Shock waves generated by corona-like discharges in water
Hoffer, Petr
2014 - English Available at various departments of the ČVUT. Shock waves generated by corona-like discharges in water

Hoffer, Petr
České vysoké učení technické v Praze, 2014

Nestandardní reprezentace čísel
Masáková Zuzana; Dombek Daniel; Frougny Christiane
2014 - English Available at various departments of the ČVUT. Nestandardní reprezentace čísel

Masáková Zuzana; Dombek Daniel; Frougny Christiane
České vysoké učení technické v Praze, 2014

High performance silicate composites in environmentally optimized floor structures
Hájek Petr; Novotná Magdaléna; Kolísko Jiří
2014 - English Stavební průmysl má významný dopad na životní prostředí. Spotřebovává nejvíce primárních surovin a energetických zdrojů. Současně produkuje značné množství škodlivých emisí. K dosažení udržitelného rozvoje je proto nezbytné přistoupit k různým ekologickým opatřením.Building sector has significant impact on the global environment. It is the biggest consumer of the primary materials and energetic sources, and at the same time it is the producer of the harmful emissions. Implementation of the environmental measures in building structures is inevitable in order to reach the sustainable development. Keywords: Vysokohodnotné silikátové kompozity; stropní konstrukce; environmentální optimalizace; LCA; alkalicky aktivovaný beton; kazetové stropní konstrukce; dřevo-betonové stropní konstrukce; vylehčující vložky. Available at various departments of the ČVUT. High performance silicate composites in environmentally optimized floor structures

Stavební průmysl má významný dopad na životní prostředí. Spotřebovává nejvíce primárních surovin a energetických zdrojů. Současně produkuje značné množství škodlivých emisí. K dosažení udržitelného ...

Hájek Petr; Novotná Magdaléna; Kolísko Jiří
České vysoké učení technické v Praze, 2014

Numerická charakteristika vlastností asfaltových směsí
Luxemburk František; Žák Josef; Novotný Bohuslav
2014 - English Principy lineární viskoelasticity a vybrané reologické modely, běžně používané v oboru asfaltových směsí, jsou shrnuty v úvodu disertační práce. Teorie lineární viskoelasticity je dále použita k analýze materiálových vlastností asfaltových směsí. Dále je prezentován postup spojení komplexní křivky z dynamických oscilačních měření k akumulované funkci poddajnosti získané ze Zkoušky pojíždění kolem. V disertační práci je diskutována využitelnost tohoto parametru s ohledem na chování asfaltové hutněné směsi in situ. Poissonovo číslo asfaltových směsí je prezentováno jako funkce času na základě relaxačních a dynamických oscilačních měření na válcových tělesech. Část disertační práce je zaměřena na popis návrhu konstrukce vozovky a uvádí postu pro možné zohlednění opakovatelnosti a reprodukovatelnosti zkoušky odolnosti proti únavě. V disertační práci je dále prezentován koncept vyvinutého zařízení s názvem Jednoosý smykový přístroj (UST). Použitelnost zařízení UST je posuzována na základě korelace se zařízením Superpave Shear Tester, zařízení určené pro návrh asfaltových hutněných směsí a hodnocení odolnosti asfaltových směsí proti vzniku trvalých deformací. Predikce hloubky koleje, vypočtené inkrementální simulací, a výsledky z Welchova modifikovaného t-testu jsou diskutovány. V disertační práci je uveden způsob výpočtu akumulované ustálené funkce poddajnosti z opakovaných smykových testů. Tento nekonvenční parametr je použitelný jako kritérium pro stanovení odolnosti materiálu proti trvalým deformacím.The linear viscoelastic principles and selected rheological models commonly used in asphalt mixtures are summarized in the introduction. The principles of linear viscoelastic theory are further applied on the material properties evaluation. The appended master curves of dynamic material functions to accumulated compliance derived from Hamburg-Wheel Tracking Test are presented and their usability in sense of Hot Mix Asphalt (HMA) performance is discussed. HMA Poisson?s ratio is reported as a function of time determined based on relaxation and small amplitude oscillation tests on cylindrical specimens. Part of the dissertation is focused on the description of a road pavement design procedure and introduces a specific method of considering the repeatability and reproducibility of the fatigue resistance test. Dissertation presents concept of a newly developed Uniaxial Shear Tester (UST). The UST applicability is assessed on the basis of correlation with Superpave Shear Tester, a tool broadly recognized for asphalt mix design and rutting susceptibility evaluation. The incremental recursive rut depth predictions are calculated and the Welch-modified t-test results are discussed. The principles of accumulated equilibrium compliance derivation from repeated shear test are presented as offbeat criterion for pavement susceptibility to permanent deformation. Keywords: asfaltové hutněné směsi; lineární viskoelasticita; smykové vlastnosti; jednoosý smykový přístroj; hloubka kolejí; akumulovaná ustálená funkce poddajnosti Available at various departments of the ČVUT. Numerická charakteristika vlastností asfaltových směsí

Principy lineární viskoelasticity a vybrané reologické modely, běžně používané v oboru asfaltových směsí, jsou shrnuty v úvodu disertační práce. Teorie lineární viskoelasticity je dále použita k ...

