Academic literature on the topic 'Concrete plasticity damaged model'
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Journal articles on the topic "Concrete plasticity damaged model"
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Yang, Ke Jia, Zi Ling Xie, and Wei Li. "Application of RPC Constitutive Model in FEA." Applied Mechanics and Materials 578-579 (July 2014): 25–30. http://dx.doi.org/10.4028/www.scientific.net/amm.578-579.25.
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The damage evolution equation of RPC is established based on 2-parameter Weibull distribution. The constitutive relation of RPC is then calculated based on the damage evolution equation. The constitutive model of RPC is optimized by comparing experimental constitutive curve to models corresponding to different threshold strain. Based on the definition of damage index in ABAQUS, the damaged evolution equation in ABAQUS is recalculated based on the optimized constitutive relation. the concrete damaged plasticity model in ABAQUS is obtained using the aforementioned method. And the concrete damaged plasticity model is applied to three compression member and three simply supported beams with different reinforcements. The calculated stress-strain curve and deformation of three compression member and three beams is in accordance with the deformation characteristics of experiments, which verified the effectiveness of the proposed concrete damaged plasticity model of RPC.
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Ding, Hui, Jian Ping Wang, and Cheng Fan. "Application of Damaged Plasticity Model on Slab-Column Joints." Applied Mechanics and Materials 777 (July 2015): 13–17. http://dx.doi.org/10.4028/www.scientific.net/amm.777.13.
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By the analysis of reinforced concrete slab, combined with experiment tests the feasibility of damaged plasticity model for concrete. Using parametric analyses, further the plastic damage model of related parameters set methods were discussed, concrete dilatation Angle, viscous coefficient, tensile stiffness, tensile damage on the results, in order to the design of slab-column connections engineering personnel to provide the reference.
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Hanif, M. U., Z. Ibrahim, K. Ghaedi, A. Javanmardi, and S. K. Rehman. "Finite Element Simulation of Damage In RC Beams." Journal of Civil Engineering, Science and Technology 9, no. 1 (April 30, 2018): 50–57. http://dx.doi.org/10.33736/jcest.883.2018.
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A concrete damage model has been incorporated in finite element code ABAQUS as concrete damaged plasticity model to examine the sensitivity of the damage, as ABAQUS has the model that is capable of stiffness degradation in cracking which is the basis of fracture mechanics. Nonlinear constitutive relationships for concrete and steel have been incorporated in the model. The static and dynamic response of the structure at 10 different damage levels is studied and the sensitivity of the damage model towards the presence of non-linearity has been discussed. The concrete damaged plasticity model is capable of predicting formation of cracks in concrete beams against any kind of loads, as the results match with the experimental results. It can be concluded that the concrete damaged plasticity is a versatile tool for modeling RC structures and careful choice of solution procedures for dynamic analysis can lead to accurate modeling of concrete using a few routine laboratory test results of the materials.
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Dulinska, Joanna M. "Cooling Tower Shell under Asynchronous Kinematic Excitation Using Concrete Damaged Plasticity Model." Key Engineering Materials 535-536 (January 2013): 469–72. http://dx.doi.org/10.4028/www.scientific.net/kem.535-536.469.
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The paper presents the analysis of the dynamic response of a cooling tower to moderate earthquake. To represent inelastic behavior of the concrete material of the tower under dynamic loading, the concrete damaged plasticity constitutive model was assumed. The model consists of the combination of non-associated multi-hardening plasticity and scalar damaged elasticity to describe the irreversible damage that occurs during the fracturing process. Two different models of seismic excitation were used. Initially, a classical model of uniform kinematic excitation was applied. In this model it was assumed that excitation at all supports was identical. Then, a model of non-uniform kinematic excitation, typical for large multiple-support structures, was introduced. In that model the wave passage along the foundation ring was taken into account. It occurred that the assumption of asynchronous excitation led to the increase of the dynamic response of the tower with respect to the assumption of uniform ground motion. The tensile damage (cracking) in some parts of the tower appeared and the stiffness of the concrete was degraded when non-uniformity of excitation was considered. This was due to the quasi-static effects resulting from changes of subsoil geometry during the shock. The analysis indicated that the classical assumption of uniform excitation may lead to non-conservative assessment of the dynamic response of the shell described with concrete damaged plasticity model.
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Blikharskyy, Yaroslav. "Calculation of damage RC constructions according to deformation model." Theory and Building Practice 2020, no. 2 (November 20, 2020): 99–106. http://dx.doi.org/10.23939/jtbp2020.02.099.
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This article presents results of a theoretical study of reinforced concrete beams with damaged reinforcement. The change of micro-hardness of a reinforcing rebar’s with a diameter of 20 mm of A500C steel in the radial direction is investigated and the thickness of the heat-strengthened layer is established. It is established that the thickness of the thermo-strengthened steel layer of the reinforcing bar with a diameter of 20 mm of A500C is approximately 3 mm. It is shown that the strength characteristics of this layer are on 50% higher compared to the core material of the rebar, while the plasticity characteristics are lower. The aim of the work is to determine the strength and deformability of reinforced concrete structures without damaging the reinforcement and in case of damage. Determining the impact of changes in the physical characteristics of reinforcement on the damage of reinforced concrete structures, according to the calculation to the valid norms, in accordance with the deformation model. To achieve the goal of the work, theoretical calculations of reinforced concrete beams were performed according to the deformation model, according to valid norms. This technique uses nonlinear strain diagrams of concrete and rebar and is based on an iterative method. According to the research program 3 beam samples were calculated. Among them were undamaged control sample with single load bearing reinforcement of ∅20 mm diameter – BC-1; sample with ∅20 mm reinforcement with damages about 40% without changes in the physical and mechanical properties of reinforcement – BD-2 and sample with ∅20 mm reinforcement with damages about 40% with changes in the physical and mechanical properties of reinforcement – BD-3. The influence of change of physical and mechanical characteristics of rebar’s on bearing capacity of the damaged reinforced concrete beams is established.
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Ni, Zhen Qiang, and Qin Shu Cui. "Numerical Simulation of Z-Shaped Column Joints in RC Frame Based on Damage Plasticity Model." Applied Mechanics and Materials 777 (July 2015): 173–78. http://dx.doi.org/10.4028/www.scientific.net/amm.777.173.
