Top PDF Damage plastic model for concrete failure under impulsive loadings

Damage plastic model for concrete failure under impulsive loadings

Damage plastic model for concrete failure under impulsive loadings

The IRIS 2012 benchmark [1] was devoted to compare various modelling of impact on reinforced concrete slabs. Its aim was to improve the methods used and to provide guidance to assess the integrity of structures impacted by missiles. During this benchmark, it appeared that damage plastic models developed in commercial software worked reasonably well to predict structural damage. This is the reason why a 3D constitutive model of this type, named DPDC (Damage Plastic Dynamic Concrete), was elaborated and introduced in EUROPLEXUS, a general finite element code for fast transient analysis of structures jointly developed by the CEA and the European Commission (EC – JRC ISPRA) and other partners of whom EDF. The model developed for industrial purposes should have been robust, efficient and easy to use. It was freely inspired by [2] whose model presents a sound theoretical basis and a reliable calibration procedure.
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Elastoplastic nonlocal damage model for concrete and size effect analysis

Elastoplastic nonlocal damage model for concrete and size effect analysis

0.2 0.2 Figure 4: Geometry and loading setup of CDB. A satisfactory agreement of the experimental and numerical results is observed. Fig. 5 provides a com- parison of the experimental crack pattern with the nu- merical damage profile of the plastic damage model. As seen in the experiments, flexural damage band (mode I) starts first at midspan (stage A). Further load increase leads to the development of the flex- ural damage band and a propagation of damage (mode I & II) continues over the support (stage B), then a shear damage band (pure mode II) formed sud- denly (stage C). Finally, failure occurs at the load in- troduction zone near the loading column (stage D). The ultimate failure load obtained experimentally was 1180 kN , the corresponding numerical value is 1285 kN , which is overestimated by 11%. Thus, the
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Damage Models for Concrete

Damage Models for Concrete

3 ANISOTROPIC DAMAGE MODEL 3.1 V ALIDITY Microcracking is usually geometrically oriented as a result of the loading history on the material. In tension, microcracks are perpendicular to the tensile stress direction; in compression microcracks open parallel to the compressive stress direction. Although a scalar damage model, which does not account for directionality of damage, might be a sufficient approximation in usual applications, i.e., when tensile failure is expected with a quasi-radial loading path, damage-induced anisotropy is required for more complex loading histories. The influence of crack closure is needed in the case of alternated loads: microcracks may close and the effect of damage on the material stiffness disappears. Finally, plastic strains are observed when the material unloads in compression. The following section describes a constitutive relation based on elastoplastic damage which addresses these issues. This anisotropic damage model has been compared to experimental data in tension, compression, compression–shear, and nonradial tension– shear. It provides a reasonable agreement with such experiments [3].
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Intrinsic dissipation of a modular anisotropic damage model : application to concrete under impact

Intrinsic dissipation of a modular anisotropic damage model : application to concrete under impact

Figure 21: Vertical displacement of the projectile: comparison between experiment and simulation. tension and 25000 J/m 3 in compression in quasi-static. The role of strain rate effect introduced through the delay- damage law on the dissipation due to damage is very important from a strain rate of 100.s −1 since the dissipation at failure is multiplied by 71 in that case. Comparison with experimental results, which has not be done yet, is crucial in that case. This should bring the future work towards a better identification of the delay-damage law, and in particular, the post-peak response in dynamics. Indeed, no experiments enable to identify directly the post-peak part of the stress-strain response in dynamics, intrinsic dissipation would be an interesting alternative for identification.
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A novel multi-fiber Timoshenko beam finite element formulation with embedded discontinuities to describe reinforced concrete failure under static loadings

A novel multi-fiber Timoshenko beam finite element formulation with embedded discontinuities to describe reinforced concrete failure under static loadings

CNRS, 3SR, F38000 Grenoble, France e-mail: stephane.grange@ujf-grenoble.fr Key words: Timoshenko, Multi-fiber, Discontinuity Abstract. A novel multi-fiber beam finite element formulation based on the Timoshenko model is proposed in this paper to simulate failure of reinforced concrete structural elements subjected to static monotonic loadings. The beam section can have an arbitrary shape and each fiber has a local constitutive law representing a specific material. The embedded discontinuity concept is adopted to enrich the displacement field of the fibers in order to describe the opening of cracks and the develop- ment of plastic hinges. The material behavior at the discontinuity is characterized by a cohesive law linking the axial stress and the displacement jump by a linear relation, which allows capturing the released fracture energy. The variational formulation is presented in the context of the incompatible modes method. Moreover, the additional modes are statically condensed at the element level. The corresponding computational procedure is detailed in the paper. Several numerical applications and general remarks are finally provided to illustrate the performance of the proposed element.
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Anisotropic 3D delay-damage model to simulate concrete structures

