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Stochastic discrete modeling of progressive damage of concrete structures
Kučera, Michal ; Sadílek, Václav (referee) ; Vořechovský, Miroslav (advisor)
The work focuses on the use of deterministic discrete modeling with representation of spatial randomness in material parameters to simulate a series of experimental tests of concrete specimens in the shape of a dog bone, loaded in excentric uniaxial tension. The main focus is on the influence of the size of the structure on its mechanical properties, especially nominal strength (Size effect). The specimens are modeled as a plane stress problem using available discrete computational methods.
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Comparison of localization limiters for strain-softening
Květoň, Josef ; Vořechovský, Miroslav (referee) ; Eliáš, Jan (advisor)
It is well known, that simulation of crack propagation using the finite element method is dependent on mesh discretization. The thesis compares two approaches, that are designed to reduce the mesh influence: (I) the crack band model and (II) the nonlocal model. These localization limiters are applied to simulate three-point-bent beam with and without notch. The model of the beam is made with several variants of mesh discretization differing in finite element size and inclination. Performance of both localization limiters is discussed.
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Simulation of Fracture Tests in Civil Engineering
Bordovský, Gabriel ; Vaverka, Filip (referee) ; Jaroš, Jiří (advisor)
In this thesis, a program for fracture test in civil engineering has been optimized. The simulation is used for a validation of the fracture characteristics for blocks of construct material used for historic buildings reconstructure. This thesis illustrates the possibilities of an effective usage of the processor’s potential without the loss of the output quality. The individual parts of the simulation are analyzed and this thesis proposes for the critical sections some possible optimizations such as vectorization or parallel processing. The techniques used in this thesis may be used on similar computing problems and help shorten the required runtime. The prototype of the simulation was able to process the simulation in 7.7 hours. Optimized version is capable to process the same simulation in 2.1 hours on one core or 21 minutes on eight cores. The parallel optimized version is 21 times faster than the prototype.
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Stochastic discrete modeling of progressive damage in concrete structures
Kučera, Michal ; Sadílek, Václav (referee) ; Vořechovský, Miroslav (advisor)
The work focuses on the statistical strength of structures made of quasi-brittle ma- terials, specifically concrete. Special attention is paid to the influence of the size of the structure on strength and on the entire process of material failure during loading. The mechanics of these processes are modeled using discrete models, and these models are also considered in a probabilistic variant with spatially variable material parameters. Spatial variability is then modeled using random fields. The work clarifies the effect of diffuse damage in the volume of the structure before reaching the maximum load on the further course of dissipative processes, especially on the shape of the fracture process zone and subsequently on its interaction with the random variability of material parame- ters in eccentrically drawn dogbone-shaped bodies. In addition to the tools of stochastic computer fracture mechanics, an analytical model based on averaging and subsequent analysis of the minimum of the random field is presented
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Stochastic discrete modeling of progressive damage of concrete structures
Kučera, Michal ; Sadílek, Václav (referee) ; Vořechovský, Miroslav (advisor)
The work focuses on the use of deterministic discrete modeling with representation of spatial randomness in material parameters to simulate a series of experimental tests of concrete specimens in the shape of a dog bone, loaded in excentric uniaxial tension. The main focus is on the influence of the size of the structure on its mechanical properties, especially nominal strength (Size effect). The specimens are modeled as a plane stress problem using available discrete computational methods.
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Simulation of Fracture Tests in Civil Engineering
Bordovský, Gabriel ; Vaverka, Filip (referee) ; Jaroš, Jiří (advisor)
In this thesis, a program for fracture test in civil engineering has been optimized. The simulation is used for a validation of the fracture characteristics for blocks of construct material used for historic buildings reconstructure. This thesis illustrates the possibilities of an effective usage of the processor’s potential without the loss of the output quality. The individual parts of the simulation are analyzed and this thesis proposes for the critical sections some possible optimizations such as vectorization or parallel processing. The techniques used in this thesis may be used on similar computing problems and help shorten the required runtime. The prototype of the simulation was able to process the simulation in 7.7 hours. Optimized version is capable to process the same simulation in 2.1 hours on one core or 21 minutes on eight cores. The parallel optimized version is 21 times faster than the prototype.
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Comparison of localization limiters for strain-softening
Květoň, Josef ; Vořechovský, Miroslav (referee) ; Eliáš, Jan (advisor)
It is well known, that simulation of crack propagation using the finite element method is dependent on mesh discretization. The thesis compares two approaches, that are designed to reduce the mesh influence: (I) the crack band model and (II) the nonlocal model. These localization limiters are applied to simulate three-point-bent beam with and without notch. The model of the beam is made with several variants of mesh discretization differing in finite element size and inclination. Performance of both localization limiters is discussed.
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Influence of stress concentrator geometry on fracture parameters values of quasi-brittle materials
Frantík, P. ; Keršner, Z. ; Klusák, Jan ; Řoutil, L. ; Seitl, Stanislav ; Veselý, V.
To assess the reliability of building structures, values of fracture mechanical properties of their materials have to be known. In the case of cement-based composite types the basic parameters are ascertained on the basis of evaluation of the response of specimens conducted to a test in a suitable testing configuration. Three-point bending specimens with a central starting notch are the most frequently used specimens for laboratory testing. The influence of the stress concentrator – starting central edge notch – in a three point bend specimen on the resulting values of fracture toughness was studied in author’s papers: a crack initiation at the notch tip was numerically simulated. It was shown that the values of fracture toughness obtained for specimens with larger widths of starting notch can be overestimated.
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