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This research selected Z-shaped section column joints in RC frame as the investigating object and considered the mechanical parameters extracted from physical model test results, proposed the finite element model of concrete damaged plasticity. Combining concrete damage plasticity model parameters on ABAQUS of concrete constitutive relationship from appendix C of Code for design of concrete structures (GB50010-2010), add the concept of damage factor to Energy equivalence principle, construct finite element model of Z-shaped column joints in RC frame, and simulated the test process under horizontal cyclic loading. The analysis results indicate that the finite element model can perfectly simulate action. It can reflect the mechanical properties of Z-shaped column joints in frame under horizontal cyclic loading, which is proved correct and reliable.
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Wu, Hai Lin, Xiao Fan Du, Shi He Qin, Yao Li, and Qun Li. "Influence of Concrete Tension Softening Properties on the Steel-Liner Reinforced Concrete Penstock." Applied Mechanics and Materials 275-277 (January 2013): 1544–48. http://dx.doi.org/10.4028/www.scientific.net/amm.275-277.1544.
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In combination with the practice of a large hydropower station, concrete damaged plasticity model is introduced into the steel-liner reinforced concrete penstock for the nonlinear analysis, the damage distribution rules of the surrounding concrete and the stresses of the steels are furtherly studied under the different tension softening characteristic curves, the conclusions can provide the reference for damage assessment of the surrounding concrete and the optimization allocation of the reinforcement for the penstock.
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Szwed, Aleksander, and Inez Kamińska. "Modification of Concrete Damaged Plasticity model. Part I: Modified plastic potential." MATEC Web of Conferences 117 (2017): 00160. http://dx.doi.org/10.1051/matecconf/201711700160.
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Hafezolghorani, Milad, Farzad Hejazi, Ramin Vaghei, Mohd Saleh Bin Jaafar, and Keyhan Karimzade. "Simplified Damage Plasticity Model for Concrete." Structural Engineering International 27, no. 1 (February 2017): 68–78. http://dx.doi.org/10.2749/101686616x1081.
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Voyiadjis, George Z., Ziad N. Taqieddin, and Peter I. Kattan. "Anisotropic damage–plasticity model for concrete." International Journal of Plasticity 24, no. 10 (October 2008): 1946–65. http://dx.doi.org/10.1016/j.ijplas.2008.04.002.
Full textDissertations / Theses on the topic "Concrete plasticity damaged model"
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Bülow, Angeling Jenny. "Weight reduction of concrete poles for the Swedish power line grid : Using a Finite Element Model to optimize geometry in relation to load requirements." Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-66823.
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Because of an eventual ban of creosote-impregnated products, alternative materials for poles used in the electrical grid are needed. Concrete is one alternative and spun concrete poles have been manufactured for the Swedish grid before. These poles are still in use since the high strength and good functioning. However, they weigh too much in terms of the way that poles are assembled on the grid today. Therefore, a study comparing the capacity of different geometries, resulting in lower weight, is of interest. In this Master’s Thesis, crack initiation and compressive failure in concrete poles are examined by creating FE-models in the software BRIGADE/Plus, using concrete damage plasticity. Thus, guidance is provided about how thin the concrete walls can be made without risking failure – which also means how low the weight of such a pole can be. The failure most likely to occur is a compressive failure in the concrete with a ductile behavior. The result shows that a geometry change, which implies a thinner concrete wall, is possible. This means a weight reduction between 30-75 % or even more, depending on which network the poles are designed for.
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Vosoughian, Saeed. "The effect of pre-stressing location on punching shear capacity of concrete flat slabs." Thesis, KTH, Betongbyggnad, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-263243.
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Implementing pre-stressing cables is a viable option aiming at controlling deformation and cracking of concrete flat slabs in serviceability limit state. The pre-stressing cables also contribute to punching shear capacity of the slab when they are located in vicinity of the column. The positive influence of pre-stressing cables on punching capacity of the concrete slabs is mainly due to the vertical component of inclined cables, compressive in-plane stresses and counter acting bending moments near the support region. The method presented in Eurocode 2 to determine the punching capacity of the pre-stressed concrete flat slabs considers the in-plane compressive stresses but totally neglects the effect of counter acting moments. The effect of vertical forces introduced by inclined cables is only considered when they are within the distance 2d from the face of the column. This area is called basic control area in the Eurocode 2. In this master thesis nonlinear finite element analysis is carried out to study the effect of pre-stressing cables on punching shear capacity of concrete slabs respecting the distance of cables from the face of the column. To attain this objective, the concrete damage plasticity model is implemented to model the concrete. The results indicate that until the distance of 6d from the face of the column the contribution of pre-stressing cables in punching shear capacity of slabs is significant. Furthermore, comparing the numerical results with the punching shear capacity of slabs predicted by Eurocode 2 reveals that Eurocode tremendously underestimates the punching shear capacity when the cables are located outside the basic control area.
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Onifade, Ibrahim. "Development of Energy-based Damage and Plasticity Models for Asphalt Concrete Mixtures." Doctoral thesis, KTH, Byggnadsmaterial, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-198663.
