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Using the identification of parameters of nonlinear material models for analysis of concrete structures
Král, Petr ; Králik, Juraj (referee) ; Maňas,, Pavel (referee) ; Hradil, Petr (advisor)
The presented thesis is focused on numerical modeling of concrete behavior (response) using nonlinear material models (constitutive relations) and on identification of input parameter values of these material models. Nowadays, there are a number of mathematically formulated constitutive relations intended not only to simulate the response of ductile or brittle materials, but also quasi-brittle materials. The constitutive relations for quasi-brittle materials are based on various theories (plasticity theory, the concept of damage mechanics, nonlinear fracture mechanics) and their complexity depends on the chosen type of solver. A general problem in the use of these constitutive relations is the need to define the values of their input parameters which these models usually include a very large number, and which often lack physical meaning, with their meaning being purely mathematical or experimental. This problem escalates with the increasing complexity of material models, which occurs in the transition from the formulation for the classic finite element method (FEM) to the formulation for the explicit FEM, and greatly complicates their practical application. The aim of this thesis is to present an approach how to deal with this problem for selected nonlinear constitutive relations. For this purpose, the thesis is divided into three main thematic parts. The first main part of the thesis is focused on the identification of input parameter values of the Continuous Surface Cap model. The purpose of this part is to first verify the effectivity and accuracy of the selected identification procedures. The following is the identification of model parameter values based on experimental data in order to adjust the derived calibration curves. In this part, the identification of input parameter values is demonstrated on both versions of the model. Data from the direct tensile test, compact tension test and four-point bending test of concrete are used. The second main part of th
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