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Miguel Cervera - One of the best experts on this subject based on the ideXlab platform.
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a novel positive negative projection in energy norm for the damage modeling of quasi brittle solids
International Journal of Solids and Structures, 2018Co-Authors: Jianying Wu, Miguel CerveraAbstract:Abstract The asymmetric tensile/compressive material behavior and microcracks closure-reopening (MCR) effects exhibited by quasi-brittle solids are of significant importance to the nonlinear responses of engineering structures under cyclic loading, e.g., earthquake excitations. Based on our previous work (Cervera et al., 1995; Faria et al., 1998; Wu et al., 2006) this work addresses a novel thermodynamically consistent unilateral damage model for concrete. In particular, the positive/negative projection (PNP) of the Effective Stress Tensor and the additive bi-scalar damage constitutive relation are maintained owing to the conceptual simplicity and computational efficiency. It is found that the classical PNP widely adopted in the literature is not optimal for this damage model, since the resulting stiffness is not always of major symmetry. Consequently, a well-defined free energy potential does not exist in general cases and the model cannot be cast into the framework of thermodynamics with internal variables. Furthermore, the damage induced anisotropy cannot be captured, exhibiting excessive lateral deformations under uniaxial tension. To overcome the above issues, a novel PNP, variationally interpreted as the closest point projection of the Effective Stress in energy norm, is proposed with closed-form solution. With the novel PNP, the secant stiffness Tensor of the proposed unilateral damage model always possesses major symmetry and exhibits orthotropic behavior under uniaxial tension and mixed tension/compression. The corresponding thermodynamics framework is then given, resulting in an energy release rate based rounded-Rankine type damage criterion appropriate for tensile failure in quasi-brittle solids. Several numerical examples of single-point verifications and benchmark tests are presented. It is demonstrated that the proposed model is capable of characterizing localized failure of concrete under proportional and non-proportional static loading, as well as the MCR effects under seismic cyclic loading.
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A novel positive/negative projection in energy norm for the damage modeling of quasi-brittle solids
International Journal of Solids and Structures, 2018Co-Authors: Jianying Wu, Miguel CerveraAbstract:Abstract The asymmetric tensile/compressive material behavior and microcracks closure-reopening (MCR) effects exhibited by quasi-brittle solids are of significant importance to the nonlinear responses of engineering structures under cyclic loading, e.g., earthquake excitations. Based on our previous work (Cervera et al., 1995; Faria et al., 1998; Wu et al., 2006) this work addresses a novel thermodynamically consistent unilateral damage model for concrete. In particular, the positive/negative projection (PNP) of the Effective Stress Tensor and the additive bi-scalar damage constitutive relation are maintained owing to the conceptual simplicity and computational efficiency. It is found that the classical PNP widely adopted in the literature is not optimal for this damage model, since the resulting stiffness is not always of major symmetry. Consequently, a well-defined free energy potential does not exist in general cases and the model cannot be cast into the framework of thermodynamics with internal variables. Furthermore, the damage induced anisotropy cannot be captured, exhibiting excessive lateral deformations under uniaxial tension. To overcome the above issues, a novel PNP, variationally interpreted as the closest point projection of the Effective Stress in energy norm, is proposed with closed-form solution. With the novel PNP, the secant stiffness Tensor of the proposed unilateral damage model always possesses major symmetry and exhibits orthotropic behavior under uniaxial tension and mixed tension/compression. The corresponding thermodynamics framework is then given, resulting in an energy release rate based rounded-Rankine type damage criterion appropriate for tensile failure in quasi-brittle solids. Several numerical examples of single-point verifications and benchmark tests are presented. It is demonstrated that the proposed model is capable of characterizing localized failure of concrete under proportional and non-proportional static loading, as well as the MCR effects under seismic cyclic loading.
Jeanfrancois Molinari - One of the best experts on this subject based on the ideXlab platform.
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multi scale modelling of concrete structures affected by alkali silica reaction coupling the mesoscopic damage evolution and the macroscopic concrete deterioration
International Journal of Solids and Structures, 2020Co-Authors: Emil R Gallyamov, Aurelia Isabel Cuba Ramos, Mauro Corrado, Roozbeh Rezakhani, Jeanfrancois MolinariAbstract:Abstract A finite-element approach based on the first-order FE2 homogenisation technique is formulated to analyse the alkali-silica reaction-induced damage in concrete structures, by linking the concrete degradation at the macro-scale to the reaction extent at the meso-scale. At the meso-scale level, concrete is considered as a heterogeneous material consisting of aggregates embedded in a mortar matrix. The mechanical effects of the Alkali-Silica Reaction (ASR) are modelled through the application of temperature-dependent eigenstrains in several localised spots inside the aggregates, and the mechanical degradation of concrete is modelled using continuous damage model, which is capable of reproducing the complex ASR crack networks. Then, the Effective stiffness Tensor and the Effective Stress Tensor for each macroscopic finite element are computed by homogenising the mechanical response of the corresponding representative volume element (RVE). Convergence between macro- and meso-scales is achieved via an iterative procedure. A 2D model of an ASR laboratory specimen is analysed as a proof of concept. The model is able to account for the loading applied at the macro-scale and the ASR-product expansion at the meso-scale. The results demonstrate that the macroscopic Stress state influences the orientation of damage inside the underlying RVEs. The Effective stiffness becomes anisotropic in cases where damage is aligned inside the RVE.