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Characterizing the full range of damage and plastic behaviour of asphalt mixtures under varying strain-rates and stress states is a complex and challenging task. One reason for this is partly due to the strain rate and temperature dependent nature of the material as well as the variation in the properties of the constituent materials that make up the composite asphalt mixture. Existing stress-based models for asphalt concrete materials are developed based on mechanics principles, but these models are, however, limited in their application for actual pavement analysis and design since rate dependency parameters are needed in the constitutive model to account for the influence of the strain rate on the stress-based yield and evolution criteria. Till date, we are yet to arrive at simple and comprehensive constitutive models that can be used to model the behaviour of asphalt mixture over a wide range of strain-rate which is experienced in the actual pavement sections. The aim of this thesis is to develop an increased understanding of the strength and deformation mechanism of asphalt mixtures through multi-scale modeling and to develop simple and comprehensive continuum models to characterize the non-linear behaviour of the material under varying stress-states and conditions. An analysis framework is developed for the evaluation of the influence of asphalt mixture morphology on its mechanical properties and response using X-Ray CT and digital image processing techniques. The procedure developed in the analysis framework is then used to investigate the existence of an invariant critical energy threshold for meso-crack initiation which serves as the basis for the development of a theory for the development of energy-based damage and plastic deformation models for asphalt mixtures. A new energy-based viscoelastic damage model is developed and proposed based on continuum damage mechanics (CDM) and the thermodynamics of irreversible processes. A second order damage variable tensor is introduced to account for the distributed damage in the material in the different principal damage directions. In this way, the material response in tension and compression can be decoupled and the effects of both tension- and compression stress states on the material behaviour can be accounted for adequately. Based on the finding from the energy-based damage model, an equivalent micro-crack stress approach is developed and proposed for the damage and fracture characterization of asphalt mixtures. The effective micro-crack stress approach takes account of the material stiffness and a critical energy threshold for micro-crack initiation in the characterization of damage and fracture properties of the mixture. The effective micro-crack stress approach is developed based on fundamental mechanics principles and it reduces to the Griffith's energy balance criterion when purely elastic materials are considered without the need for the consideration of the surface energy and a crack size in the determination of the fracture stress. A new Continuum Plasticity Mechanics (CPM) model is developed within the framework of thermodynamics to describe the plastic behaviour of asphalt concrete material with energy-based criteria derived for the initiation and evolution of plastic deformation. An internal state variable termed the "plasticity variable" is introduced to described the distributed dislocation movement in the microstructure. The CPM model unifies aspects of existing elasto-plastic and visco-plastic theories in one theory and shows particular strength in the modeling of rate-dependent plastic behaviour of materials without the need for the consideration of rate dependency parameters in the constitutive relationships. The CPM model is further extended to consider the reduction in the stiffness properties with incremental loading and to develop a unified energy-based damage and plasticity model. The models are implemented in a Finite Element (FE) analysis program for the validation of the models. The result shows that the energy-based damage and plastic deformation models are capable of predicting the behaviour of asphalt concrete mixtures under varying stress-states and strain-rate conditions. The work in this thesis provides the basis for the development of more fundamental understanding of the asphalt concrete material response and the application of sound and solid mechanics principles in the analysis and design of pavement structures.En heltäckande karakterisering av skador och plastiska beteende hos asfaltblandningar under varierande belastningshastighet och spänningstillstånd är en komplex och svår uppgift. En orsak till detta är relaterat till materialets belastningshastighet- och temperaturberoende, såväl som variationen i materialegenskaperna hos de ingående komponenterna i den sammansatta asfaltblandningen. Befintliga spänningsbaserade modeller för asfaltbetongmaterial är utvecklade baserade på mekanikprinciper, men dessa modeller är begränsade när det gäller analys och design av verkliga asfaltsbeläggningar eftersom hastighetsberoende parametrar behövs i den konstitutiva modellen även med hänsyn till töjningshastighetens inverkan på kriterier för gränser och utveckling av spänningstillstånd. Det finns därför behov av att utveckla enkla men ändå heltäckande konstitutiva modeller som kan användas för att modellera beteendet hos asfaltmassan över ett brett spektrum av belastningshastigheter för olika av sektioner asfaltsbeläggningar. Syftet med denna avhandling är att öka förståelsen av hållfasthets- och deformationsmekanismer för asfaltblandningar genom multi-modellering. Målet är att utveckla enkla och heltäckande kontinuummodeller som karakteriserar materialets olinjära beteende under varierande spänningstillstånd och betingelser. Ett analysramverk har utvecklats för utvärdering av påverkan av asfaltmassans morfologi på dess mekaniska egenskaper och beteende med hjälp av röntgendatortomografi och digital bildbehandlingsteknik. Detta förfarande har sedan använts för att undersöka förekomsten av inneboende kritiska tröskelvärden för brottenergin för mesosprickinitiering vilket i sin tur ligger till grund för utvecklingen av en teori för modellering av energibaserade skador och plastisk deformation hos asfaltblandningar. En ny energidensitet baserad viskoelastisk skademodell utvecklas och föreslås utgå från kontinuum-skade-mekanik (CDM) och termodynamik för irreversibla processer. En andra ordningens skadevariabeltensor införs för att ta hänsyn till skadedistributionen i materialen i de olika principiella skaderiktningarna. På detta sätt kan materialets respons i drag- och tryckbelastning separeras och effekterna av spänningstillstånd i både drag och tryck kan beaktas på ett adekvat sätt. Baserat på resultaten från den energibaserade skademodellen utvecklas och föreslås en motsvarande metod för mikrosprickspänning gällande skade- och brottkarakteriseringen av asfaltblandningar. Metoden för den effektiva mikrosprickspänningen tar hänsyn till materialets styvhet och en kritisk tröskelenergi för mikrosprickinitiering för karakteriseringen av skador och brottegenskaper hos blandningen. Denna metod är utvecklad baserat på grundläggande mekanikprinciper och kan för rent elastiska material reduceras till Griffiths energibalanskriterium utan hänsyn till ytenergi och sprickstorlek vid bestämningen av brottspänningen. En ny termodynamikbaserad modell för kontinuumplasticitetsmekanik (CPM) utvecklas för att beskriva det plastiska beteendet hos asfaltbetongmaterial med energibaserade kriterier härledda för initiering och progression av plastisk deformation. En intern tillståndsvariabel kallad "plasticitetvariabeln" införs för att beskriva den fördelade dislokationsrörelsen i mikrostrukturen. CPM-modellen förenar befintliga elasto-plastiska och visko-plastiska teorier i en teori och visar sig vara särskilt effektiv i modelleringen av hastighetsberoende plastiskt beteende hos material utan att behöva beakta hastighetsberoende parametrar i de konstitutiva sambanden. CPM-modellen utvidgas ytterligare för att kunna beakta reduktionen av styvheten med stegvis ökad belastning och för att utveckla en enhetlig energibaserad skade- och plasticitetmodell. Modellerna är implementerade i ett finit element (FE)-analysprogram för validering av modellerna. Resultatet visar att de energibaserade modellerna för skador och plastisk deformation kan förutsäga beteendet hos asfaltbetongblandningar under varierande spänningstillstånd och töjningshastighetsförhållanden. Arbetet i denna avhandling utgör grunden för utvecklingen av mer grundläggande förståelse av asfaltbetongmaterialets respons och tillämpningen av sunda och robusta mekanikprinciper i analys och design av asfaltstrukturer.
