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- Grassl, Peter, 1974, et al.
(författare)
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A damage-plasticity model for the dynamic failure of concrete
- 2011
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Ingår i: 8th International Conference on Structural Dynamics, Leuven, Belgium.
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Konferensbidrag (refereegranskat)abstract
- A constitutive model based on the combination of damage mechanics and plasticity is developed to analyse concretestructures subjected to dynamic loading. The aim is to obtain a model, which requires input parameters with clear physicalmeanings. The model should describe the important characteristics of concrete subjected to multiaxial and rate-depending loading.This is achieved by combining an effective stress based plasticity model with an isotropic damage model based on plastic andelastic strain measures. The model response in tension, uni-, bi- and tri-axial compression is compared to experimental results inthe literature.
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- Grassl, Peter, 1974, et al.
(författare)
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CDPM2: A damage-plasticity approach to modelling the failure of concrete
- 2013
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Ingår i: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683. ; 50:24, s. 3805-3816
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Tidskriftsartikel (refereegranskat)abstract
- A constitutive model based on the combination of damage mechanics and plasticity is developed to analyse the failure of concrete structures. The aim is to obtain a model, which describes the important characteristics of the failure process of concrete subjected to multiaxial loading. This is achieved by combining an effective stress based plasticity model with a damage model based on plastic and elastic strain measures. The model response in tension, uni-, bi- and triaxial compression is compared to experimental results. The model describes well the increase in strength and displacement capacity for increasing confinement levels. Furthermore, the model is applied to the structural analyses of tensile and compressive failure.
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- Grassl, Peter, 1974, et al.
(författare)
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Concrete in compression: A plasticity theory with a novel hardening law
- 2002
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Ingår i: International Journal of Solids and Structures. - 0020-7683. ; 39:20, s. 5205-5223
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with the modelling of the behaviour of plain concrete in triaxial compression using the theory of plasticity. The aim is to model the load resistance and the deformation capacity in uniaxial, biaxial and triaxial compression by means of few parameters, which can be determined easily.A novel hardening law based on a non-associated flow rule and the volumetric plastic strain as hardening parameter is combined with a yield surface proposed by Menetrey and William (1995). The novel hardening and softening law differs from a classic strain-hardening law, as instead of the length of the plastic strain vector only the volumetric component of the latter is used as a hardening parameter. Thus, the non-linearity of the plastic potential is utilized to describe the influence of multiaxial compression on the deformation capacity and no additional ductility measure is required.The implementation and calibration of the novel hardening law are discussed. The prediction of the model is compared to results of uniaxial, biaxial and triaxial compression tests. It is shown that with one set of calibration parameters a good prediction of the load resistance and the deformation capacity for all three types of compression tests can be achieved.
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- Grassl, Peter, 1974, et al.
(författare)
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On the Numerical Modelling of Bond for the Failure Analysis of Reinforced Concrete
- 2018
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Ingår i: Engineering Fracture Mechanics. - : Elsevier BV. - 0013-7944. ; 189, s. 13-26
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Tidskriftsartikel (refereegranskat)abstract
- The structural performance of reinforced concrete relies heavily on the bond between rein- forcement and concrete. In nonlinear finite element analyses, bond is either modelled by merged, also called perfect bond, or coincident with slip, also called bond-slip, approaches. Here, the performance of these two approaches for the modelling of failure of reinforced concrete was investigated using a damage-plasticity constitutive model in LS-DYNA. Firstly, the influence of element size on the response of tension-stiffening analyses with the two modelling approaches was investigated. Then, the results of the two approaches were compared for plain and fibre reinforced tension stiffening and a drop weight impact test. It was shown that only the coincident with slip approach provided mesh insensitive results. However, both approaches were capable of reproducing the overall response of the experiments in the form of load and displacements satisfactorily for the meshes used.
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- Grassl, Peter, 1974, et al.
(författare)
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Plastic model with non-local damage applied to concrete
- 2005
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Ingår i: International Journal for Numerical and Analytical Methods in Geomechanics. - : Wiley. - 0363-9061 .- 1096-9853. ; 30:1, s. 79-90
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Tidskriftsartikel (refereegranskat)abstract
- The present paper deals with a certain class of regularized models for concrete failure, combining plasticity with non-local damage. The plastic part is local and uses a yield condition formulated in the effective stress space. Softening is incorporated through the damage part of the model. Damage is considered as isotropic and linked to the evolution of plastic strain. The regularized version of the model is based on weighted spatial averaging of the damage-driving variable. Conditions for a mesh-independent description of the localized zone of inelastic strains are studied using one- and two-dimensional examples solved by simple non-local damage-plasticity models, in two dimensions with non-associated flow. Then, the framework is applied to an advanced model for concrete. Structural examples with tensile and compressive failure are presented. Copyright © 2005 John Wiley & Sons, Ltd.
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- Grassl, Peter, 1974
(författare)
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Plasticity and Damage Mechanics for Modeling Concrete Failure
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Concrete structures exhibit strongly non-linear and complex mechanical behavior. Hence, they are nowadays often analyzed by means of the finite element method, whereby a realistic description of the material behavior is decisive for the validity of the results. Concrete is a cohesive-frictional material, in which the stress transfer in many load cases is accomplished by frictional forces. Consequently, the three-dimensional stress-strain behavior is highly pressure-sensitive ranging from quasi-brittle behavior in tension to almost ductile response in high confined compression. Moreover, failure process in tension and low confined compression is accompanied by localization of deformations in the form of cracks and shear bands. In the present thesis, constitutive models based on plasticity and damage mechanics have been developed to describe the pressure-sensitive response and the localization of deformations. One of the advantages of stress-based plasticity models is the simple and direct calibration of the stress state. The yield surface corresponds at a certain stage of hardening to the strength envelope of concrete and has, therefore, a strong physical meaning. Moreover, the split into elastic and plastic strains is suitable to describe the irreversible deformations and volumetric expansion in compression. Nevertheless, the theory of plasticity fails to describe the degradation of stiffness associated with the failure process of concrete in tension and low confined compression. Damage mechanics models, on the other hand, are suitable to describe the stiffness degradation observed in experiments. Yet, damage models alone fail to describe the irreversible deformations and volumetric expansion associated with compressive failure. Combinations of plasticity and damage models are able to describe the main characteristics of concrete failure in tension and compression. The plastic-damage model developed in the present thesis consists of a stress-based plasticity model and a scalar damage model. The plasticity model is based on the effective stress to guarantee local uniqueness of the combined model. The isotropic damage model is based on the plastic strain, which permits a clear definition of the softening regime and thus simplifies the calibration. Moreover, the stress evolution approach of the damage model is explicit, which results in a computationally efficient combination of local plasticity and integral-type nonlocal damage for regularization of localized deformations.
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