Luxemburk František; Žák Josef; Novotný Bohuslav
České vysoké učení technické v Praze, 2014

Flexibilní bydlení - universální prostor v bytě.
Kohout Michal; Yunitsyna Anna; Tichý David
2014 - English Available at various departments of the ČVUT. Flexibilní bydlení - universální prostor v bytě.

Kohout Michal; Yunitsyna Anna; Tichý David
České vysoké učení technické v Praze, 2014

Pulsed plasma soft X-ray source in biomedical research
Fidler Vlastimil; Brůža Petr
2014 - English Available at various departments of the ČVUT. Pulsed plasma soft X-ray source in biomedical research

Fidler Vlastimil; Brůža Petr
České vysoké učení technické v Praze, 2014

X-ray phase contrast imaging with hybrid semiconductor pixel detectors
Pospíšil Stanislav; Krejčí František
2014 - English Available at various departments of the ČVUT. X-ray phase contrast imaging with hybrid semiconductor pixel detectors

Pospíšil Stanislav; Krejčí František
České vysoké učení technické v Praze, 2014

Numerical modeling of fluid-structure interaction
Patzák Bořek; Krybus David; Kabele Petr
2014 - English A coupled fluid-structure interaction (FSI) analysis represents a challenging task from engineering point of view. Except a few special FSI problems, the only way to perform interaction analysis is the use of experimental or numerical methods. This thesis deals with the numerical modeling of fluid-structure interaction adopting so-called staggered approach, which solves both phases separately and employs information exchange on the interface to enforce compatibility. The main objectives of this work are the formulation and development of a numerical model for the analysis of FSI problems, its implementation and validation on benchmark examples. The fluid flow is modeled by the finite element method using Lagrangian formulation of governing equations. This approach is based on the particle finite element method. The computational domain is discretized by abstract particles, for which the incompressible Navier-Stokes equations are solved in each time step, resulting in velocities and pressure values. Lagrangian approach requires frequent remeshing to avoid distortion of background elements defined by topology of particles. For these purposes, a mesh generator based on the Delaunay triangulation is implemented. The boundary of the domain is recovered by the Alpha Shape concept. The developed model of fluid flow is validated on the examples of the water column collapse and free oscillation of a liquid in a container. The coupling of the fluid and structural problems is enabled by the implementation of iterative solver using the Dirichlet-Neumann approach based on the exchange of velocity and pressure values on the interface. Capabilities of the pilot implementation are illustrated on an example of clamped elastic gate of a fluid container.A coupled fluid-structure interaction (FSI) analysis represents a challenging task from engineering point of view. Except a few special FSI problems, the only way to perform interaction analysis is the use of experimental or numerical methods. This thesis deals with the numerical modeling of fluid-structure interaction adopting so-called staggered approach, which solves both phases separately and employs information exchange on the interface to enforce compatibility. The main objectives of this work are the formulation and development of a numerical model for the analysis of FSI problems, its implementation and validation on benchmark examples. The fluid flow is modeled by the finite element method using Lagrangian formulation of governing equations. This approach is based on the particle finite element method. The computational domain is discretized by abstract particles, for which the incompressible Navier-Stokes equations are solved in each time step, resulting in velocities and pressure values. Lagrangian approach requires frequent remeshing to avoid distortion of background elements defined by topology of particles. For these purposes, a mesh generator based on the Delaunay triangulation is implemented. The boundary of the domain is recovered by the Alpha Shape concept. The developed model of fluid flow is validated on the examples of the water column collapse and free oscillation of a liquid in a container. The coupling of the fluid and structural problems is enabled by the implementation of iterative solver using the Dirichlet-Neumann approach based on the exchange of velocity and pressure values on the interface. Capabilities of the pilot implementation are illustrated on an example of clamped elastic gate of a fluid container. Keywords: Particle finite element method; Fluid-structure interaction; Numerical methods Available at various departments of the ČVUT. Numerical modeling of fluid-structure interaction

A coupled fluid-structure interaction (FSI) analysis represents a challenging task from engineering point of view. Except a few special FSI problems, the only way to perform interaction analysis is ...

