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Analytical solution of interface shear stresses in externally bonded FRP-strengthened concrete beams / Hayder A. Rasheed in Journal of engineering mechanics, Vol. 139 N° 1 (Janvier 2013) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 139 N° 1 (Janvier 2013) . - pp.18–28. Titre : Analytical solution of interface shear stresses in externally bonded FRP-strengthened concrete beams Type de document : texte imprimé Auteurs : Hayder A. Rasheed, Auteur ; Kyle H. Larson, Auteur ; Shahin Nayyeri Amiri, Auteur Année de publication : 2013 Article en page(s) : pp.18–28. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Concrete-composite  beams  FRP  Strengthening  Interface  shear  Delamination  Debonding Résumé : The fiber-reinforced polymer (FRP) plate or sheet debonding or cover delamination (concrete cover separation) failure mode in externally strengthened reinforced concrete beams has attracted a lot of attention. In this paper, a closed-form analytical solution is developed to determine the nonlinear shear stress distribution along the laminate interface and cover area for any load stage assuming a perfect bond. Trilinear moment-curvature and moment-extreme compression fiber strain is assumed to realize the analytical results. By differentiating the FRP axial tension force with respect to position along the beam, closed-form derivatives in terms of curvature and extreme compressive fiber strain are obtained. The results show three distinct regions of constant or stepwise linear shear distribution in each. These correspond to the uncracked, postcracked, and postyielded zones of the shear span. The results are shown to yield an exact match to those numerically obtained by dividing the shear spans into a large number of small segments and applying nonlinear sectional analysis in the middle of each segment. The analytical solution also compares well with the finite-element results using ABAQUS. The analysis of a number of strengthened beams at experimental debonding or cover delamination failure load show that the interface shear stress distribution varies from cases having no cracking at the plate tip (three regions) to those encountering two regions only (postcracked and postyielded) when the FRP plates or sheets extend close to the supports. It also shows that this distribution, at failure, consists of two regions in most of the cases and may only have a postcracked region in beams with relatively shorter plates or sheets. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000341 [article] Analytical solution of interface shear stresses in externally bonded FRP-strengthened concrete beams [texte imprimé] / Hayder A. Rasheed, Auteur ; Kyle H. Larson, Auteur ; Shahin Nayyeri Amiri, Auteur . - 2013 . - pp.18–28. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 139 N° 1 (Janvier 2013) . - pp.18–28. Mots-clés : Concrete-composite  beams  FRP  Strengthening  Interface  shear  Delamination  Debonding Résumé : The fiber-reinforced polymer (FRP) plate or sheet debonding or cover delamination (concrete cover separation) failure mode in externally strengthened reinforced concrete beams has attracted a lot of attention. In this paper, a closed-form analytical solution is developed to determine the nonlinear shear stress distribution along the laminate interface and cover area for any load stage assuming a perfect bond. Trilinear moment-curvature and moment-extreme compression fiber strain is assumed to realize the analytical results. By differentiating the FRP axial tension force with respect to position along the beam, closed-form derivatives in terms of curvature and extreme compressive fiber strain are obtained. The results show three distinct regions of constant or stepwise linear shear distribution in each. These correspond to the uncracked, postcracked, and postyielded zones of the shear span. The results are shown to yield an exact match to those numerically obtained by dividing the shear spans into a large number of small segments and applying nonlinear sectional analysis in the middle of each segment. The analytical solution also compares well with the finite-element results using ABAQUS. The analysis of a number of strengthened beams at experimental debonding or cover delamination failure load show that the interface shear stress distribution varies from cases having no cracking at the plate tip (three regions) to those encountering two regions only (postcracked and postyielded) when the FRP plates or sheets extend close to the supports. It also shows that this distribution, at failure, consists of two regions in most of the cases and may only have a postcracked region in beams with relatively shorter plates or sheets. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000341

Intelligent damage detection in bridge girders / Ahmed H. Al-Rahmani in Journal of engineering mechanics, Vol. 139 N° 3 (Mars 2013) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 139 N° 3 (Mars 2013) . - pp.296–304. Titre : Intelligent damage detection in bridge girders : hybrid approach Type de document : texte imprimé Auteurs : Ahmed H. Al-Rahmani, Auteur ; Hayder A. Rasheed, Auteur ; Yacoub Najjar, Auteur Année de publication : 2013 Article en page(s) : pp.296–304. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Damage  detection  Finite-element  analysis  Artificial  neural  network Résumé : This study is intended to facilitate damage detection in concrete bridge girders without the need for visual inspection while minimizing field measurements. Beams with different material and cracking parameters were modeled using ABAQUS finite-element analysis software to obtain stiffness values at specified nodes. The resulting database was then used to train an artificial neural network (ANN) model to inversely predict the most probable cracking pattern. The aim is to use the ANN approach to solve an inverse problem where a unique analytical solution is not attainable. Accordingly, simple span beams with three, five, seven, and nine stiffness nodes and a single crack were modeled in this work. To confirm that the ANN approach can characterize the logic within the databases, networks with geometric, material, and cracking parameters as inputs and stiffness values as outputs were created. These networks provided excellent prediction accuracy measures ([Math Processing Error]). For the inverse problem, the noted trend shows that better prediction accuracy measures are achieved when more stiffness nodes are used in the ANN modeling process. It was also observed that providing some outputs to the ANN as inputs, thus decreasing the number of required outputs, immensely improves the quality of predictions provided by the ANN. An experimental verification program will be conducted to qualify the effectiveness of the method proposed. This test program is described in details in the present paper. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000536 [article] Intelligent damage detection in bridge girders : hybrid approach [texte imprimé] / Ahmed H. Al-Rahmani, Auteur ; Hayder A. Rasheed, Auteur ; Yacoub Najjar, Auteur . - 2013 . - pp.296–304. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 139 N° 3 (Mars 2013) . - pp.296–304. Mots-clés : Damage  detection  Finite-element  analysis  Artificial  neural  network Résumé : This study is intended to facilitate damage detection in concrete bridge girders without the need for visual inspection while minimizing field measurements. Beams with different material and cracking parameters were modeled using ABAQUS finite-element analysis software to obtain stiffness values at specified nodes. The resulting database was then used to train an artificial neural network (ANN) model to inversely predict the most probable cracking pattern. The aim is to use the ANN approach to solve an inverse problem where a unique analytical solution is not attainable. Accordingly, simple span beams with three, five, seven, and nine stiffness nodes and a single crack were modeled in this work. To confirm that the ANN approach can characterize the logic within the databases, networks with geometric, material, and cracking parameters as inputs and stiffness values as outputs were created. These networks provided excellent prediction accuracy measures ([Math Processing Error]). For the inverse problem, the noted trend shows that better prediction accuracy measures are achieved when more stiffness nodes are used in the ANN modeling process. It was also observed that providing some outputs to the ANN as inputs, thus decreasing the number of required outputs, immensely improves the quality of predictions provided by the ANN. An experimental verification program will be conducted to qualify the effectiveness of the method proposed. This test program is described in details in the present paper. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000536