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Evaluation of Fracture Tests on Selected Building Material Specimens via Double-K Model
Havlíková, Ivana ; Králík,, Juraj (referee) ; Němeček,, Jiří (referee) ; Keršner, Zbyněk (advisor)
The purpose of dissertation is the analysis of the calculation of fracture parameters using Double-K fracture model for quasi-brittle specimens with the stress concentrator loaded by three-point bending or wedge splitting. To calculation of these parameters was used the developed DKFM_BUT software in Microsoft Excel application with using of Visual Basic programming language. Furthermore, the adequate shape functions and compliance functions were introduced for the selected wedge splitting test configurations. Main part of this dissertation is the series of comprehensively implemented and evaluated fracture experiments on specimens from advanced building materials, while the attention was paid to the analysis of experimental data. Finally, the selected results obtained using mentioned software support were presented and discussed.
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Shear bearing capacity of composite slabs
Holomek, Josef ; prof. Ing. Alois Materna, CSc., MBA (referee) ; Keršner, Zbyněk (referee) ; Bajer, Miroslav (advisor)
The subject of the submitted work is the experimental and theoretical investigation of composite slabs. The work also deals with creation of numerical models of composite slabs. The design of a new type of steel sheeting for composite slab according to nowadays standards requires full scale laboratory bending tests. An alternative to the bending tests are the small scale shear tests. The small scale shear tests as well as corresponding design methods have already been investigated by many researchers. Therefore several test arrangements and corresponding design methods can be found in literature but none of them is included in standards yet. The submitted thesis describes three of the alternative design methods: Slip- Block Test, Simplified Method and Built-up Bars. The test arrangement is proposed to be usable in all these methods. The small scale shear test have been performed in laboratory in several modifications. The results were used to calculate the bending resistance of the slab by the alternative design methods. The calculated bending resistances were mutually compared, compared with the performed bending tests resistances and the resistances by the methods described in Eurocode: m-k method and partial connection method. A sensitivity studies of the input parameters in alternative design methods are presented as well. The optimal design method for use in practice was searched and recommended based on the performed studies, accuracy and laboriousness of the methods. The shear tests were used also to measure longitudinal shear resistance of the additional shear anchors. The alternative design methods were used to predict bending resistance of the slab using these anchors and the results were compared. The numerical simulation of the composite action of the slab by the finite element methods is modelled in Atena software. The models serves to perform parametrical studies and to better understand of the behaviour of the slab in partial composite action.
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Three-dimensional Spring Networks and Their Applications
Štafa, Michal ; Brožovský, Jiří (referee) ; Keršner, Zbyněk (referee) ; Frantík, Petr (advisor)
The presented work highlights the remarkable potential of physical discretization – lattice model FyDiK in three-dimensional modelling of non-linear problems in structural mechanics. To achieve the objectives a software application, that implements the model FyDiK along with the 3D graphical user interface has been developed and thus is able to assemble a spring network model. Such a model was used for modelling the formation of cracks and fracture in the concrete specimens and also to model a plastic behaviour of steel I-beam. The calculations were performed by a massive parallelization on CUDA platform. In the first part the basic principles on which the work is based are introduced. Subsequently, a detailed description of individual parts of the model and the issue of parallelization by graphics cards are presented. In the next part the creation of the required software and improving of the model properties of mentioned materials are described. That is followed by evaluation of the achieved results with the comparison of other modelling software. The conclusion summarizes the achievements and suggestions for the further development possibilities of the presented method of modelling.
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Modeling of Elastic Mechanisms
Slaný, Jan ; Keršner, Zbyněk (referee) ; Frantík, Petr (advisor)
The thesis deals with constructing and solving a discrete mechanical model from the point of view of dynamics. As an example of a real-world problem which can be approximated in this way, the dynamical behaviour of a bow and arrow during loose have been chosen. In order to solve this particular type of model, a specialized piece of software has been developed. This method and software have been deployed to simulate shooting a straight bow of specific parametres. Two variants for the shape of the bowstaff have been evaluated.
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Basic features of aggregate-matrix-interface fracture of selected building composites
Vyhlídal, Michal ; Seitl, Stanislav (referee) ; Keršner, Zbyněk (advisor)
The aim of this work is to analyze the behavior of cement composite, depending on the features of ITZ. The first part of the thesis is theoretical and deals with the origin and features of ITZ, defines the basic relationships and concepts of continuum mechanics and linear elastic fracture mechanics and presents crack tips posibilities in the three-phase composite, including their short characterization. The second part is practical and describes creation of numerical model in the ANSYS software, presentation of partial results and compare of them. The result of this work is a comparison of the mean values of stress and amplitude of stress depending on the features of ITZ.
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Advanced evaluation of selected fracture tests of fibre reinforcement concrete specimens
Majda, Tomáš ; Frantík, Petr (referee) ; Keršner, Zbyněk (advisor)
The goal of this thesis was evaluation of extensive series of selected three point bending tests on fibre reinforced concrete specimens of ages 7, 28 and 126 days. First the measured data were adjusted by GTDiPS software. Than the assumed contribution of fibres in load--deflection diagram was approximated by regressive function. Contribution of matrix was calculated by deducting the approximated part from full diagram. Using StiCrack software the Young modulus, fracture toughness and fracture energy were calculated for both original and approximated diagram. All results were evaluated and tabled.
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Evaluation and simulations of fracture test of concrete specimens in selected configurations
Halfar, Petr ; Šimonová, Hana (referee) ; Keršner, Zbyněk (advisor)
This thesis deals with the evaluation of the selected fracture test configurations of concrete specimens. These configurations are the wedge splitting test or combinations of wedge splitting test and three point bending. The first part is theoretical and it describes the use of fracture mechanics on the quasi-brittle material - concrete. There are also described linear and nonlinear fracture theory, improvement process of fracture tests and also determination of the fracture parameters from the tests. The second part is practical and it describes editing of load-displacement diagrams by using GTDiPS application and then evaluation of the diagrams. The result of this work is comparison of the concrete fracture energy in each geometric variations of the tests.
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Advanced evaluation of fracture tests of selected rock specimens
Kubeš, Pavel ; Veselý, Václav (referee) ; Keršner, Zbyněk (advisor)
This bachelor's thesis deals with the advanced evaluation of fracture tests of selected rock (sandstone) specimens. The first part describes several fracture models/methods, fracture-mechanical parameters, process and configuration of the tests, used specimens and the procedure of data processing using the program GTDiPS. The second part contains neatly sorted evaluation of load-displacement diagrams. The results of the work are calculated fracture-mechanical parameters of various sandstones and their mutual comparison.
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