QC 20161220
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Farahmandpour, Chia. "Modélisation et simulation du comportement des bétons confinés." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066550/document.
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Les techniques de renforcement de structures en béton armé (BA) par collage de polymères renforcés de fibres (PRF) trouvent un important champ d'applications dans le renforcement des poteaux en BA. Le chemisage par PRF confine le noyau du poteau et permet d'augmenter sa résistance et sa ductilité. Bien que de nombreux travaux expérimentaux aient été consacrés à l'étude de l'effet de confinement du PRF sur le comportement des poteaux en BA, la réalisation d'une simulation réaliste de la réponse structurelle de tels éléments présente de nombreuses difficultés liées aux modèles de comportement peu appropriés à reproduire précisément la réponse mécanique du béton confiné. Dans cette recherche, un modèle de comportement élasto-plastique endommageable est développé pour reproduire la réponse mécanique du béton sollicité suivant un chemin triaxial de contraintes. Ce modèle prend en compte différents mécanismes de comportement du béton tels que les déformations irréversibles, l'endommagement dû à la microfissuration, la sensibilité au confinement et les caractéristiques de dilatation. Un processus d'identification des paramètres du modèle est proposé sur la base d'essais classiques. La validation de ce modèle est ensuite démontrée en comparant des résultats de simulations à des données expérimentales de la littérature sur des bétons confinés activement puis des bétons confinés par des PRF présentant une large gamme de rigidité. Le modèle proposé est également comparé à différentes modélisations de la littérature. Les capacités du modèle sont illustrées et analysées sur des applications tridimensionnelles de poteaux en BA de taille réelle, non confinés et confinés par PRFFor the past two decades, externally bonded Fiber Reinforced Polymers (FRP) has gained much popularity for seismic rehabilitation of reinforced concrete (RC) columns. In this technique, FRP wrap installed on the surface of a column acts as lateral confinement and enhance the strength and deformation capacity of the concrete element. Although many experimental works have been devoted to the study of confining effect of FRP on the behavior of RC columns, the numerical simulation of FRP-jacketed RC columns remains a challenging issue due to the lack of appropriate constitutive model for confined concrete. In this study, a damage plastic model is developed to predict the behavior of concrete under triaxial stress states. The proposed model takes into account different material behavior such as irreversible strain, damage due to microcracking, confinement sensitivity and dilation characteristic. A straightforward identification process of all model’s parameters is then presented. The identification process is applied to different normal strength concrete. The validity of the model is then demonstrated through confrontation of experimental data with simulations considering active confined concrete and FRP confined concrete with a wide range of confinement stiffness. The proposed constitutive model is also compared with other models from the literature and the distinguishing features of this new model are discussed. Furthermore, the capacity of the model in the three-dimensional finite element analysis of full-scale RC columns is demonstrate and discussed
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Santos, Fernanda de Oliveira. "Modelo constitutivo incremental explícito para o concreto confinado baseado na teoria da plasticidade e dano." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-10072018-114442/.
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O confinamento de pilares de concreto por meio de camisas de aço ou compósitos possui uma função importante na preservação, recuperação e reforço de estruturas, pois proporciona aumento de resistência e ductilidade desses elementos estruturais. Porém, grande parte dos modelos existentes apresenta limitações na previsão do comportamento do concreto confinado, principalmente por serem dependentes do tipo de confinamento. Portanto, este trabalho apresenta um modelo para descrição do comportamento tensão-deformação do concreto submetido a qualquer tipo de confinamento uniforme, ativo ou passivo, e confinado com diferentes materiais confinantes - aço ou compósitos. O modelo constitutivo associa plasticidade e dano a fim de prever adequadamente a resistência, deformabilidade e redução de rigidez elástica do concreto confinado. O modelo é desenvolvido para um processo incremental explícito de implementação, permitindo, portanto, o seu desenvolvimento em qualquer tipo de planilha. Finalmente, o modelo foi validado por meio de um conjunto representativo de experimentos encontrados na literatura.Confinement of concrete columns through steel or composites jackets has an important function in the preservation, recovery and strengthening of structures, because it provides increased strength and ductility of these structural elements. However, most of the existing models have limitations in the prediction of the behavior of confined concrete, mainly because they are dependent on the type of confinement. This work presents a model for the description of the stress-strain behavior of the concrete submitted to any type of uniform confinement, active or passive, and confined with different confinement materials, steel or composites. The constitutive model associates plasticity and damage in order to predict with accuracy the strength, ultimate strain and reduction of elastic stiffness of the confined concrete. The model is developed by an explicit incremental implementation process allowing, therefore, its development in any type of spreadsheet. Finally, the model was validated through a representative set of experiments found in the literature.
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Tahar, Benabdellah. "Câ†2 continuous hardening/softening elasto-plasticity model for concrete." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323061.
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Li, Tianbai. "Stress integration strategies for a new hardening/softening elasto-plasticity model for structural concrete." Thesis, University of Sheffield, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425181.
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Salman, Kehlan. "A new elasto-plasticity constitutive model for concrete under multiaxial compression based on experimental observations." Thesis, University of Sheffield, 2007. http://etheses.whiterose.ac.uk/10295/.
