAP. In the companion paper, the new model is adopted to predict the mechanical response to the pullout force of postinstalled rebar chemically bonded in concrete. The analytical model and the numerical implementation are experimentally validated by several pullout tests, which are monitored by using an acoustic-emission technique. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p854_s1?isAuthorized=no

Elastoplastic damaging model for adhesive anchor systems. II / Antonino Spada in Journal of engineering mechanics, Vol. 137 N° 12 (Decembre 2011) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.862-876 Titre : Elastoplastic damaging model for adhesive anchor systems. II : Numerical and experimental validation Type de document : texte imprimé Auteurs : Antonino Spada, Auteur ; Rizzo, Piervincenzo, Auteur ; Giuseppe Giambanco, Auteur Année de publication : 2012 Article en page(s) : pp.862-876 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Pullout  Finite  element  method  Structural  health  monitoring  Elastoplasticity  Experimentation  Validation Résumé : This paper presents the numerical and experimental validation of the analytical elastoplastic damaging model proposed in the companion paper (Part I). The validation was carried out by describing the pullout failure of epoxy adhesive anchors. Pullout tests were simulated numerically and performed experimentally. Several specimens made of a rebar embedded in a hardened concrete cylinder by means of polyester resin were tested. Conventional strain gauges and acoustic emission (AE) sensors were used to evaluate the structural response of the system and to monitor the onset and progression of structural damage, respectively. The parametric analysis and the moment tensor analysis of the AE data were used to discriminate among different sources of damage. The results show the ability of the model to predict the response of the anchors and the suitability of the AE method to monitor damage onset and propagation and to discriminate among different source of damage. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p862_s1?isAuthorized=no [article] Elastoplastic damaging model for adhesive anchor systems. II : Numerical and experimental validation [texte imprimé] / Antonino Spada, Auteur ; Rizzo, Piervincenzo, Auteur ; Giuseppe Giambanco, Auteur . - 2012 . - pp.862-876. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.862-876 Mots-clés : Pullout  Finite  element  method  Structural  health  monitoring  Elastoplasticity  Experimentation  Validation Résumé : This paper presents the numerical and experimental validation of the analytical elastoplastic damaging model proposed in the companion paper (Part I). The validation was carried out by describing the pullout failure of epoxy adhesive anchors. Pullout tests were simulated numerically and performed experimentally. Several specimens made of a rebar embedded in a hardened concrete cylinder by means of polyester resin were tested. Conventional strain gauges and acoustic emission (AE) sensors were used to evaluate the structural response of the system and to monitor the onset and progression of structural damage, respectively. The parametric analysis and the moment tensor analysis of the AE data were used to discriminate among different sources of damage. The results show the ability of the model to predict the response of the anchors and the suitability of the AE method to monitor damage onset and propagation and to discriminate among different source of damage. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p862_s1?isAuthorized=no

