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Complex evaluation of brittleness of selected building composites
Machačová, Denisa ; Veselý, Václav (referee) ; Keršner, Zbyněk (advisor)
Specified topic of the thesis is a multilevel evaluation of brittleness of selected building composites. The work deals with the opinions of fracture parameters of test specimens of lightweight and ordinary concrete. Specimens further differed fibres content in concrete mixtures, their type and length. The work is divided into two parts, theoretical and practical. The theoretical part conceives composite materials and introduction to fracture mechanics. The practical part describes the different steps for fracture-mechanical parameters evaluation using StiCrack and Excel Visual Basic software. The main part of the work is to evaluate the brittleness of different test specimens, taking into account the type of concrete mix and type of fibres.
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Numerical analysis of selected silicate based composites shrinkage
Drbušková, Magdaléna ; Vlk, Zbyněk (referee) ; Keršner, Zbyněk (advisor)
The thesis is divided into two main parts. In the first theoretical part is described the problems of shrinking including a comparison of Czech standard and Model Code 2010, Vol. 1. The second practical part of the master`s thesis is focused on the numerical analysis shrinkage primarily on the initial stage of this process. The experimentally obtained data are set approximations of the relative deformation using ShrCeC. Subsequently the numerical simulation of shrinkage of selected silicate specimens using a computer applications SpatiDist and FyDiK 2D. The real test specimens are modelled as two-component composite consisting of cement paste and aggregates. The result is a parametric study takes into account the influence of type and size of grain aggregate.
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Physical Discretization Modelling of Shrinkage
Bedáň, Jan ; Keršner, Zbyněk (referee) ; Frantík, Petr (advisor)
The aim of this thesis is design and programming of a numerical model of shrinkage of cement composites using physical discretization and solved by parallel processing. Introduction is about the shrinkage of cement composites and explanation of terms, which are included in this thesis. The main part deals with programming of the output model, the procedure of its creation and the results of simulations.
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Evaluation of fracture tests of selected concrete specimens
Součková, Markéta ; Lehký, David (referee) ; Keršner, Zbyněk (advisor)
This bachelor thesis deals with evaluation of fracture tests of selected concrete specimens. It is divided into two parts: theoretical and practical. The theoretical section describes fracture parameters, three point bending test and effective crack model. It explains evaluation process of the expriments step by step, too. The practical part contains charts with the resulting values of fracture parameters. The StiCrack software was used for analysis of fracture tests. The result of this thesis is comparison of influence the thength classes of concrete, age of specimens and place of ripen on the values of fracture parameters.
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Modelling of Free Beam Loaded by Follower Load
Mašek, Jan ; Keršner, Zbyněk (referee) ; Frantík, Petr (advisor)
The aim of the presented thesis is to create a non-linear dynamical model of a free rod loaded by a follower force. The model is inspired by a slender flexible missile loaded by an end thrust. Because of the nature of the problem, the model has to be capable of large deflections. Another requirements on the model are to implement material the damping and the damping due to the interaction of the model with a surrounding medium and the influence of gravitational field. In the future, the model will be used for examination of the post-critical behavior of such construction. Therefore low computational demands of the simulation are required. The derived formulation of the numerical model will be implemented using the Java programming language. For observation of the simulation process and for monitoring of the state variables, an appropriate graphic interface will be created. The accuracy of the derived model will be verified by the comparison of selected values to the analytical solution.
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Numerical support for analysis of the fatigue behavior of cement based composites
Viszlay, Viliam ; Keršner, Zbyněk (referee) ; Seitl, Stanislav (advisor)
This thesis is focused on numerical analysis of fracture mechanics parameters in modified compact tension (CT) test. This CT test appears to be a suitable alternative to classic compact tension test for using for testing of quasi-brittle materials. The classic compact tension test is commonly used for fatigue testing of metallic materials and the geometry of used specimens does not allow using this test for quasi-brittle materials like cement based composites. The modified version of this test with cylindrical shape of the specimen allows us to test fatigue behaviour of quasi-brittle materials. In this thesis the influence of the modification of classic CT test on fracture mechanic parameters are determinated. In the next step, the influence of the position of steel bars (the position of loading force) on fracture mechanic parameters are evaluated. Obtained values are presented in graphs and calibration polynomials for each geometry are proposed.
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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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Study of influence of input parameters for the numerical modeling of the compression test
Polách, Marek ; Keršner, Zbyněk (referee) ; Lehký, David (advisor)
The thesis analyses influence of input parametres of the 3D Non Linear Cementitious 2 material model for the numerical modeling of compression test performed in ATENA 2D and ATENA 3D software. The aim is to identify parametres with considerable influence and subsequently replicate the load-deflection curve obtained from laboratory compression test by numerical modeling. The effects of selected model and material model settings are studied on three kind of models in total. As tools for analyzing the effects, deterministic and statistic sensitivity analyses were chosen. Parametres with significant influence will be highlighted and added to the group of parametres obtained from numerical modeling of three-point bending test. This will create a set of parametres of considerable influence when it comes to modeling advanced structures with different types of stresses.
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