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This thesis comprises of two different kinds of work. The first part is focussed on existing experimental data. Investigations and observations of the behaviour of plain concrete under triaxial and multiaxial compression following cyclic loading and a variety of stress paths has been presented. The behaviour of concrete with different constituents was also investigated. The directions of the plastic strain vectors were identified. Two loading surface were also identified: (i) the Peak Nominal Stress surface (PNS) which was identified from the peak stresses recorded from stress control tests and (ii) the Volume Transition Stress surface (VTS) which determines the onset of the volumetric dilation. The plastic VTS is the surface which was identified from plastic strain components only. At this surface, the directions of the plastic strain vectors are purely deviatoric. A proposal for the shapes of the yield surface for concrete is given. These shapes were identified by the plastic work contours and also from the directions of the plastic strain vectors assuming the associated flow rule. This assumption has been verified by examining the normality of the plastic strain vectors to the PNS surface. Following the investigation of the experimental data, an examination of various advanced plasticity models for concrete revealed the need to develop a new constitutive model with a suitable shape of the loading surfaces and with a better prediction for the stress-strain response. A new constitutive model for plain concrete has been developed using the previous work in this field at the University of Sheffield. The new yield surface was developed as a combination of a reflection of part of the peak nominal stress surface (PNS) and a quartic function. The continuity, the convexity and the normality of the yield surfaces were ensured. The model was calibrated and the optimum values of the thirteen material constants are presented. This is followed by a sensitivity study with simulations of a wide range of existing experimental data. Simulations of concrete with different constituents are also presented. The formulation of the model was simplified and verified by using numerical derivatives. A comparative study between the analytical and numerical derivatives of the constitutive model is presented. The sensitivity study and the simulations of experimental tests showed that the new constitutive model is: (i) easy to calibrate using only data from uniaxial compression tests and one triaxial compression test, and (ii) gives very good predictions of stressstrain response of different types of concrete under triaxial compression stresses and at different levels of confinement all the way to the peak stress state.
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Neeli, Yeshwanth Sai. "Use of Photogrammetry Aided Damage Detection for Residual Strength Estimation of Corrosion Damaged Prestressed Concrete Bridge Girders." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/99445.
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Corrosion damage reduces the load-carrying capacity of bridges which poses a threat to passenger safety. The objective of this research was to reduce the resources involved in conventional bridge inspections which are an important tool in the condition assessment of bridges and to help in determining if live load testing is necessary. This research proposes a framework to link semi-automated damage detection on prestressed concrete bridge girders with the estimation of their residual flexural capacity. The framework was implemented on four full-scale corrosion damaged girders from decommissioned bridges in Virginia. 3D point clouds of the girders reconstructed from images using Structure from Motion (SfM) approach were textured with images containing cracks detected at pixel level using a U-Net (Fully Convolutional Network). Spalls were detected by identifying the locations where normals associated with the points in the 3D point cloud deviated from being perpendicular to the reference directions chosen, by an amount greater than a threshold angle. 3D textured mesh models, overlaid with the detected cracks and spalls were used as 3D damage maps to determine reduced cross-sectional areas of prestressing strands to account for the corrosion damage as per the recommendations of Naito, Jones, and Hodgson (2011). Scaling them to real-world dimensions enabled the measurement of any required dimension, eliminating the need for physical contact.
The flexural capacities of a box beam and an I-beam estimated using strain compatibility analysis were validated with the actual capacities at failure sections determined from four destructive tests conducted by Al Rufaydah (2020). Along with the reduction in the cross-sectional areas of strands, limiting the ultimate strain that heavily corroded strands can develop was explored as a possible way to improve the results of the analysis. Strain compatibility analysis was used to estimate the ultimate rupture strain, in the heavily corroded bottommost layer prestressing strands exposed before the box beam was tested. More research is required to associate each level of strand corrosion with an average ultimate strain at which the corroded strands rupture. This framework was found to give satisfactory estimates of the residual strength. Reduction in resources involved in current visual inspection practices and eliminating the need for physical access, make this approach worthwhile to be explored further to improve the output of each step in the proposed framework.Master of Science
Corrosion damage is a major concern for bridges as it reduces their load carrying capacity. Bridge failures in the past have been attributed to corrosion damage. The risk associated with corrosion damage caused failures increases as the infrastructure ages. Many bridges across the world built forty to fifty years ago are now in a deteriorated condition and need to be repaired and retrofitted. Visual inspections to identify damage or deterioration on a bridge are very important to assess the condition of the bridge and determine the need for repairing or for posting weight restrictions for the vehicles that use the bridge. These inspections require close physical access to the hard-to-reach areas of the bridge for physically measuring the damage which involves many resources in the form of experienced engineers, skilled labor, equipment, time, and money. The safety of the personnel involved in the inspections is also a major concern. Nowadays, a lot of research is being done in using Unmanned Aerial Vehicles (UAVs) like drones for bridge inspections and in using artificial intelligence for the detection of cracks on the images of concrete and steel members. Girders or beams in a bridge are the primary longitudinal load carrying members. Concrete inherently is weak in tension. To address this problem, High Strength steel reinforcement (called prestressing steel or prestressing strands) in prestressed concrete beams is pre-loaded with a tensile force before the application of any loads so that the regions which will experience tension under the service loads would be subjected to a pre-compression to improve the performance of the beam and delay cracking. Spalls are a type of corrosion damage on concrete members where portions of concrete fall off (section loss) due to corrosion in the steel reinforcement, exposing the reinforcement to the environment which leads to accelerated corrosion causing a loss of cross-sectional area and ultimately, a rupture in the steel. If the process of detecting the damage (cracks, spalls, exposed or severed reinforcement, etc.) is automated, the next logical step that would add great value would be, to quantify the effect of the damage detected on the load carrying capacity of the bridges. Using a quantified estimate of the remaining capacity of a bridge, determined after accounting for the corrosion damage, informed decisions can be made about the measures to be taken. This research proposes a stepwise framework to forge a link between a semi-automated visual inspection and residual capacity evaluation of actual prestressed concrete bridge girders obtained from two bridges that have been removed from service in Virginia due to extensive deterioration. 3D point clouds represent an object as a set of points on its surface in three dimensional space. These point clouds can be constructed either using laser scanning or using Photogrammetry from images of the girders captured with a digital camera. In this research, 3D point clouds are reconstructed from sequences of overlapping images of the girders using an approach called Structure from Motion (SfM) which locates matched pixels present between consecutive images in the 3D space. Crack-like features were automatically detected and highlighted on the images of the girders that were used to build the 3D point clouds using artificial intelligence (Neural Network). The images with cracks highlighted were applied as texture to the surface mesh on the point cloud to transfer the detail, color, and realism present in the images to the 3D model. Spalls were detected on 3D point clouds based on the orientation of the normals associated with the points with respect to the reference directions. Point clouds and textured meshes of the girders were scaled to real-world dimensions facilitating the measurement of any required dimension on the point clouds, eliminating the need for physical contact in condition assessment. Any cracks or spalls that went unidentified in the damage detection were visible on the textured meshes of the girders improving the performance of the approach. 3D textured mesh models of the girders overlaid with the detected cracks and spalls were used as 3D damage maps in residual strength estimation. Cross-sectional slices were extracted from the dense point clouds at various sections along the length of each girder. The slices were overlaid on the cross-section drawings of the girders, and the prestressing strands affected due to the corrosion damage were identified. They were reduced in cross-sectional area to account for the corrosion damage as per the recommendations of Naito, Jones, and Hodgson (2011) and were used in the calculation of the ultimate moment capacity of the girders using an approach called strain compatibility analysis. Estimated residual capacities were compared to the actual capacities of the girders found from destructive tests conducted by Al Rufaydah (2020). Comparisons are presented for the failure sections in these tests and the results were analyzed to evaluate the effectiveness of this framework. More research is to be done to determine the factors causing rupture in prestressing strands with different degrees of corrosion. This framework was found to give satisfactory estimates of the residual strength. Reduction in resources involved in current visual inspection practices and eliminating the need for physical access, make this approach worthwhile to be explored further to improve the output of each step in the proposed framework.