Ultimate bearing capacity of reinforced concrete slab carrying concentrated load / Jinxin Gong in Journal of engineering mechanics, Vol. 137 N° 12 (Decembre 2011) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.877-886 Titre : Ultimate bearing capacity of reinforced concrete slab carrying concentrated load Type de document : texte imprimé Auteurs : Jinxin Gong, Auteur ; Yanqing Zhang, Auteur ; Shi Han, Auteur Année de publication : 2012 Article en page(s) : pp.877-886 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Concrete  slabs  Concentrated  loads  Load  bearing  capacity Résumé : Yield-line theory is accepted as a method for the design of reinforced concrete structures in many codes. Many guidelines have been provided to find the most possible failure mechanism and the lowest upper solution. Slabs equally reinforced in two normal directions, which fail in a fan mechanism under concentrated load, have been studied and ultimate bearing capacity for this kind of slab has been presented. Up to date, the ultimate bearing capacity of unequally reinforced slabs under concentrated load, so-called orthotropic slabs, has not been solved. This paper made an effort to solve this problem. Expression for ultimate bearing capacity of orthotropic reinforced concrete slab under concentrated load is derived in a polar system according to the principle of virtual works. On the basis of the variation principle, the equation of negative yield line is established, which gives the lowest upper solution. The equation of negative yield line for orthotropic reinforced concrete slab under concentrated load is found to be a symmetric and closed curve with determinate shape but indeterminate radius. The ultimate bearing capacity is dominated by bending or punching shear of slab, depending on the depth and the reinforcement ratio of the slab. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p877_s1?isAuthorized=no [article] Ultimate bearing capacity of reinforced concrete slab carrying concentrated load [texte imprimé] / Jinxin Gong, Auteur ; Yanqing Zhang, Auteur ; Shi Han, Auteur . - 2012 . - pp.877-886. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.877-886 Mots-clés : Concrete  slabs  Concentrated  loads  Load  bearing  capacity Résumé : Yield-line theory is accepted as a method for the design of reinforced concrete structures in many codes. Many guidelines have been provided to find the most possible failure mechanism and the lowest upper solution. Slabs equally reinforced in two normal directions, which fail in a fan mechanism under concentrated load, have been studied and ultimate bearing capacity for this kind of slab has been presented. Up to date, the ultimate bearing capacity of unequally reinforced slabs under concentrated load, so-called orthotropic slabs, has not been solved. This paper made an effort to solve this problem. Expression for ultimate bearing capacity of orthotropic reinforced concrete slab under concentrated load is derived in a polar system according to the principle of virtual works. On the basis of the variation principle, the equation of negative yield line is established, which gives the lowest upper solution. The equation of negative yield line for orthotropic reinforced concrete slab under concentrated load is found to be a symmetric and closed curve with determinate shape but indeterminate radius. The ultimate bearing capacity is dominated by bending or punching shear of slab, depending on the depth and the reinforcement ratio of the slab. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p877_s1?isAuthorized=no

Effect of inclined soil layers on surface vibration from underground railways using the thin - layer method / Simon Jones in Journal of engineering mechanics, Vol. 137 N° 12 (Decembre 2011) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.887-900 Titre : Effect of inclined soil layers on surface vibration from underground railways using the thin - layer method Type de document : texte imprimé Auteurs : Simon Jones, Auteur ; Hugh Hunt, Auteur Année de publication : 2012 Article en page(s) : pp.887-900 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Subways  Vibration  Layered  soils  Noise  pollution  Numerical  models Résumé : Noise and vibration from underground railways is a documented disturbance for individuals living or working near subways. Numerical models are used to investigate and understand vibration propagation from these underground railways, although the models commonly include simplifying assumptions (i.e., assuming the soil is a horizontally layered, homogenous half-space). Such simplifying assumptions add a level of uncertainty to the predictions that is not well understood. The goal of the current paper is to quantify the effect of including layer inclination angles up to 5° in relation to the surface. The thin-layer method (TLM) is introduced as an efficient and accurate means of simulating vibration from underground railways in arbitrarily layered half-spaces. The TLM is an element-based approach that uses the analytical wave equation to describe vibration in the horizontal direction, whereas assuming displacements in the vertical direction can be described by using a linear shape-function. The method is used to simulate a half-space with an inclined layer and is shown to be both accurate and computationally faster than a boundary-element model in predicting surface RMS velocities. The sensitivity of surface vibrations to inclination angle is also investigated, and the results suggest that small inclination angles of 5° or less can cause significant variation in RMS response of approximately 5 dB. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p887_s1?isAuthorized=no [article] Effect of inclined soil layers on surface vibration from underground railways using the thin - layer method [texte imprimé] / Simon Jones, Auteur ; Hugh Hunt, Auteur . - 2012 . - pp.887-900. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.887-900 Mots-clés : Subways  Vibration  Layered  soils  Noise  pollution  Numerical  models Résumé : Noise and vibration from underground railways is a documented disturbance for individuals living or working near subways. Numerical models are used to investigate and understand vibration propagation from these underground railways, although the models commonly include simplifying assumptions (i.e., assuming the soil is a horizontally layered, homogenous half-space). Such simplifying assumptions add a level of uncertainty to the predictions that is not well understood. The goal of the current paper is to quantify the effect of including layer inclination angles up to 5° in relation to the surface. The thin-layer method (TLM) is introduced as an efficient and accurate means of simulating vibration from underground railways in arbitrarily layered half-spaces. The TLM is an element-based approach that uses the analytical wave equation to describe vibration in the horizontal direction, whereas assuming displacements in the vertical direction can be described by using a linear shape-function. The method is used to simulate a half-space with an inclined layer and is shown to be both accurate and computationally faster than a boundary-element model in predicting surface RMS velocities. The sensitivity of surface vibrations to inclination angle is also investigated, and the results suggest that small inclination angles of 5° or less can cause significant variation in RMS response of approximately 5 dB. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p887_s1?isAuthorized=no

