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Measurement of Acoustic Parameters of Building Materials by Pseudorandom Sequence
Carbol, Ladislav ; Semerák,, Petr (referee) ; Koktavý, Bohumil (referee) ; Vydra,, Vítězslav (referee) ; Martinek, Jan (advisor)
The thesis deals with research of pulse compression of the acoustic signal in terms of applications in civil engineering. Based on the study and analysis of these methods, automated measuring equipment for non-destructive testing with pseudorandom sequence of maximum length and automated signal analysis, have been designed and implemented. In a single test cycle are obtained three parameters that characterize the linear and nonlinear behavior of the sample. A nonlinear parameter, Time of Flight of ultrasonic wave in the sample is further in the work compared with the conventional pulse measuring, and spectral analysis is compared with the method impact-echo. Functionality and optimization of the testing method was performed on a total of three sets of test pieces made of various building materials. The experiments proved simple result interpretation, and high sensitivity to structural damage associated with temperature loading. The results were correlated with conventional nondestructive methods and by destructive testing was measured change in compressive strength and flexural strength. This work also includes continual measurement of fundamental frequency influenced by moisture on a mortar sample. Use of pulse compression signal is in the civil engineering quite unusual. Only in recent years this topic is discussed in scientific articles with increasing frequency. Great potential lies in the association of three test methods into a single. Beneficial is high test speed and measurement reproducibility, but also theoretical possibility of testing massive test elements.
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Variační model pro vznik a šíření trhlin při zatížení teplotou
Beščec, Pavel ; Zeman, Jan (advisor) ; Seiner, Hanuš (referee)
Variational approach to brittle fracture based on the Griffith theory appears to be a vital tool for the modelling of initiation and propagation of cracks in brittle materials caused not only by the thermal loading. In the present work we familiarise the reader with the historical background of this scientific discipline, together with the regularised energy functional. The existence of a solution will be proved and the main advantages will be demonstrated on a numerical calculations. Also the difficulties and troubles of a model will be presented in order to deal with them in future work.
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Study of the properties of cement concrete at high temperatures
Žák, Michal ; Sitek,, Libor (referee) ; Bodnárová, Lenka (advisor)
This diploma thesis is focused on behavior of cement concrete at high temperatures. The theoretical part describes processes, which take place in concrete at thermal loading and effect of this thermal load to mechanical and physical properties of concrete. Also there was described recommendation for testing physical and mechanical of concrete at high temperatures according to RILEM TC. In experimental part mixes were made with greywacke aggregate, amphibolite aggregate and with the addition of polypropylene fibers or cellulose fibers. In these mixes was determined the effect of high temperatures on the density of concrete, compressive strength of concrete and thermal strain of concrete. Further there was tested addition of 2 kg/m3 polypropylene fibers to concrete with basalt aggregate and siliceous aggregate and influence of these fibers to density of concrete, compressive strength of concrete and dynamic modulus of elasticity.
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Durability of repair materials with higher fire resistance for concrete structures
Počekajlo, Václav ; Dohnálek,, Pavel (referee) ; Bydžovský, Jiří (advisor)
This dissertation deals with the study of durability and degradation repair mortars for reinforced concrete structures. In its theoretical part, there are the research findings on the behavior of repair mortars exposed to corrosive environments with different exposure time and selected high temperatures. Processes occurring in repair mortars during their loading at high temperatures or when exposed to chemically aggressive environments are described, We can find recipes designed for cementitious binder based with a specific replacement using slag or fly ash in its practical part. The object of the research was to determine the durability of the proposed repair mortars, and determine their suitability for use on concrete structures, which may be exposed to a synergistic effect of chemically aggressive environments with high temperatures simulating fire.
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Studying the behavior of concrete at high temperatures
Tillová, Jana ; Herka, Petr (referee) ; Bodnárová, Lenka (advisor)
This master‘s thesis is focused on the study of the behavior of cement concrete at high temperatures with a focus on monitoring the impact of aggregate and cement type. This work describes the processes in aggregates and cement matrix at high temperatures. The theoretical part describes the selestion of a suitable aggregate and cement for the surroundings with potential exposure to high temperatures. In the experimental part is given design of composition of a concrete with two types of aggregates and four cements. It has been suggested 8 recipes. Changes were observed densities, compressive strength and tensile strength in bending, calculate the velocity of propagation of waves with ultrasonic pulsed method. Also evaluated the appearance of the surface samples after thermal load – cracks on the surface and measure the maximum crack width.