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Navarro, Menargues Miguel. "Estudio numérico parametrizado del punzonamiento en losas de hormigón armado. Evaluación del refuerzo estructural." Doctoral thesis, Universidad de Alicante, 2018. http://hdl.handle.net/10045/83429.
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En el presente trabajo se aborda la tesis “Estudio paramétrico con FEM del refuerzo a punzonamiento de losas de hormigón armado”. Se trata de todo lo relacionado con el fenómeno resistente de punzonamiento en estructuras, especialmente en forjados construidos mediante hormigón armado. Se trata de cuatro apartados bien diferenciados. En este, el primero, se desarrolla la síntesis de la tesis, donde se marcan unos objetivos, seguido de una explicación detallada y descripción de este fenómeno mediante su estado del arte, que abarca el grueso de éste primer apartado, en el cual se describen, entre otros aspectos, las diferentes patologías producidas por el punzonamiento y casos de sucesos catastróficos que provocaron, la historia de los forjados y los principales estudios llevados a cabo sobre este fenómeno, y acabando con las principales resultados y conclusiones de la tesis. Después, el segundo y tercer apartado contienen los artículos publicados y no publicados, respectivamente, por capítulos. Por último, se desarrollan las conclusiones en el último y cuarto apartado.
Book chapters on the topic "Concrete plasticity damaged model"
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Sannametla, Nidhi, and Jyosyula Sri Kalyana Rama. "Seismic Response of UHPC Strengthened Reinforced Concrete Frame Using Concrete Damaged Plasticity Model." In Lecture Notes in Civil Engineering, 159–71. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-4079-0_14.
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Vorlet, S., P. Manso, and G. De Cesare. "Seismic Behavior of Pine Flat Concrete Gravity Dam Using Microplane Damage-Plasticity Model." In Lecture Notes in Civil Engineering, 353–67. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-51085-5_19.
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Aymerich, F., L. Fenu, and G. Loi. "FE Analysis of the Flexural Behavior of Cementitious Composites Using the Concrete Damage Plasticity Model." In Lecture Notes in Civil Engineering, 124–33. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-23748-6_10.
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Chen, J. F., and Y. Tao. "Finite Element Modelling of FRP-to-Concrete Bond Behaviour Using the Concrete Damage Plasticity Theory Combined with a Plastic Degradation Model." In Advances in FRP Composites in Civil Engineering, 45–50. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-17487-2_7.
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Thomas, T. "3 Equilibrium (Plasticity) Truss Model." In Unired Theory of Reinforced Concrete, 75–122. CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742: CRC Press, 2017. http://dx.doi.org/10.1201/9780203734650-4.
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Fan, Ying Fang, Zhi Qiang Hu, and Jing Zhou. "Inspection and Model Experiment of a Damaged Arch Bridge." In Engineering Plasticity and Its Applications, 223–28. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-433-2.223.
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"A note on the ABAQUS Concrete Damaged Plasticity (CDP) model." In Civil, Architecture and Environmental Engineering, 1301–6. CRC Press, 2017. http://dx.doi.org/10.1201/9781315226187-239.
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"Non-local plasticity softening model for brittle materials." In Fracture and Damage of Concrete and Rock - FDCR-2, 60–69. CRC Press, 1993. http://dx.doi.org/10.1201/9781482271287-9.
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Chandrasekaran, Srinivasan, and P. T. Ajesh Kumar. "Damage assessment in concrete marine structures using damage plasticity model." In Progress in the Analysis and Design of Marine Structures, 733–44. CRC Press, 2017. http://dx.doi.org/10.1201/9781315157368-95.
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Ghaedi, Khaled, Farzad Hejazi, Meisam Gordan, Ahad Javanmardi, Hamed Khatibi, and Ali Joharchi. "Seismic Response Characteristics of RCC Dams Considering Fluid-Structure Interaction of Dam-Reservoir System." In Computational Overview of Fluid Structure Interaction. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.97859.
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In analysis of different types of dams, i.e. arch, gravity, rockfill and Roller Compacted Concrete (RCC) dams, the effect of hydrodynamic water pressure as an effective factor must seriously be taken into consideration. In present study, the hydrodynamic effect is precisely deliberated in RCC dams and compared to hydrostatic pressure effect. For this purpose, Kinta RCC dam in Malaysia is selected and 2D finite element (FE) model of the dam is performed. The Lagrangian approach is used to solve the dam-reservoir interaction, fluid–structure interaction (FSI), and in order to evaluate the crack pattern, Concrete Damaged Plasticity (CDP) model is implemented. Comparisons show that hydrodynamic pressure significantly changes the dam behaviour under seismic excitations. Moreover, the hydrodynamic effect modifies the deformation shape of the dam during the ground motions, however, it increases the magnitudes of the developed stresses causing more extensive tension crack damages mostly in the heel and upstream zones of the dam.