Modeling fracture and delamination of spray - applied fire - resisting materials under static and impact loads / Mahmud Dwaikat in Journal of engineering mechanics, Vol. 137 N° 12 (Decembre 2011) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.901-910 Titre : Modeling fracture and delamination of spray - applied fire - resisting materials under static and impact loads Type de document : texte imprimé Auteurs : Mahmud Dwaikat, Auteur ; Venkatesh Kodur, Auteur Année de publication : 2012 Article en page(s) : pp.901-910 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Cracking  Material  properties  Fire  resistance  Static  loads  Impact  loads  Laminated  materials Résumé : A specially developed two-dimensional cohesive zone finite element (CZFE) scheme is applied to simulate the fracture and delamination phenomena that occur in spray-applied fire-resisting material (SFRM) on steel structures. A cohesive zone material model for the SFRM is introduced and utilized to model both the internal cohesion in SFRM and the interfacial adhesion at the steel-SFRM interface. The CZFE model is validated by comparing predictions from the model with results from an adhesion test conducted at ambient temperature. The validated model is successfully applied to simulate the spontaneous initiation and propagation of cracks in the SFRM under static and impact loads. Results from the numerical studies indicate that the proposed model is capable of predicting the initiation and propagation of cracks within the insulation material and at the interface. The results show that the development of transverse cracks in the insulation layer help prevent further delamination of the SFRM. Also, it was found that for larger thicknesses of insulation, delamination occurs at less direct tension or flexural stresses. Results from impact simulations show that there is an optimum insulation thickness for resisting the delamination induced by impact loads. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p901_s1?isAuthorized=no [article] Modeling fracture and delamination of spray - applied fire - resisting materials under static and impact loads [texte imprimé] / Mahmud Dwaikat, Auteur ; Venkatesh Kodur, Auteur . - 2012 . - pp.901-910. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.901-910 Mots-clés : Cracking  Material  properties  Fire  resistance  Static  loads  Impact  loads  Laminated  materials Résumé : A specially developed two-dimensional cohesive zone finite element (CZFE) scheme is applied to simulate the fracture and delamination phenomena that occur in spray-applied fire-resisting material (SFRM) on steel structures. A cohesive zone material model for the SFRM is introduced and utilized to model both the internal cohesion in SFRM and the interfacial adhesion at the steel-SFRM interface. The CZFE model is validated by comparing predictions from the model with results from an adhesion test conducted at ambient temperature. The validated model is successfully applied to simulate the spontaneous initiation and propagation of cracks in the SFRM under static and impact loads. Results from the numerical studies indicate that the proposed model is capable of predicting the initiation and propagation of cracks within the insulation material and at the interface. The results show that the development of transverse cracks in the insulation layer help prevent further delamination of the SFRM. Also, it was found that for larger thicknesses of insulation, delamination occurs at less direct tension or flexural stresses. Results from impact simulations show that there is an optimum insulation thickness for resisting the delamination induced by impact loads. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p901_s1?isAuthorized=no