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multi scale modelling of concrete structures affected by alkali silica reaction coupling the mesoscopic damage evolution and the macroscopic concrete deterioration
arXiv: Computational Engineering Finance and Science, 2020Co-Authors: Emil R Gallyamov, Aurelia Isabel Cuba Ramos, Mauro Corrado, Roozbeh Rezakhani, Jeanfrancois MolinariAbstract:A finite-element approach based on the first-order FE 2 homogenisation technique is formulated to analyse the alkali-silica reaction-induced damage in concrete structures, by linking the concrete degradation at the macro-scale to the reaction extent at the meso-scale. At the meso-scale level, concrete is considered as a heterogeneous material consisting of aggregates embedded in a mortar matrix. The mechanical effects of the Alkali-Silica Reaction (ASR) are modelled through the application of temperature-dependent eigenstrains in several localised spots inside the aggregates and the mechanical degradation of concrete is modelled using continuous damage model, which is capable of reproducing the complex ASR crack networks. Then, the Effective stiffness Tensor and the Effective Stress Tensor for each macroscopic finite element are computed by homogenising the mechanical response of the corresponding representative volume element (RVE), thus avoiding the use of phenomenological constitutive laws at the macro-scale. Convergence between macro- and meso-scales is achieved via an iterative procedure. A 2D model of an ASR laboratory specimen is analysed as a proof of concept. The model is able to account for the loading applied at the macro-scale and the ASR-product expansion at the meso-scale. The results demonstrate that the macroscopic Stress state influences the orientation of damage inside the underlying RVEs. The Effective stiffness becomes anisotropic in cases where damage is aligned inside the RVE.
Jianying Wu - One of the best experts on this subject based on the ideXlab platform.
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a novel positive negative projection in energy norm for the damage modeling of quasi brittle solids
International Journal of Solids and Structures, 2018Co-Authors: Jianying Wu, Miguel CerveraAbstract:Abstract The asymmetric tensile/compressive material behavior and microcracks closure-reopening (MCR) effects exhibited by quasi-brittle solids are of significant importance to the nonlinear responses of engineering structures under cyclic loading, e.g., earthquake excitations. Based on our previous work (Cervera et al., 1995; Faria et al., 1998; Wu et al., 2006) this work addresses a novel thermodynamically consistent unilateral damage model for concrete. In particular, the positive/negative projection (PNP) of the Effective Stress Tensor and the additive bi-scalar damage constitutive relation are maintained owing to the conceptual simplicity and computational efficiency. It is found that the classical PNP widely adopted in the literature is not optimal for this damage model, since the resulting stiffness is not always of major symmetry. Consequently, a well-defined free energy potential does not exist in general cases and the model cannot be cast into the framework of thermodynamics with internal variables. Furthermore, the damage induced anisotropy cannot be captured, exhibiting excessive lateral deformations under uniaxial tension. To overcome the above issues, a novel PNP, variationally interpreted as the closest point projection of the Effective Stress in energy norm, is proposed with closed-form solution. With the novel PNP, the secant stiffness Tensor of the proposed unilateral damage model always possesses major symmetry and exhibits orthotropic behavior under uniaxial tension and mixed tension/compression. The corresponding thermodynamics framework is then given, resulting in an energy release rate based rounded-Rankine type damage criterion appropriate for tensile failure in quasi-brittle solids. Several numerical examples of single-point verifications and benchmark tests are presented. It is demonstrated that the proposed model is capable of characterizing localized failure of concrete under proportional and non-proportional static loading, as well as the MCR effects under seismic cyclic loading.
