| Summary: | 博士 === 國立中央大學 === 土木工程研究所 === 92 === Nonlinear Discontinuous Deformation Analysis of Concrete Structures
ABSTRACT
In this thesis, a dual loading functions plasticity (DLFP) model that is capable to characterize the elastic-plastic behaviors of concrete material under various multi-axial stress state is proposed. The dilatation effect due to the formation of micro cracks and the shape change effect due to dislocation are taken into account by individual loading function to guide the plastic behavior of concrete. The hardening parameter of each loading function is determined based on series of worldwide-recognized experimental data. It is shown that the presented dual loading functions model can predict the plastic behavior of concrete material at various stress state. This incremental type model can be adapted into numerical code to simulate the irreversible behavior of concrete material during any loading –unloading process. The numerical algorithm for applying this DLFP model is also presented. Although associated flow rule is applied to individual loading function during the derivation, but it is proved that the overall format of the flow rule within this concrete plasticity model is non-associated.
We combine DLFP with Vector Form Intrinsic Finite Element, VFIFE, to analysis concrete structures. The procedure is mainly divided into two major parts by the formation of macro crack: the continuum behavior before macro crack forming and multi-bodies behavior after macro crack forming. The major work of the former is to establish a concrete constitutive relation. In this thesis, DLFP is adapted. The major work of the latter is to handle crack of concrete, which contains new nodes generation, detection of contact and contact force.
With such procedure, we analyze concrete structure under static and dynamic load. Comparing with uni-axial, bi-axial and tri-axial experiment data, DLFP represent a better choice of all the concrete models. This DLFP can handle cyclic behavior of concrete without difficulties. We also analyze a concrete structure that is under shear to verify the procedure of post failure behavior of concrete. Finally, we use this tool to analyze the concrete structure under dynamic loading. In qualitative analysis, we analyze the concrete slab under impact of low, medium and high velocities to verify the procedure. The results show the trends are admit with experiments though quantitative analysis still needs more efforts to put on.
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