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Study on Damage of Concrete

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Tutor: ZhaoJun
School: Henan University
Course: Detection Technology and Automation
Keywords: Concrete,Parallel truss model,3D damage model,The Ottosen this constitutive mode
CLC: TU528
Type: Master's thesis
Year:  2005
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Abstract:
Concrete in the role of external factors such as load, temperature, etc., will produce stress and strain, based on the concept of damage mechanics, the concrete will also damage occurs and generates a damage accumulation, resulting in the continuous cracking of the material properties, ultimately generating macro-cracks until destruction. This paper aims to establish the practical concrete damage model, and then concrete structures damaged. This article consists of four parts, namely: 1, concrete uniaxial stress - strain relationship-based model of parallel rods. From the perspective of fracture mechanics analysis of damage mechanism and softening behavior of concrete in uniaxial compression, bending of the the splitting crack surface instability is the main reason. Established a parallel bar system model to describe the mechanism which damage index. Several ordinary strength grade plain concrete and confined concrete to determine the specific parameters of the parallel bar system model and comparative analysis of different concrete pole distribution characteristics and generation mechanism. 2, based on Ottosen constitutive models for concrete 3D damage model. Proposed a concrete three-dimensional damage model based on the existing concrete constitutive model, the method no longer need to make a new parameter calibration, calculate the damage does not have to be the integral of the damage evolution equation. Constitutive model based on Ottosen the damage model, the damage parameter and Ottosen nonlinear index of different selection methods, the whole process of loading situations typical ratio of injury analysis, we found two different based on the stiffness degradation and based on the deformation capacity loss The damage description complementary, nonlinear index is calculated using a larger proportion of relatively simple and reasonable. Concrete damage model and the model with the classic Mazars damage model to do a comparative calculation. Sargin equation based on the transformation of concrete 3D damage model. Sargin equation based on the transformation of concrete dimensional damage model based on the inadequacies of the the constitutive model Ottosen damage model, the typical ratio of load situations the whole process of the damage calculation. Load - damage curve analysis found that the described method based on stiffness degradation of concrete damage and reasonable and suitable to describe three-dimensional load a variety of situations. The damage model is still isotropic damage model, three dimensional generally anisotropic damage, but a particle single damage index is still very useful. In addition, the model of three dimensional damage model based on Ottosen constitutive relation more in line with the test results, applies more broadly. 4, damage analysis of reinforced concrete beams. Sargin applications based on the transformation of the equation of concrete damage model for reinforced concrete simply supported beam under concentrated load and uniform load under the one-dimensional damage calculation. By comparison with the experimental phenomenon, indicating that the damage model are in good agreement with the actual situation in the one-dimensional case, simulation analysis provides a reference for the complexity of the concrete structural damage.
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