Modeling Material Failure in Concrete Structures (original) (raw)
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Modeling Material Failure in Concrete Structures under Cyclic Actions
Journal of Structural Engineering, 2004
A constitutive model devised for the analysis of concrete structures, and suitable for generic two-or three-dimensional applications, is presented and validated. For plain concrete a tension-compression distinguishing stress split is performed, and two scalar damage variables account for the degradation induced by the tensile and compressive stress components. As outcomes the model reproduces the stiffness recovery upon load reversal, and it captures the strength enhancement under multiaxial compression. Besides, the simple formulation as well as the extremely reduced number of parameters involved in the concrete model makes it quite suitable for the analysis of real structures, and constitutes a useful design tool. As regards to the nonlinear performance of the steel reinforcement, the explicit Giuffrè-Menegotto-Pinto model is adopted. Efficiency of the global model is illustrated via two seismic applications: one concerning an arch dam, and the other a six-floor reinforced concrete wall. The latter application is presented for validation purposes.
An analytical model, which can simulate the biaxial description of the nonlinear behavior of reinforced concrete structures, is introduced. The behavior of concrete is assumed orthotropic inside the ultimate failure surface and a compressive softening law of concrete is presented. The behavior of cracked concrete is simulated using the smeared crack model, which the tension stiffening effect based on a cracking criterion derived from the fracture mechanics principles is considered. A computer program is developed for analyzing the over and under-reinforced concrete beams. Several parameters such as the non-linearity proprieties, the cut off and tension stiffening models and shear retention factor are studied. The correlation between analytical and experimental results shows the validity of the proposed models and the significance of various effects. The global responses are evaluated to verify simultaneously the reliability of the proposed model and the performance of the numerical program.
Nonlinear analysis of reinforced concrete structures using a new constitutive model
Revue européenne des éléments finis, 2004
An analytical model, which can simulate the biaxial description of the nonlinear behavior of reinforced concrete structures, is introduced. The behavior of concrete is assumed orthotropic inside the ultimate failure surface and a compressive softening law of concrete is presented. The behavior of cracked concrete is simulated using the smeared crack model, which the tension stiffening effect based on a cracking criterion derived from the fracture mechanics principles is considered. A computer program is developed for analyzing the over and under-reinforced concrete beams. Several parameters such as the non-linearity proprieties, the cut off and tension stiffening models and shear retention factor are studied. The correlation between analytical and experimental results shows the validity of the proposed models and the significance of various effects. The global responses are evaluated to verify simultaneously the reliability of the proposed model and the performance of the numerical program.
New Tension-Compression Damage Model for Complex Analysis of Concrete Structures
Journal of Engineering Mechanics, 2016
A new damage model, based on continuum damage mechanics and simulating the opening, closing and reopening of cracks in concrete using only one surface of discontinuity, is proposed in this article. The model complies with the thermodynamics principles of non-reversible, isothermal and adiabatic processes. Two scalar internal variables have been defined: a tensile damage variable d + and a compressive damage variable d − ; the threshold of damage is controlled by only one surface of discontinuity and a new parameter that controls the damage variable which should be activated. This new parameter represents the ratio of tensile stress to compressive stress in the damaged material. The continuity of response under complex loads, which is one of the aims of this work, is ensured. An adequate response under different types of loads leads to the conclusion that the proposed model provides a powerful tool to numerically analyze reinforced concrete structures. Validation and illustrative examples are included in the article.
The paper presents an approach to constitutive modelling of concrete using damage mechanics and plasticity theory. The thermodynamic formulation, and parameter identification of a non-local coupled damage-plasticity model are presented in this study. The particular focus is the calibration of model parameters. It is shown that both the local parameters and the parameters governing the non-local interaction can be determined from experimental data reliably and consistently. A novel procedure is developed for parameter identification, using the separation of total dissipation energy into additive parts corresponding to different dissipation mechanisms. The relationship between the local and non-local parameters is also addressed, helping to obtain model responses consistent with the fracture energy of the material. The application of the model and the calibration procedure proposed in this study to the numerical failure analysis of concrete structures is illustrated through a series of real structural tests, showing both the performance of the model and the consistency of the proposed calibration procedure.
A numerical model for reinforced concrete structures
This paper describes a two-dimensional approach to model fracture of reinforced concrete structures under (increasing) static loading conditions. The first part is dedicated to the concrete material. The concrete is described in compression by a non-local isotropic damage constitutive law. In tension, a fictitious crack/crack band model is proposed. The influence of biaxial stress states is incorporated in the constitutive relations. In the second part a bond model is described. It accounts for different failure mechanisms, a pullout failure and a splitting failure. This approach is applied to prestressed concrete beams with different failure mechanisms. The numerical results are compared to experimental data and show good agreement.
A damage-plasticity approach to modelling the failure of concrete
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.
The upcoming need of concrete structures designed against impulsive and extreme load due to natural hazards, industrial accidents or terrorists attack requires analytical modeling capable of reproducing material behavior in this range of loading. When a concrete structure is submitted to an impact or an explosion loading, material may be submitted to high triaxial compression stresses as well as tensile stresses due to reflection of compressive waves on free surfaces. Furthermore, the water saturation degree in massive concrete structures may be nearly 100% at core whereas the material is dry on the skin. Thus, the impact response of a massive concrete wall may depend on the water saturation state in the material. This paper first presents some triaxial tests performed at a maximum confining pressure of 100 MPa on a concrete representative of a containment building of a nuclear power plant. Experimental results show the constitutive behavior and its dependence to the water saturation ratio of concrete specimens. The second part of this study aims at modeling these tests by means of the coupled PRM constitutive model. Although its robustness and effectiveness, this constitutive model did not allow to accurately reproduce the response of concrete specimens observed during the tests. The differences between experimental and numerical results can be explained by both the influence of the saturation state of concrete and the effect of deviatoric stresses which are not well taken into account into the PRM model. Some modifications of the PRM model were carried out; they allow improving the numerical prediction of concrete behavior under high triaxial stresses and various saturation states.
A 2D total strain based constitutive model for predicting the behaviors of concrete structures
International Journal of Engineering Science, 2006
We proposed a constitutive model for the two-dimensional analysis of concrete structures. The proposed model treats concrete as an orthotropic nonlinear material. The equivalent principal strain based approach allows the model to represent the mechanical behavior of concrete by using two equivalent uniaxial stress-strain relations. The biaxial behavior of concrete is described using the concept of current strength in a principal stress space. The fracture energy method is incorporated to solve the problem of mesh non-objectivity, and the concept of current fracture energy gives an improved description of the post-peak behavior of concrete. Secant-stiffness-based finite-element formulations are implemented in a smeared rotating crack fashion. Correlative studies using available experimental test results are presented to demonstrate the performance of the model at a structural level.