Anisotropic 3D delay-damage model to simulate concrete structures

† DEN/DM2S/SEMT, CEA Saclay, 91191 Gif-sur-Yvette cedex gatuingt@lmt.ens-cachan.fr ABSTRACT. High dynamic loadings lead to material degradation and structural failure. This is even more the case for concrete structures where the parts initially in compression break in ten- sion due to waves propagation and reflection. The dissymmetry of the material behavior plays a major role in such cases, dissymmetry mainly due to damage induced anisotropy. Loading induced damage is most often anisotropic and one proposes here to take advantage of such a feature to build a damage model for concrete, dissymmetric in tension and in compression, 3D, suitable for dynamic computations. A single 2nd order tensorial damage variable D D D is consid-
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Elastoplastic nonlocal damage model for concrete and size effect analysis

Elastoplastic nonlocal damage model for concrete and size effect analysis

Elastoplastic nonlocal damage model for concrete and size effect analysis A. Krayani, F. Dufour & G. Pijaudier-Cabot ERT R&DO, GeM, Ecole Centrale de Nantes, France ABSTRACT: This work deals with a combination of plasticity and nonlocal damage formulation for mod- elling concrete structure behaviour subjected to mixed mode failure. Plastic effect, driven by effective stress, is an hardening process and accounts for the development of irreversible strains while softening is controlled by damage to describe the degradation of the material stiffness. A regularization technique, based on the im- plicit gradient definition of the nonlocal strain tensor, is introduced to overcome the deficiencies induced by the softening damage relation i.e., spurious strain localization and dependance of the energy dissipation on mesh refinement. A 3D tensile bar localization benchmark is used to validate the effectiveness of the regularization technique. Moreover, simulation of reinforced concrete continuous deep beam is studied to illustrate the im- provements achieved by coupled law compared to scalar damage models. Finally, size effect in mixed mode failure is investigated by mean of three asymmetric four-point bending tests on notched specimens.
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A micromechanical inspired model for the coupled to damage elasto-plastic behavior of geomaterials under compression

A micromechanical inspired model for the coupled to damage elasto-plastic behavior of geomaterials under compression

1 Introduction Many works have been devoted to the modeling of the mechanical behavior of geomaterials like concrete, rocks, and soils and many phenomenological models have been proposed to give an account of the main aspects of the observed phenomena, namely, dilatancy and stress soften- ing, while those materials are submitted to triaxial compressions. The majority of these approaches is based on elasto-plastic formalism with some of them having resort to damage coupling. For instance, in soil or rock mechanics, one generally uses elasto-plastic or more generally (thermo)elasto-viscoplastic models without in- troducing damage variables [ 1 – 3 ], whereas it is generally admitted that one cannot reproduce the experimental results observed for concrete without considering a damage evolution law [ 4 – 10 ]. In all the cases the elasto-plastic models are based on a restricted choice of yield criteria (like Drucker –Prager one or some variants like Hoek–Brown criterion [ 1 , 2 ] or the cap model [ 11 ]), with common feature being the hypothesis of a nonassociative flow rule. The reason generally invoked to put aside the normality rule for the plasticity evolution is that otherwise a too important dilatancy effects would be obtained in the evolution of the volumetric strain once the normality rule is used, for instance, for a standard Drucker –Prager-type criterion.
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Plastic and fracture behavior of a dual phase steel sheet under quasi-static and dynamic loadings