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A novel positive/negative projection in energy norm for the damage modeling of quasi-brittle solids
International Journal of Solids and Structures, 2018Co-Authors: Jianying Wu, Miguel CerveraAbstract:Abstract The asymmetric tensile/compressive material behavior and microcracks closure-reopening (MCR) effects exhibited by quasi-brittle solids are of significant importance to the nonlinear responses of engineering structures under cyclic loading, e.g., earthquake excitations. Based on our previous work (Cervera et al., 1995; Faria et al., 1998; Wu et al., 2006) this work addresses a novel thermodynamically consistent unilateral damage model for concrete. In particular, the positive/negative projection (PNP) of the Effective Stress Tensor and the additive bi-scalar damage constitutive relation are maintained owing to the conceptual simplicity and computational efficiency. It is found that the classical PNP widely adopted in the literature is not optimal for this damage model, since the resulting stiffness is not always of major symmetry. Consequently, a well-defined free energy potential does not exist in general cases and the model cannot be cast into the framework of thermodynamics with internal variables. Furthermore, the damage induced anisotropy cannot be captured, exhibiting excessive lateral deformations under uniaxial tension. To overcome the above issues, a novel PNP, variationally interpreted as the closest point projection of the Effective Stress in energy norm, is proposed with closed-form solution. With the novel PNP, the secant stiffness Tensor of the proposed unilateral damage model always possesses major symmetry and exhibits orthotropic behavior under uniaxial tension and mixed tension/compression. The corresponding thermodynamics framework is then given, resulting in an energy release rate based rounded-Rankine type damage criterion appropriate for tensile failure in quasi-brittle solids. Several numerical examples of single-point verifications and benchmark tests are presented. It is demonstrated that the proposed model is capable of characterizing localized failure of concrete under proportional and non-proportional static loading, as well as the MCR effects under seismic cyclic loading.
Emil R Gallyamov - One of the best experts on this subject based on the ideXlab platform.
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multi scale modelling of concrete structures affected by alkali silica reaction coupling the mesoscopic damage evolution and the macroscopic concrete deterioration
International Journal of Solids and Structures, 2020Co-Authors: Emil R Gallyamov, Aurelia Isabel Cuba Ramos, Mauro Corrado, Roozbeh Rezakhani, Jeanfrancois MolinariAbstract:Abstract A finite-element approach based on the first-order FE2 homogenisation technique is formulated to analyse the alkali-silica reaction-induced damage in concrete structures, by linking the concrete degradation at the macro-scale to the reaction extent at the meso-scale. At the meso-scale level, concrete is considered as a heterogeneous material consisting of aggregates embedded in a mortar matrix. The mechanical effects of the Alkali-Silica Reaction (ASR) are modelled through the application of temperature-dependent eigenstrains in several localised spots inside the aggregates, and the mechanical degradation of concrete is modelled using continuous damage model, which is capable of reproducing the complex ASR crack networks. Then, the Effective stiffness Tensor and the Effective Stress Tensor for each macroscopic finite element are computed by homogenising the mechanical response of the corresponding representative volume element (RVE). Convergence between macro- and meso-scales is achieved via an iterative procedure. A 2D model of an ASR laboratory specimen is analysed as a proof of concept. The model is able to account for the loading applied at the macro-scale and the ASR-product expansion at the meso-scale. The results demonstrate that the macroscopic Stress state influences the orientation of damage inside the underlying RVEs. The Effective stiffness becomes anisotropic in cases where damage is aligned inside the RVE.
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multi scale modelling of concrete structures affected by alkali silica reaction coupling the mesoscopic damage evolution and the macroscopic concrete deterioration
arXiv: Computational Engineering Finance and Science, 2020Co-Authors: Emil R Gallyamov, Aurelia Isabel Cuba Ramos, Mauro Corrado, Roozbeh Rezakhani, Jeanfrancois MolinariAbstract:A finite-element approach based on the first-order FE 2 homogenisation technique is formulated to analyse the alkali-silica reaction-induced damage in concrete structures, by linking the concrete degradation at the macro-scale to the reaction extent at the meso-scale. At the meso-scale level, concrete is considered as a heterogeneous material consisting of aggregates embedded in a mortar matrix. The mechanical effects of the Alkali-Silica Reaction (ASR) are modelled through the application of temperature-dependent eigenstrains in several localised spots inside the aggregates and the mechanical degradation of concrete is modelled using continuous damage model, which is capable of reproducing the complex ASR crack networks. Then, the Effective stiffness Tensor and the Effective Stress Tensor for each macroscopic finite element are computed by homogenising the mechanical response of the corresponding representative volume element (RVE), thus avoiding the use of phenomenological constitutive laws at the macro-scale. Convergence between macro- and meso-scales is achieved via an iterative procedure. A 2D model of an ASR laboratory specimen is analysed as a proof of concept. The model is able to account for the loading applied at the macro-scale and the ASR-product expansion at the meso-scale. The results demonstrate that the macroscopic Stress state influences the orientation of damage inside the underlying RVEs. The Effective stiffness becomes anisotropic in cases where damage is aligned inside the RVE.
