Research On The Crack Numerical Simulative Technique About The Steel Liner-Reinforced Concrete Penstocks Of The Three Gorges Hydroelectric Station

This paper main discussed the numerical simulative technique of the crack about reinforced concrete. And in this technique, the crack extending in some typical cases about the steel liner-reinforced concrete penstocks of the Three Gorges hydroelectric station is analyzed.As we all know that damage constitutional law of concrete is fit for solving mass little cracks situation, that fracture mechanics model is fit for solving only a few cracks situation, that separate crack model is only fit for dealing with those cracks whose locations is known firstly. But these situations don't reflect the crack characteristic of the steel liner-reinforced concrete penstocks of the Three Gorges. So, this paper adopts the smear crack model to simulate crack. The smear crack model can process the situation that the crack location isn't known first and can analyze the crack extending continuously without remeshing the grid. As the space structure of the steel liner-reinforced concrete penstocks of the Three Gorges is complicated, the two-dimension smear crack model is hard to reflect the real case. So, this paper establishes the smear crack model based on three- dimension. Specifically, according to the W-W five parameters failure theory, the fracture criterion of crack is established, and the state of crack (open or close) is judged by the values of the crack strain. Combining the two points, the predict-model about the failure of concrete material is established. This predict-model can predict 16 failure forms, and basing the different failure form predicted after crack, the stress-strain relationship matrix of concrete material is adjusted. That is, after crack, to simulate the crack-behavior of concrete, the previous stiffness matrix is substituted for by equivalent stiffness matrix. Because of the stiffness paralleled the crack direction becoming zero after crack, the whole stiffness matrix easily leads to morbidity. Considering this point, the crack element is preprocessed by multiplying a relaxation coefficient.In the same load case, we compare the result calculated from the crack model withthe result observed from structural model experiment, finding that the two results are coincident nearly which validates the reliability of the crack model. After that, in this crack model, the crack extending in asymmetric inner pressure case, releasing water case on burning sun and periodically variety case of outside temperature field are all calculated, and these results can be referenced for designer or researcher.Finally, the crack width computation is discussed. As the crack model can't calculate the crack width alone, this paper adopts the method of combining the crack model and the experiential formula of space between crack. Considering the uniformity factor is ignored in the experiential formula of space between crack, the formula of space between crack is modified so that it is fit for the real case.