Plastic and fracture behavior of a dual phase steel sheet under quasi-static and dynamic loadings

ductile failure criterion known as the Modified Mohr–Coulomb[ 15 , 16 ] (MMC) criterion, which is usually used to describe the failure of brittle materials. This MMC criterion can predict the strain at failure for a wide range of stress triaxiality and Lode angle combinations. The MMC criterion was further extended in [ 17 ] using the Hershey [ 18 ] /Hosford [ 19 ] equivalent stress instead of the Tresca stress [ 20 ]. According to the authors, a better prediction under plane stress conditions is obtained. The Hosford-Coulomb failure criterion was also improved to introduce the effect of other phenomena such as strain-rate dependency [ 6 ] or more recently necking e ffect [ 21 , 22 ] for shell element applications. However, any improvement of these criteria leads to an increase of the number of parameters to identify and requires complex testing procedures to measure the plastic strain at failure for various stress triaxialities and Lode angle values. Moreover, using fracture criteria, damage does not influence the elasto-plastic behavior. This means that stress softening is not represented, which can cause a poor description of strain localization and of the crack path as the material does not lose its load-carrying capacity. From the numerical point of view, another difficulty may arise when performing simulations for dynamic problems (e.g. crash): when a critical value is reached for a given number of integration points in an element, this “sound” (i.e. undamaged) element is removed from the computation. This causes a sudden drop of the stresses at the material point that can lead to dynamic instabilities.
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Bayesian updating of a cracking model for reinforced concrete structures subjected to static and cyclic loadings

Bayesian updating of a cracking model for reinforced concrete structures subjected to static and cyclic loadings

ABSTRACT Several reinforced concrete structures fail by fatigue loads. The effects of this type of loading are complex. Many mechanical models based on the damage theory could be used to represent the behavior of reinforced concrete under cyclic loading. Their use requires, among others, knowledge of the material characteristic parameters and its related uncertainties that could be determined from experimental tests. However the models are time-consuming and the experimental data scarce. In this paper we propose a Bayesian network based methodology to propagate uncertainties in the damage theory model. The proposed methodology is useful to identify the uncertainties of the damage model used when some parameters are measured. The methodology is illustrated with a reinforced concrete beam subjected to cyclic loading. The results obtained were compared with those of the experimental tests to validate the proposed methodology. The good agreement indicates that our approach is capable of propagating uncertainties and integrating data from experimental tests. The proposed approach could be also used to identify the uncertainties of the model used by introducing experimental measurements.
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Experimental validation of an anisotropic delay damage model for impact on reinforced concrete structures

Experimental validation of an anisotropic delay damage model for impact on reinforced concrete structures

Impact problems on reinforced concrete structures are usually computed with models coupling plasticity and isotropic damage. The induced damage anisotropy observed for quasi-brittle materials such as concrete is often reproduced considering different variables for tension and compression (not consistent with the thermodynamic framework). Introducing viscosity for both damage and plasticity evolutions enables to reproduce the strength enhancement due to rate effects. Such kinds of models present the main advantage to describe precisely each phenomenon locally observed (different rate effects in traction and compression, compaction under confined loadings ...) but require a large number of parameters. Anisotropic damage is quite relevant to describe the micro-cracking pattern and the failure conditions of quasi-brittle materials and structures. In concrete, a state of micro-cracks orthogonal to the loading direction in tension and parallel to it in compression is easily described by a second order damage variable. This anisotropic delay-damage model, used in this work, introduces only few parameters (7 including elasticity parameters E and ν) compared to the ones mentioned higher. The effi- ciency and the validation of such an approach is illustrated with its application on impacted reinforced concrete beams and dynamic Brazilian tests. The test has been performed with the drop-weight tower ORION of the CEA Saclay for two kinds of beam geometries in order to exhibit flexion and shear rupture.
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Stress-strain model for FRP-confined concrete columns under cyclic and seismic loading

Stress-strain model for FRP-confined concrete columns under cyclic and seismic loading

Keywords: FRP; Confined-concrete; Stress-strain model; Cyclic loading; Multifiber beam. 1 INTRODUCTION Mitigation of the seismic vulnerability of existing structures is an important issue in earthquake engineering. Fiber-reinforced polymer (FRP) is often adopted from among a wide range of technical solutions suitable for seismic upgrading of reinforced-concrete (RC) structures. This paper presents the formulation of a 1D (global) stress-strain concrete constitutive model suitable for monotonic and cycling loadings. The proposed model deals with internal (due to transverse steel reinforcement -TSR- ) and external confinement (due to FRP), and considers the crack opening-and-closure mechanism. It was inspired by the La Borderie's cyclic model for (unconfined) concrete based on damage mechanics and Eid & Paultre’s confined-concrete model based on experimental studies. Validation is provided using experimental results on RC-retrofitted columns (8 isolated columns and 1 bridge-pier mockup) subjected to cyclic and pseudo-dynamic loadings. Numerical computations were performed with multifiber Timoshenko beam elements, introduced in the finite-element code FEDEASLab (a MATLAB toolbox).
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A micromechanical inspired model for the coupled to damage elasto-plastic behavior of geomaterials under compression

