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Multi-parameter MTS and SED criterion applied on a crack in an alkali-activated concrete specimen under mixed-mode loading
Malíková, Lucie ; Miarka, Petr ; Šimonová, H.
The paper is devoted to an analysis of a crack propagation in a semi-circular concrete specimen under three-point bending. I+II mixed-mode loading is ensured via an inclined crack. Crack deflection angle is investigated by means of the generalized/multi-parameter form of the Maximum Tangential Stress (MTS) criterion and Strain Energy Density (SED) criterion as well as experimentally. The multi-parameter fracture mechanics concept applied in this work is based on the approximation of the crack-tip stress field by means of the Williams series expansion (WE). It has been proved that this approach can help to describe crack behavior in some kinds of materials better than the classical (one-parameter: stress intensity factor) fracture mechanics. This conclusion is discussed also in this paper.
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Analysis of concrete pipe using fracture-mechanical models
Bejček, Michal ; Šimonová, Hana (referee) ; Řoutil, Ladislav (advisor)
This bachelor thesis is focused on plain concrete pipe analysis in consideration of design problems. The introduction describes concrete pipe including imposed standards. The next part contains a summary of the calculation methods used nowadays. The thesis explores whether the fracture-mechanical calculation is sufficiently apt and therefore can be applied for the pipeline design. A number of pipe profile models was constructed and analysed for this purpose. The calculation based on the finite element method with applied crack band model was executed by software ATENA 2D. The crushing strength, which is compared to real tests data, is determined in models with altered input figures. The thesis also studies the negative effects on carrying capacity including material degradation.
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Determination of Fatigue Characteristics of Concrete Using Fracture-Mechanics Parameteres
Šimonová, Hana ; Králik,, Juraj (referee) ; Terzijski, Ivailo (referee) ; Bílek,, Vlastimil (referee) ; Keršner, Zbyněk (advisor)
The topic of this PhD. thesis is the issue of determining fatigue characteristics of selected cement-based composites. First, the history of fatigue of metal is mentioned, and some basic notions related to fatigue are clarified. The thesis also summarizes current research in the field of cement-based composites fatigue, and failure mechanisms of plain concrete during static and dynamic tests are described. Furthermore, the thesis deals with the evaluation of static and dynamic experiments’ results with extensive series of C30/37 and C45/55 class concrete specimens. In order to achieve relevant fatigue test evaluation which takes into account the age of the specimens, a new correction procedure of the data measured based on the approximation of the basic fracture-mechanics parameters of tested materials over time was suggested and verified. The annexes of this thesis present complete data obtained during static and dynamic experiments.
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Bend specimens: Numerical support in software ANSYS
Viszlay, Viliam ; Šimonová, Hana (referee) ; Seitl, Stanislav (advisor)
The aim of the thesis is the investigation of fracture-mechanics parameters on specimens made of quasi-brittle materials. The principles of two-parameter fracture mechanics are used. Couple of numerical simulations were done and their outputs are used for two main analysed specimen geometries. For simulations the finite element method software ANSYS is used. In the first part, the thesis focuses on bended specimens. The influence of different geometric parameters on fracture mechanics behaviour of cracked specimen is investigated. For model calibration the outputs of other authors are used. In the second part the specimens for modified compact-tension test (CT test) are analysed. Similar to the first part, the influence of geometric parameters of the specimen (in this case, the specimen size) on fracture mechanics parameters were investigated. The modified CT test was derived from CT test which is commonly used for metal materials testing as the suitable geometry for cement-based composite materials testing. The outputs of both parts are calibration polynomials, which are expressions obtained for different specimen geometries, giving the value of fracture mechanics parameter as the function of specimen geometry. As the example, calibration curves are used to obtain fracture toughness of tested material using the outputs from recent experiment.
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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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Analysis of selected silicate based composites volume changes
Kubeš, Pavel ; Šimonová, Hana (referee) ; Keršner, Zbyněk (advisor)
This diploma thesis deals with the analysis of volume changes of selected silicate based composites. The first part introduces the issue of volume changes of concrete, especially the shrinkage process, two selected models for shrinkage prediction, describes configuration and course of performed tests, as well as the processing of measured experimental data. The second part contains input data modified by the program GTDiPS and another calculated parameters. The result of the work is the evaluation of the influence of thermal dilation on the development of shrinkage of young concrete. Another output is the comparison of accuracy of the two selected prediction models to capture the course of measured shrinkage.
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Architectural study of the sacral object Brno - Líšeň / second stage
Simonova, Hanna ; Žalmanová, Petra (referee) ; Šindlar, Jiljí (advisor)
The main theme of the diploma is the design of a new Roman Catholic church and parish within the framework of the construction of a panel residential complex in Nový Líšeň in Brno. Due to the fact that Salesian children and youth workers came to the area in 1990, it became necessary to build a church and a Salesian youth center. This proposal is based on an analysis of the urban context. The church is surrounded by prefabricated houses next to a school, a health clinic, a shopping center, and a Salesian youth center in a gently sloping area facing south with the dominant Palava hills.
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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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MULTI-PARAMETER MTS AND SED CRITERION APPLIED ON A CRACK IN AN ALKALI-ACTIVATED CONCRETE SPECIMEN UNDER MIXED-MODE LOADING
Malíková, Lucie ; Miarka, Petr ; Simonová, H.
The paper is devoted to an analysis of a crack propagation in a semi-circular concrete specimen under three-point bending. I+II mixed-mode loading is ensured via an inclined crack. Crack deflection angle is investigated by means of the generalized/multi-parameter form of the Maximum Tangential Stress (MTS) criterion and Strain Energy Density (SED) criterion as well as experimentally. The multi-parameter fracture mechanics concept applied in this work is based on the approximation of the crack-tip stress field by means of the Williams series expansion (WE). It has been proved that this approach can help to describe crack behavior in some kinds of materials better than the classical (one-parameter: stress intensity factor) fracture mechanics. This conclusion is discussed also in this paper.
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