Giuseppe Sciumè - One of the best experts on this subject based on the ideXlab platform.
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mechanistic modeling of vascular tumor growth an extension of biot s theory to hierarchical bi compartment porous medium systems
Acta Mechanica, 2021Co-Authors: Giuseppe SciumèAbstract:Existing continuum multiphase tumor growth models typically do not include microvasculature, or if present, this is modeled as a non-deformable network of vessels. Vasculature behavior and blood flow are usually non-coupled with the underlying tumor phenomenology from the mechanical viewpoint; hence, phenomena like vessel compression/occlusion modifying microcirculation and oxygen supply cannot be taken into account. Here, the tumor tissue is modeled as a reactive bi-compartment porous medium: the extracellular matrix constitutes the solid scaffold; blood flows in the vascular porosity, whereas the extravascular porous compartment is saturated by two cell phases and interstitial fluid (mixture of water and nutrient species). The pressure difference between blood and the extravascular overall pressure is sustained by vessel walls and drives shrinkage or dilatation of the vascular porosity. Model closure is achieved thanks to a consistent non-conventional definition of the Biot’s Effective Stress Tensor. Angiogenesis is modeled by introducing a vascularization state variable and accounting for tumor angiogenic factors and endothelial cells. Closure relationships and mass exchange terms related to vessel formation are detailed in a numerical example reproducing the principal features of angiogenesis. This example is preceded by a first pedagogical numerical study on one-dimensional bio-consolidation. Results demonstrate that the bi-compartment poromechanical model is fully coupled (the external loads impact fluid flow in both porous compartments) and that it can serve as a basis for further applications like modeling of drug delivery and tissue ulceration.
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mechanistic modeling of vascular tumor growth an extension of biot s theory to hierarchical bi compartment porous medium system
bioRxiv, 2020Co-Authors: Giuseppe SciumèAbstract:Existing continuum multiphase tumor growth models typically do not include microvasculature, or if present, this is modeled as non-deformable. Vasculature behavior and blood flow are usually non-coupled with the underlying tumor phenomenology from the mechanical viewpoint; hence, phenomena as vessel compression/occlusion modifying microcirculation and oxygen supply cannot be taken into account. The tumor tissue is here modeled as a reactive bi-compartment porous medium: the extracellular matrix constitutes the solid scaffold; blood is in the vascular porosity whereas the extra-vascular porous compartment is saturated by two cell phases and interstitial fluid (mixture of water and nutrient species). The pressure difference between blood and the extra-vascular overall pressure is sustained by vessel walls and drives shrinkage or dilatation of the vascular porosity. Model closure is achieved thanks to a consistent non-conventional definition of the Biots Effective Stress Tensor. Angiogenesis is modeled by introducing a vascularization state variable, and accounting for tumor angiogenic factors and endothelial cells. Closure relationships and mass exchange terms related to vessel formation are detailed in a numerical example reproducing the principal features of angiogenesis. This example is preceded by a first pedagogical numerical study on one-dimensional bio-consolidation. Results are exquisite to realize that the bi-compartment poromechanical model is fully coupled (the external loads impact fluid flow in both porous compartments) and to envision further applications as for instance modeling of drugs delivery and tissue ulceration.
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A viscoelastic Unitary Crack-Opening strain Tensor for crack width assessment in fractured concrete structures
Mechanics of Time-Dependent Materials, 2017Co-Authors: Giuseppe Sciumè, Farid BenboudjemaAbstract:A post-processing technique which allows computing crack width in concrete is proposed for a viscoelastic damage model. Concrete creep is modeled by means of a Kelvin–Voight cell while the damage model is that of Mazars in its local form. Due to the local damage approach, the constitutive model is regularized with respect to finite element mesh to avoid mesh dependency in the computed solution (regularization is based on fracture energy). The presented method is an extension to viscoelasticity of the approach proposed by Matallah et al. (Int. J. Numer. Anal. Methods Geomech. 34(15):1615–1633, 2010 ) for a purely elastic damage model. The viscoelastic Unitary Crack-Opening (UCO) strain Tensor is computed accounting for evolution with time of surplus of Stress related to damage; this Stress is obtained from decomposition of the Effective Stress Tensor. From UCO the normal crack width is then derived accounting for finite element characteristic length in the direction orthogonal to crack. This extension is quite natural and allows for accounting of creep impact on opening/closing of cracks in time dependent problems. A graphical interpretation of the viscoelastic UCO using Mohr’s circles is proposed and application cases together with a theoretical validation are presented to show physical consistency of computed viscoelastic UCO.