Conference papers on the topic "Concrete plasticity damaged model"
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Li, W., and J. Wu. "A note on the ABAQUS Concrete Damaged Plasticity (CDP) model." In Proceedings of the International Conference on Civil, Architecture and Environmental Engineering (ICCAE2016). CRC Press/Balkema P.O. Box 11320, 2301 EH Leiden, The Netherlands: CRC Press/Balkema, 2017. http://dx.doi.org/10.1201/9781315116242-42.
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Grassl, P. "Modelling the dynamic response of concrete with the damage plasticity model CDPM2." In 10th International Conference on Fracture Mechanics of Concrete and Concrete Structures. IA-FraMCoS, 2019. http://dx.doi.org/10.21012/fc10.235633.
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Chandrasekaran, Srinivasan, and P. Kumar. "Damage assessment in concrete marine structures using damage plasticity model." In Proceedings of the 6th International Conference On Marine Structures (Marstruct 2017). CRC Press/Balkema P.O. Box 11320, 2301 EH Leiden, The Netherlands: CRC Press/Balkema, 2017. http://dx.doi.org/10.1201/9781315157368-84.
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Altaee, Mohammed, Majid Kadhim, Sarmed Altayee, and Ali Adheem. "Employment of damage plasticity constitutive model for concrete members subjected to high strain-rate." In Proceedings of the 1st International Multi-Disciplinary Conference Theme: Sustainable Development and Smart Planning, IMDC-SDSP 2020, Cyperspace, 28-30 June 2020. EAI, 2020. http://dx.doi.org/10.4108/eai.28-6-2020.2298164.
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Yu, Hailing, David Jeong, John Choros, and Ted Sussmann. "Finite Element Modeling of Prestressed Concrete Crossties With Ballast and Subgrade Support." In ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/detc2011-47452.
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With the first major installation in North American railroads during the 1960’s, concrete ties were believed to last longer than timber ties and have the potential for reduced life cycle costs. However, their characteristic response to initial pretension release as well as dynamic track loading is not well understood. In North America, concrete ties have been found vulnerable to rail seat deterioration (RSD), but the mechanisms contributing to RSD failures are not well understood. To improve such understanding, a comprehensive computational study of the tie response to dynamic track forces is needed. This paper presents an initial research effort in this direction that models concrete crossties as heterogeneous media in three-dimensional finite element analyses, i.e., the prestressing strands, concrete matrix and the strand-concrete interfaces are represented explicitly. Damaged plasticity models are employed for the concrete material, and linear elastic bond-slip relations, followed by damage initiation and evolution, are adopted for the strand-concrete interfaces. Further, the ballast is modeled with an Extended Drucker-Prager plasticity model, and the subgrade is modeled as an elastic half space. All material parameters are obtained from the open literature. Currently the rail fastening systems are not included in modeling. Two loading scenarios are simulated: pretension release and direct rail seat loading. The modeling approach is able to predict the deformed tie shape, initial interface deterioration, the compressive stress state in concrete and residual tension in the strands upon pretension release. The transfer lengths of the prestressing strands can be readily calculated from the analysis results. Further predicted are the rail seat force-displacement characteristics and the potential failure mode of a concrete crosstie under direct rail seat loading. The responses of two railroad concrete crossties with 8-strand and 24-wire reinforcements, respectively, are studied using the presented modeling framework. The analyses indicate a potential failure mode of tensile cracking at the tie base below the rail seats. The results show that the 24-wire tie is better able to retain the pretension in the reinforcements than the 8-strand tie, resulting in slightly stronger rail seat force-displacement characteristics and higher failure load. The effects of the load application method and the subgrade modeling on the predicted tie response are further studied.
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Hou, Gangling, Chenning Song, Tianshu Song, and Guoliang Zhou. "Analysis of Factors Influencing Compressive Bearing Capacity of Nuclear Containment." In 2013 21st International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icone21-15191.
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Nuclear containment protects nuclear island from serious accident, while its compressive bearing capacity remains the key problem to nuclear safety. With reference to one nuclear containment, the special concrete damaged plasticity model in software ABAQUS, this article systematically analyzes influencing rules of compressive bearing capacity and factors such as gravity, steel liner, prestressed tendons etc. The result shows that steel liner and prestressed tendons play key parts in deformation inhibition and the failure mode of nuclear containment, meanwhile prestressed tendons are crucial to improve the compressive bearing capacity.
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Yu, Hailing, and David Jeong. "Railroad Tie Responses to Directly Applied Rail Seat Loading in Ballasted Tracks: A Computational Study." In 2012 Joint Rail Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/jrc2012-74149.
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This paper describes work in-progress that applies the finite element (FE) method in predicting the responses of individual railroad crossties to rail seat pressure loading in a ballasted track. Both wood and prestressed concrete crossties are examined. The concrete tie is modeled as a heterogeneous medium with prestressing wires or strands embedded in a concrete matrix. The constitutive relations employed in the models are: elasticity followed by damaged plasticity for the concrete material, linear elastic bond-slip relations with potential initiation and evolution of damage to the bond for the steel-concrete interfaces, orthotropic elasticity followed by failure dictated by orthotropic stress criteria for the wood ties, extended Drucker-Prager plasticity for the granular and frictional ballast material, and elastic half space for the subgrade. The corresponding material parameters are obtained from the open literature. Under a simplified pressure load uniformly distributed over the rail seat area, the FE method predicts tensile cracking at the tie base below the rail seats of a concrete tie and compressive failure in the rail seats of a wood tie. The rail seat force-displacement relations are obtained from the simulations. The resultant rail seat forces at which tie failures occur are compared for concrete and wood ties. The FE method appears to be a promising tool for studying the railroad tie behavior under rail seat loading conditions in a ballasted track. Experimental data will be sought to calibrate the material parameters and verify the modeling approach. Additional track components, particularly rails, rail pads and fasteners, will be incorporated in future modeling efforts. This detailed modeling approach may help to shed light on the rail seat deterioration failure mechanisms observed in some concrete ties.
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Yu, Hailing. "Finite Element Analysis of Contributing Factors to the Horizontal Splitting Cracks in Concrete Crossties Pretensioned With Seven-Wire Strands." In 2017 Joint Rail Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/jrc2017-2256.
