A damage-plasticity model for the dynamic failure of concrete

A constitutive model based on the combination of damage mechanics and plasticity is developed to analyse concrete structures subjected to dynamic loading. The aim is to obtain a model, which requires input parameters with clear physical meanings. 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 and elastic strain measures. The model response in tension, uni-, bi- and tri-axial compression is compared to experimental results in the literature.Comment: Preprint. Submitted to Eurodyn 2011, 8th International Conference on Structural Dynamics, Leuven, Belgium, 201

CDPM2: 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.Comment: arXiv admin note: text overlap with arXiv:1103.128

Reinforcing tailor-made concrete structures: Alternatives and challenges

Recent advances in automated concrete production make it possible to produce geometrically complex concrete structures. The purpose of this paper is to review reinforcement alternatives suitable for such structures and to analyse the problems associated with the geometrical complexity, not only in the reinforcement itself, but also in design. A review of the literature on reinforcement alternatives and governing standards shows that conventional steel reinforcement load bearing structures cannot easily be set aside. Any deviation from the standard structural elements, e.g. beams, walls and slabs, introduces design problems for most structural engineers. Approaches to problems of this complex nature are discussed here. Further developments needed are indicated: being able to choose the reinforcement direction, and optimisation with regard to parameters other than the reinforcement amount, e.g. feasibility of production. Furthermore, the need for a rational design process is discussed and some key issues, such as software incompatibilities are raised

Bond between Reinforcement and Self-Compacting Steel-Fibre-Reinforced Concrete

In this study, pull-out tests of specimens with short embedment length and varying fibre content were carried out. The results showed no effect from the fibres on the bond-slip behaviour before peak load when normalized with respect to the compressive strength. After peak, the fibre reinforcement provided extra confinement, changing the failure mode from splitting to pull-out failure. The test results were used to calibrate a frictional bond model in non-linear finite element analyses. The model proved to yield results in good agreement with the experimental results regarding failure modes, load-slip relation and splitting strains on the surfaces of the pull-out specimens. The tests and analyses in combination confirmed that the fibre reinforcement neither disturbed nor improved the bond properties at the interface layer between reinforcement steel and concrete; i.e. the fibres only provided confinement to the surrounding structure

Fracture mechanics models for fatigue in concrete structures

This thesis deals with the application of fracture mechanics to model monotonic and cyclic loading of reinforced concrete structures. The main features of the work are: - Constitutive modelling based on fracture mechanics - Numerical studies of the models in various applications - Experimental studies to check the models and to determine material parameters The fracture mechanics models are formulated on a constitutive level. The models are based on energy considerations. Physically, the energy consumed in the fracture zones corresponds to microcracking of the material. The models apply directly to the description of two simple failure types in reinforced concrete: the tensile failure of plain concrete and the bond failure between steel and concrete. The fracture mechanics models are implemented in a finite element program (FEMP), and numerical studies are performed. As the constitutive relationships are non-linear, an incremental-iterative solution procedure is used. Three main examples are studied: the splitting of a concrete cube, the bending of a concrete bearn, and the pull-out of a smooth steel bar. Comparative experiments were conducted for all the three examples. Most of the constitutive material parameters can be obtained from standard tests. Two new parameters are introduced in order to model crackopening and crack-closing during cyclic loading. It is found that the presented theory can satisfactorily describe experimentally observed phenomena. Several phenomena, familiar to traditional fatique research, can also be recognized in the results of the numerical studies.Godkänd; 1983; 20070502 (ysko

Nonlinear FE Analyses of RC Bridge Frame Corners, Based on Fracture Mechanics

Reinforced concrete frame corners were analyzed using the nonlinear finite-element method and fracture mechanics. The objective of the study was to determine whether the reinforcement detailing in frame bridges could be simplified, with preserved structural safety, by splicing the reinforcement within the frame corner. A constitutive model for concrete, based on nonlinear fracture mechanics and plasticity, was used. An interface model was used to account for slip between the reinforcement and surrounding concrete. Analysis of previously tested frame specimens, with both spliced and unspliced corner reinforcement, was used to study the overall behavior of the frames; more detailed analysis of only the frame corner regions was used to study the influence of the reinforcement splices. The analyses were found to reflect the mechanical behavior of the specimens, and are in good agreement with the test results. The analysis results support, together with the test results, the idea that it would be feasible to splice all reinforcement in a portal frame bridge within the corner regions

Utmattningshållfasthet hos betongkonstruktioner

En översikt om utmattning av betongkonstruktioner att användas i civilingenjörsutbildningen på Chalmers tekniska högskola och Luleå tekniska universitetGodkänd; 1997; 20120814 (elfgren)</p