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The concrete with a higher resistance to high temperatures
Mikulinec, David ; Hela,, Rudolf (referee) ; Bodnárová, Lenka (advisor)
The result of this master’s thesis is acquaintance with the issues of cement concrete resistance to high temperatures. This work describes the processes ongoing in the structure of concrete at extreme thermal loads and analysis of effects of high temperatures on the individual components of reinforced concrete structures is given, then influence of high temperatures and fire on the aggregates, matrix, reinforcement steel and the resulting changes in their properties. In the experimental part is given design of composition of concrete with a higher resistance to high temperatures and subsequent verification of the physico-mechanical properties of sample of concrete after exposure to temperatures at intervals of 200 ° C, 400 ° C, 600 ° C and 900 ° C. In individual recipes were observed changes of volume weight, changes of compressive strength and tensile strength flexural , tensile strength of surface layers and the occurrence of cracks and then were compared the results of thermally loaded and unloaded samples. The benefit in this issue is to evaluate the surface appearance of samples after heat load - study of area of crack and measurement of their width - was used according to the methodology's authors Xing, Hebert, Noumowe a Ledesert given in Cement and Concrete Research. This methodology allows to quantify changes of surface, after temperature load.
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Studying the behavior of cement concrete at high temperatures
Sovová, Kateřina ; Sitek,, Libor (referee) ; Bodnárová, Lenka (advisor)
Bachelor thesis is divided in two parts, theoretical and practical. In theoretical part are listed behaviour of cementious concrete at high temperatures and knowledge from particular construction, that was damaged by fire. There is given procedure of diagnostics for collected speciments of fire-damaged construction. In named analysis belong the carbonation depth through phenolphthalein solution and test of compressive strenght according DIN EN 13791 2008-05. In this study are demostrated results of tests, that were made on materials exposed to high temperatures. Result of constructions analysis is evaluation of economical reapairing works for safety. Practical part deals with measuring thermal conductivity at standard temperature and at high temperatures.
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Studying the behavior of concrete at high temperatures
Žák, Michal ; Sitek,, Libor (referee) ; Bodnárová, Lenka (advisor)
This bachelor's thesis is focused on behavior of concrete at high temperatures. The theoretical part describes processes, which take place in concrete at thermal loading and further there was described testing of concrete at high temperatures. Next there was described influence of high temperatures on each component of concrete and design of appropriate components for concrete exposed to high temperatures. In experimental part mixes was made with greywacke aggregate, amphibolite aggregate and with the addition of polypropylene fibers. In these mixes was determined the effect of high temperatures on the density of concrete, dynamic modulus of elasticity of concrete and compressive strength of concrete.
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Pile Foundations - Energy Piles
Hoza, Martin ; Leiter, Augustin (referee) ; Glisníková, Věra (advisor)
At a time when ecology and renewable energy sources come to the fore, the use of geothermal energy appears to be one of the suitable alternatives. The aim of this paper is to explain the function of ground source heat pumps, to mention factors affecting the efficiency of the system and discuss the technology of energy piles realization. This paper also focuses at risks associated with the soil temperature influencing and shows examples of realization.
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Properties of concrete with cement matrix at high temperatures
Fiala, Jiří ; Dvořák, Karel (referee) ; Bodnárová, Lenka (advisor)
This bachelor´s thesis deals with the behaviour of the cement concrete at high temperatures depending on the aggregate and cement type. The theoretical part describes the processes in the concrete structure at high temperatures affecting the individual concrete components. The design of concrete structure with basalt aggregate and four types of cement in the experimental part was carried out. The proof of physical-mechanical properties after thermal load was reviewed, particularly change of density, compressive strength and tensile strength in bending. The X-ray diffraction analysis was carried out with prepared test samples.
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