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This paper employs the finite element (FE) modeling method to investigate the contributing factors to the “horizontal” splitting cracks observed in the upper strand plane in some concrete crossties made with seven-wire strands. The concrete tie is modeled as a concrete matrix embedded with prestressing steel strands. A damaged plasticity model that can predict the onset and propagation of tensile degradation is applied to the concrete material. An elasto-plastic bond model developed in-house is applied to the steel-concrete interface to account for the interface bond-slip mechanisms and particularly the dilatational effects that can produce the splitting forces. The pretension release process is simulated statically, followed by the dynamic simulations of cyclic rail seat loading. The concrete compressive strength at which the pretension in the strands is released, or release strength, affects both the concrete behavior and the bond characteristics. Three concrete release strengths, 3500, 4500 and 6000 psi, are considered in the simulations. Concrete tie models without and with a fastening system are developed and simulated to examine the effect of embedded fastener shoulders and fastener installation. The fastener shoulders are seated relatively deeply reaching between the two rows of strands. There is instant concrete material degradation adjacent to the strand interfaces near the tie ends upon pretension release. Without the fastening system in the model, the 3500 psi release strength leads to a high degree of degradation that is coalesced and continuous in the upper and lower strand planes, respectively. The damage profiles with the higher release strengths are more discrete and disconnected. Dynamic loading appears to increase the degree of degradation over time. In all cases, the upper strand plane is not dominant in the degree or the extent of material degradation, in contrast to the field observations that the horizontal splitting occurred in the upper strand plane only. Further simulations with the fastener model at 3500 psi concrete release strength indicate that the fastener installation process does not worsen the damage profile. However, the presence of fastener shoulders in the concrete matrix changes the stress distribution and redirects more concrete damages to the upper strand plane, while leaving disconnected damages in the lower strand plane. Under repeated dynamic rail loading, this potentially reproduces the exact upper strand plane, horizontal cracking pattern observed in the field. Subjected to further experimental verification, the FE analyses identify three contributing factors to the horizontal macro-cracks occurring at the specific upper strand level: (1) relatively low concrete release strength during production, (2) embedded fastener shoulders that redistribute concrete damages to the upper strand plane, and (3) a sufficiently large number of dynamic rail loading cycles for the microscopic damages to develop into macro-cracks. The number of dynamic loading cycles needed to produce macro-cracks should increase with the increased concrete release strength.
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Ka¨hko¨nen, Jukka, and Pentti Varpasuo. "Using Microplane Material Model for Concrete in Soft Missile Impact Analysis." In 18th International Conference on Nuclear Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/icone18-29142.
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The paper describes basis of a microplane concrete material model which was implemented in a commercial FE -code using user subroutine interface. The material model is called M4. The motivation for this implementation was a need for a concrete model which would perform well in a soft missile impact analysis. Numerical integration over the surface of a unit sphere is crucial to microplane material models. We tested our microplane implementation using several numerical integration formulas presented in literature. The two fairly simple test cases described in this paper revealed clearly the numerical anisotropy induced by the integration formulations. The impact problem was a medium size, medium velocity soft missile impact test case from an international research program. We compared our implementation of M4 model to a tensorial based damage plasticity concrete model and found out that the results were almost identical. However, the numerical results did not agree well with the measurements in this test case. We concluded this disagreement might be consequence of nonlinear phenomena beyond material constitutive relations.
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Yu, Hailing. "Estimating Deterioration in the Concrete Tie-Ballast Interface Based on Vertical Tie Deflection Profile: A Numerical Study." In 2016 Joint Rail Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/jrc2016-5783.
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In ballasted concrete tie track, the tie-ballast interface can deteriorate resulting in concrete tie bottom abrasion, ballast pulverization and/or voids in tie-ballast interfaces. Tie-ballast voids toward tie ends can lead to unfavorable center binding support conditions that can result in premature concrete tie failure and possible train derailment. Direct detection of these conditions is difficult. There is a strong interest in assessing the concrete tie-ballast interface conditions indirectly using measured vertical deflections. This paper seeks to establish a link between the vertical deflection profile of a concrete tie top surface and the tie-ballast interface condition using the finite element analysis (FEA) method. The concrete tie is modeled as a concrete matrix embedded with prestressing steel strands or wires. The configurations of two commonly used concrete ties, one with 8 prestressing strands and the other with 20 prestressing wires, are employed in this study. All models are three-dimensional and symmetric about the tie center. A damaged plasticity model that can predict onset and propagation of tensile cracks is applied to the concrete material. The steel-concrete interface is homogenized and represented with a thin layer of cohesive elements sandwiched between steel and concrete elements. Strand- or wire-specific elasto-plastic bond models developed at the Volpe Center are applied to the cohesive elements to account for the interface bonding mechanisms. FE models are developed for both original and worn concrete ties, with the latter assuming hypothetical patterns of reduced cross sections resulting from abrasive interactions with the ballast. Static analyses of pretension release in these concrete ties are conducted, and vertical deflection gradients along tie lengths are calculated and shown to correspond well with the worn cross sectional patterns for a given reinforcement type. The ballast is further modeled with Extended Drucker-Prager plasticity, and hypothetical voids are applied toward the tie ends along the concrete tie-ballast interface to simulate center binding support conditions. The distance range over which the concrete tie is supported in the center is variable and yields different center binding severity. Static simulations are completed with vertical rail seat loads applied on the concrete tie-ballast assembly. The influences of various factors on the vertical deflection profile, including tie type, vertical load magnitude, center binding severity, cross sectional material loss and prestress loss, are examined based on the FEA results. The work presented in this paper demonstrates the potential of using the vertical deflection profile of concrete tie top surfaces to assess deteriorations in the tie-ballast interface. The simulation results further help to clarify minimum technical requirements on inspection technologies that measure concrete tie vertical deflection profiles.
Reports on the topic "Concrete plasticity damaged model"
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Vogler, Tracy, and Christopher James Lammi. A Nonlocal Peridynamic Plasticity Model for the Dynamic Flow and Fracture of Concrete. Office of Scientific and Technical Information (OSTI), October 2014. http://dx.doi.org/10.2172/1159446.
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