A micromechanical inspired model for the coupled to damage elasto-plastic behavior of geomaterials under compression

Key words: Plasticity, Damage, compression test, geomaterials, dilatancy 1. Introduction Many works have been devoted to the modeling of the mechanical behavior of geo-materials like concrete, rocks and soils and many phenomenological models have been proposed to give an account of the main aspects of the observed phenomena, namely dilatancy and stress softening, while those materials are submitted to triaxial compressions. The majority of these approaches is based on elasto-plastic formalism with some of them having resort to damage coupling. For instance, in soil or rock mechanics one generally uses elasto-plastic or more generally (thermo)- elasto-viscoplastic models without introducing damage variables [12, 7, 6], whereas it is generally admitted that one cannot reproduce the experimental results observed for concrete without considering a damage evolution law [14, 15, 18, 22, 5, 21, 23]. In all the cases the elasto-plastic models are based on a restricted choice of yield criteria (like Drucker-Prager one or some variants like Hoek-Brown criterion [12, 7] or the cap model [3]), with common feature being the hypothesis of a non associative flow rule. The reason generally invoked to put aside the normality rule for the plasticity evolution is that otherwise a too important dilatancy effects would be obtained in the evolution of the volumetric strain once the normality rule is used, for instance for a standard Drucker-Prager type criterion.
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An elastic plastic damage formulation for concrete

An elastic plastic damage formulation for concrete

Tension dominant applications have not been considered in this paper. Due to strain and damage localisation it is well established that simulated responses are expected to be mesh dependent (see for instance [37] or 17] ). Qualitative compar- isons between the damage and plastic damage approaches have been carried out by Jason [16] . They show that the intro- duction of plasticity does not change the failure mode of the structure compared to usual results with a simple damage model because in tension dominated situations the damage part of the model is the essential ingredient of the constitutive response. The plastic damage model has the same modelling capabilities as the damage model in a type of structural ana- lysis where it is established that the second performs very well. In the case of regular meshes, it is possible to adjust the softening response of the model to fit experimental data on structural applications (provided the discretisation is such that mesh alignment is consistent with the crack path). In a more general context, however, regularisation techniques should be included in the formulation to avoid numerical problems [37,34,38,1] .
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Damage model for FRP-confined concrete columns under cyclic loading

Damage model for FRP-confined concrete columns under cyclic loading

This paper presents a numerical strategy to model slender FRP- confined concrete structures, such as columns, based on a multifiber beam description to reproduce the 3D behavior and a 1D (global) stress–strain concrete constitutive model suitable for cycling load- ings in order to simulate the nonlinear behavior at the fiber level. The proposed model deals with internal (due to TSR) and external (due to FRP) confinement, and considers the crack opening-and-clo- sure mechanism. It was inspired by the La Borderie’s cyclic model for (unconfined) concrete based on damage mechanics and Eid and Paul- tre’s confined-concrete model based on experimental studies. Vali- dation is provided using experimental results on RC-retrofitted columns (8 isolated columns and 1 bridge-pier mockup) subjected to cyclic and pseudo-dynamic loadings. Numerical computations were performed with multifiber Timoshenko beam elements, intro- duced in the finite-element code FEDEASLab (a MATLAB toolbox). ⇑ Corresponding author. Present address: Université Paris-Est, IFSTTAR, SOA,
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Elastic-plastic ductile damage model based on strain-rate plastic potential

Elastic-plastic ductile damage model based on strain-rate plastic potential

Department of Mechanical and Aerospace Engineering, University of Florida, REEF, 1350 N. Poquito Rd, Shalimar, FL 32579, USA. ABSTRACT Modeling of ductile damage is generally done using analytical potentials, which are expressed in the stress space. In this paper, for the first time it is shown that strain rate potentials which are exact conjugate of the stress-based potentials can be instead used to model the dilatational response of porous polycrystals. A new integration algorithm is also developed. It is to be noted that a strain-rate based formulation is most appropriate when the plastic flow of the matrix is described by a criterion that involves dependence on all stress invariants. In such cases, although a strain-rate potential is known, the stress-based potential cannot be obtained explicitly. While the proposed framework based on strain-rate potentials is general, for comparison purposes in this work we present an illustration of the approach for the case of a porous solid with von Mises matrix containing randomly distributed spherical cavities. Comparison between simulations using the strain-rate based approach and the classical stress- based Gurson’s criterion in uniaxial tension is presented. These results show that the model based on a strain-rate potential predicts the dilatational response with the same level of accuracy.
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On the influence of the steel-concrete bond model for the simulation of reinforced concrete structures using damage mechanics