Response of open cell aluminum foams to fully reversed cyclic loading / Hernan Pinto in Journal of engineering mechanics, Vol. 137 N° 12 (Decembre 2011) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.911-918 Titre : Response of open cell aluminum foams to fully reversed cyclic loading Type de document : texte imprimé Auteurs : Hernan Pinto, Auteur ; Sanjay R. Arwade, Auteur ; Patrick Veale, Auteur Année de publication : 2012 Article en page(s) : pp.911-918 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Metals  (material)  Foam  Fatigue  Probability  Cyclic  loads Résumé : The response of metal foams to fully reversed cyclic loading has been investigated much less than the response to tension-tension and compression-compression cyclic loads. This paper describes tests of open cell aluminum foams that are subjected to fully reversed cyclic loading. Three different damage measures are evaluated as candidates for tracking the damage state in the material. These measures and associated failure criteria track the peak tensile stress, the peak compressive stress, and the ratio of the prepeak tensile and compressive material stiffnesses in each cycle. The peak tensile stress measure and criterion gave the most stable results. Finally, the fatigue lifetime is modeled by using a statistical Weibull model. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p911_s1?isAuthorized=no [article] Response of open cell aluminum foams to fully reversed cyclic loading [texte imprimé] / Hernan Pinto, Auteur ; Sanjay R. Arwade, Auteur ; Patrick Veale, Auteur . - 2012 . - pp.911-918. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.911-918 Mots-clés : Metals  (material)  Foam  Fatigue  Probability  Cyclic  loads Résumé : The response of metal foams to fully reversed cyclic loading has been investigated much less than the response to tension-tension and compression-compression cyclic loads. This paper describes tests of open cell aluminum foams that are subjected to fully reversed cyclic loading. Three different damage measures are evaluated as candidates for tracking the damage state in the material. These measures and associated failure criteria track the peak tensile stress, the peak compressive stress, and the ratio of the prepeak tensile and compressive material stiffnesses in each cycle. The peak tensile stress measure and criterion gave the most stable results. Finally, the fatigue lifetime is modeled by using a statistical Weibull model. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p911_s1?isAuthorized=no

Analytical solution for long - wave reflection by a rectangular obstacle with two scour trenches / Jian-Jian Xie in Journal of engineering mechanics, Vol. 137 N° 12 (Decembre 2011) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.919-930 Titre : Analytical solution for long - wave reflection by a rectangular obstacle with two scour trenches Type de document : texte imprimé Auteurs : Jian-Jian Xie, Auteur ; Huan-Wen Liu, Auteur ; Pengzhi Lin, Auteur Année de publication : 2012 Article en page(s) : pp.919-930 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Scour  Long  waves  Wave  reflection  Coefficients Résumé : In this paper, linear long-wave reflection by a rectangular obstacle with two scour trenches of power function profile is explored. A closed-form analytical solution in terms of the first and second kinds of Bessel functions is obtained, which finds two classic analytical solutions as its special cases, i.e., the wave reflection from a rectangular obstacle and from an infinite step. The phenomenon of zero reflection coefficient for a single rectangular obstacle with the same depths in front of and behind the obstacle still remains for a rectangular obstacle with two scour trenches as long as the bathymetry is symmetrical about the obstacle. The periodicity of the reflection coefficient as a function of the relative length of the middle rectangular obstacle disappears if two scour trenches are attached to the middle rectangular obstacle. Finally, the wave reflection by a rectangular obstacle with two scour trenches generally increases when the trenches become wide and deep. The wave reflection by a degenerated single slope increases when the slope becomes deep. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p919_s1?isAuthorized=no [article] Analytical solution for long - wave reflection by a rectangular obstacle with two scour trenches [texte imprimé] / Jian-Jian Xie, Auteur ; Huan-Wen Liu, Auteur ; Pengzhi Lin, Auteur . - 2012 . - pp.919-930. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 12 (Decembre 2011) . - pp.919-930 Mots-clés : Scour  Long  waves  Wave  reflection  Coefficients Résumé : In this paper, linear long-wave reflection by a rectangular obstacle with two scour trenches of power function profile is explored. A closed-form analytical solution in terms of the first and second kinds of Bessel functions is obtained, which finds two classic analytical solutions as its special cases, i.e., the wave reflection from a rectangular obstacle and from an infinite step. The phenomenon of zero reflection coefficient for a single rectangular obstacle with the same depths in front of and behind the obstacle still remains for a rectangular obstacle with two scour trenches as long as the bathymetry is symmetrical about the obstacle. The periodicity of the reflection coefficient as a function of the relative length of the middle rectangular obstacle disappears if two scour trenches are attached to the middle rectangular obstacle. Finally, the wave reflection by a rectangular obstacle with two scour trenches generally increases when the trenches become wide and deep. The wave reflection by a degenerated single slope increases when the slope becomes deep. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i12/p919_s1?isAuthorized=no

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