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Initiation of stable crack propagation of selected building composites
Majtánová, Romana Viktória ; Veselý, Václav (referee) ; Keršner, Zbyněk (advisor)
The purpose of my bachelor’s thesis is study of the effects of fibres in normal-weight concrete and light-weight concrete. Specimens were prepared from concrete with polypropylene fibres FORTA FERRO of three different lengths – 19, 38 and 54 mm – and also reference concrete (without fibres) was prepared. This thesis contains gradual evaluation of fracture tests on specimens from mentioned materials. The used fracture test was a three–point bending fracture test on beams with a central notch. From the measured load–deflection in the middle of span and load–crack mouth opening displacement diagrams were determined values of modulus of elasticity, unstable fracture toughness, initiation part of fracture toughness and also load level for beginning of stable crack propagation composites. For determination was used „double–K“ fracture model. For illustration is described evaluation using the effective crack model.
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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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Fracture of selected building composites in the vicinity of aggregate-matrix-interface
Vyhlídal, Michal ; Malíková, Lucie (referee) ; Keršner, Zbyněk (advisor)
The interface between aggregate grains and matrix in cementitious composites is their weakest element. The topic is particularly significant in the case of high performance and high strength concrete technology for which the eliminination or reduction of these weak links are necessary. The aim of this thesis is to determine the influence of the interface on the fracture behaviour of the cementitious composites. The fracture experiments were performed for this purpose and were complemented by the nanoindentation’s results and scanning electron microscopy results. Numerical model was created in ANSYS software on the basis of these data and the fracture toughness values of the interface were evaluated by means of the generalized fracture mechanics principles. Conclusion of the thesis is proof that the interface properties have a significant influence on the fracture behaviour of cementitious composites.
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Mechanical fracture parameters of concrete after exposure to high temperatures
Bejček, Michal ; Keršner, Zbyněk (referee) ; Šimonová, Hana (advisor)
The diploma thesis is focused on the evaluation of mechanical fracture parameters of concrete after exposure to high temperatures. In the introductory theoretical part general principles of fracture mechanics with the concentration on a linear elastic fracture mechanics and non-linear fracture models for the concrete are summarized. The meaning of the three-point bending fracture test used for determination of fracture parameters is also explained. Further the influence of high temperatures on the partial components of concrete and general modeling of temperature loading is described. The practical part is concerned with the evaluation of fire experiments on the concrete panels including numerical simulations using GiD and ATENA software. The evaluation of data obtained from the three-point bending test carried out on specimens with initial stress concentrator taken from concrete panels is a main part of the diploma thesis. The values of modulus of elasticity, effective fracture toughness, work of fracture and fracture energy are determined from the measured F–d and F–CMOD diagrams after their proper corrections in the GTDiPS application. The evaluation of the selected mechanical fracture parameters was performed by StiCrack software using effective crack model and work of fracture method and DKFM_BUT software using the double-K fracture model. Finally, the attention is paid to the analysis of the obtained data.
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Fracture of selected building composites in the vicinity of aggregate-matrix-interface
Vyhlídal, Michal ; Malíková, Lucie (referee) ; Keršner, Zbyněk (advisor)
The interface between aggregate grains and matrix in cementitious composites is their weakest element. The topic is particularly significant in the case of high performance and high strength concrete technology for which the eliminination or reduction of these weak links are necessary. The aim of this thesis is to determine the influence of the interface on the fracture behaviour of the cementitious composites. The fracture experiments were performed for this purpose and were complemented by the nanoindentation’s results and scanning electron microscopy results. Numerical model was created in ANSYS software on the basis of these data and the fracture toughness values of the interface were evaluated by means of the generalized fracture mechanics principles. Conclusion of the thesis is proof that the interface properties have a significant influence on the fracture behaviour of cementitious composites.
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Mechanical fracture parameters of concrete after exposure to high temperatures
Bejček, Michal ; Keršner, Zbyněk (referee) ; Šimonová, Hana (advisor)
The diploma thesis is focused on the evaluation of mechanical fracture parameters of concrete after exposure to high temperatures. In the introductory theoretical part general principles of fracture mechanics with the concentration on a linear elastic fracture mechanics and non-linear fracture models for the concrete are summarized. The meaning of the three-point bending fracture test used for determination of fracture parameters is also explained. Further the influence of high temperatures on the partial components of concrete and general modeling of temperature loading is described. The practical part is concerned with the evaluation of fire experiments on the concrete panels including numerical simulations using GiD and ATENA software. The evaluation of data obtained from the three-point bending test carried out on specimens with initial stress concentrator taken from concrete panels is a main part of the diploma thesis. The values of modulus of elasticity, effective fracture toughness, work of fracture and fracture energy are determined from the measured F–d and F–CMOD diagrams after their proper corrections in the GTDiPS application. The evaluation of the selected mechanical fracture parameters was performed by StiCrack software using effective crack model and work of fracture method and DKFM_BUT software using the double-K fracture model. Finally, the attention is paid to the analysis of the obtained data.
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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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Initiation of stable crack propagation of selected building composites
Majtánová, Romana Viktória ; Veselý, Václav (referee) ; Keršner, Zbyněk (advisor)
The purpose of my bachelor’s thesis is study of the effects of fibres in normal-weight concrete and light-weight concrete. Specimens were prepared from concrete with polypropylene fibres FORTA FERRO of three different lengths – 19, 38 and 54 mm – and also reference concrete (without fibres) was prepared. This thesis contains gradual evaluation of fracture tests on specimens from mentioned materials. The used fracture test was a three–point bending fracture test on beams with a central notch. From the measured load–deflection in the middle of span and load–crack mouth opening displacement diagrams were determined values of modulus of elasticity, unstable fracture toughness, initiation part of fracture toughness and also load level for beginning of stable crack propagation composites. For determination was used „double–K“ fracture model. For illustration is described evaluation using the effective crack model.
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