On the influence of the steel-concrete bond model for the simulation of reinforced concrete structures using damage mechanics

Key words: concrete, steel-concrete bond, structures, damage, simulation 1. Introduction Steel is widely used in civil engineering applications to strengthen concrete in tension. These so-called reinforced concrete structures, which present a more ductile behavior compared to plain concrete, may nevertheless be subjected to cracking. In this case, when a crack initiates, stresses in concrete drop to zero and the loading is totally supported by the reinforcements. They are then responsible for stress transfer around the crack from steel to concrete. This progressive redistribution, which can be easily demonstrated in the case of a reinforced concrete tie, is directly influenced by the bond properties [1]. That is why the influence of the steel-concrete bond has to be carefully studied, especially when the crack properties, which are directly related to this stress distribution, play a key role in the structural functions (failure mode, tightness…).
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Impulsive zone model predictive control for rendezvous hovering phases

Impulsive zone model predictive control for rendezvous hovering phases

∆ν = 30 ◦ Fig. 3: Consumption for N = 3 over the first 3 periods parametrization of the relative motion allows to character- ize the periodic orbits as the set of equilibrium points. In such context, the predictive controller is shown to be able to steer the system closer and closer to the target set by means of a single feasible control action. The main controller characteristics such as the recursive feasibility and the stability are then deduced from this fact. Furthermore, the controller has a significantly enlarged domain of attraction (given by C N ( D s ), instead of C N (S D ), which is the usual case) without using artificial variables (as it is done in the so called MPC for tracking [32]). Simulation results show that the proposed controller exhibits good performances by comparison to other MPC and Hybrid control strategies. Future works include a further study and characterization of the domain of attraction but also robust analysis with respect to control mis-execution errors.
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Behaviour of EMP under shear loadings

Behaviour of EMP under shear loadings

1, Chemin des Chevreuils, B-4000 Liège A.Plumier@ulg.ac.be Expanded Metal, Cyclic behaviour, Cyclic Tests, Hysterical Loops. Experimental and theoretical study of expanded metal panels (EMP) has shown that they are useful for seismically retrofitting reinforced concrete moment resisting frames (RC-MRF). Although this only used for non-structural applications. There is no guidance existing to help the engineers determine the mechanical properties or to indicate in With the aims at providing quantitative data for ese purposes and at introducing a simplified model of EMP working in shear, description and comparison of the results of 22 monotonic and cyclic experiments of 4 profiles of EMP in small and large scale is presented. Numerical approach with FINELG, a nonlinear finite element code developed at University of Liege, is used to calibrate and simulate the tests. A good correlation between tests and
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Development of a Novel Damage Model for Concrete Subjected to High Temperature and Constraint

Development of a Novel Damage Model for Concrete Subjected to High Temperature and Constraint

ABSTRACT When subjected to high temperatures, concrete exhibits a load-dependent thermal strain known as load induced thermal strain (LITS) or transient thermal creep (TTC). LITS phenomena can be important in pre- stressed concrete structures, as its evolution under transient thermal conditions can potentially lead to both loss in pre-stress and residual tensile stress development. Hence, such structures may evolve damage and loss of rigidity when subjected to high temperature thermal loading cycles. Whilst LITS models have recently become available in the public domain, they cannot capture damage from mechanical loading. Indeed, whilst most relevant damage models partially capture damage mechanisms of concrete, they do not adequately capture anisotropy and inelasticity in addition to the unilateral effect exhibited by concrete, i.e. the Mazars damage model. However, the recently developed Fichant-La Borderie (FLB) damage model has shown that these additional effects can be captured making the FLB model suitable to capture mechanical damage and LITS effects. In this paper, a method for coupling a LITS model with a FLB model is proposed. Numerical studies demonstrate that this model has the potential to enable accurate assessment of structural damage from transient thermal events, such as fire.
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