Patzák Bořek; Krybus David; Kabele Petr
České vysoké učení technické v Praze, 2014

Creep and shrinkage of concrete subjected to variable environmental conditions
Jirásek Milan; Havlásek Petr; Vítek Jan
2014 - English This thesis deals with the numerical modeling of concrete creep and shrinkage at variable environmental conditions. At lower relative humidity concrete creeps more slowly than at full saturation but during drying it creeps faster. Creep is also accelerated at elevated temperature or by temperature variations.One of the physically based models for concrete creep and shrinkage that takes into account variable temperature and humidity is based on the theory of microprestress and solidification (MPS). Unlike the MPS model to the models from the design codes which use the average cross-sectional approach, the MPS model operates at the material point level, which makes it possible to capture the stress distribution more realistically. Assessment of the MPS model is the main topic of this work. Several severe deficiencies of this model have been identified and appropriate remedies have been proposed. Comparing to the experiments, the original formulation of the MSP model exhibited the opposite size-effect on drying creep, spurious sensitivity to the particular choice of relative humidity and excessive compliance during the repeated cycles of temperature and relative humidity. First, the model was reformulated, making the governing equations simpler yet equivalent. Afterwards, the model was improved and validated on typical examples from the literature.The MPS model was implemented into the open-source finite element package OOFEM developed mainly at the Department of Mechanics, Faculty of Civil Engineering, CTU in Prague.The model was calibrated on the experimental specimens, and afterwards applied in the analysis of a real-world structure - a concrete floor subjected to drying. The results indicate that even the improved model needs further improvements regarding the relationship between shrinkage and relative humidity; however, this relationship cannot be uniquely identified from the currently available experimental data. The engineering approach of shrinkage updating based on short-time measurements has also been questioned.This thesis deals with the numerical modeling of concrete creep and shrinkage at variable environmental conditions. At lower relative humidity concrete creeps more slowly than at full saturation but during drying it creeps faster. Creep is also accelerated at elevated temperature or by temperature variations.One of the physically based models for concrete creep and shrinkage that takes into account variable temperature and humidity is based on the theory of microprestress and solidification (MPS). Unlike the MPS model to the models from the design codes which use the average cross-sectional approach, the MPS model operates at the material point level, which makes it possible to capture the stress distribution more realistically. Assessment of the MPS model is the main topic of this work. Several severe deficiencies of this model have been identified and appropriate remedies have been proposed. Comparing to the experiments, the original formulation of the MSP model exhibited the opposite size-effect on drying creep, spurious sensitivity to the particular choice of relative humidity and excessive compliance during the repeated cycles of temperature and relative humidity. First, the model was reformulated, making the governing equations simpler yet equivalent. Afterwards, the model was improved and validated on typical examples from the literature.The MPS model was implemented into the open-source finite element package OOFEM developed mainly at the Department of Mechanics, Faculty of Civil Engineering, CTU in Prague.The model was calibrated on the experimental specimens, and afterwards applied in the analysis of a real-world structure - a concrete floor subjected to drying. The results indicate that even the improved model needs further improvements regarding the relationship between shrinkage and relative humidity; however, this relationship cannot be uniquely identified from the currently available experimental data. The engineering approach of shrinkage updating based on short-time measurements has also been questioned. Keywords: concrete; creep; shrinkage; drying; microprestress; finite elements; numerical modeling Available at various departments of the ČVUT. Creep and shrinkage of concrete subjected to variable environmental conditions

This thesis deals with the numerical modeling of concrete creep and shrinkage at variable environmental conditions. At lower relative humidity concrete creeps more slowly than at full saturation but ...

Jirásek Milan; Havlásek Petr; Vítek Jan
České vysoké učení technické v Praze, 2014

Mathematical and physical modelling of pipe flow of settling slurries
Matoušek Václav; Krupička Jan
2014 - English Presented study deals with investigation of two phase flow composed of water and settling solid particles. The main contribution is a set of results of experiments, carried out in pipe loops at the Institute of Hydrodynamics of the Academy of Sciences of the Czech Republic, and at the Faculty of Civil Engineering of Czech Technical University in Prague. The experiments were focussed to ability of flow to convey solid fraction and on effect of solid fraction on flow friction, particularly in the case of flow above eroded surface of stationary deposit formed at the pipe bottom. Experimental methodology and results are reported. Special attention is paid to evaluation of concentration profiles by means of radiometric density meter which was employed to extend available database on inner structure of settling slurry flows in pipes. Obtained findings on specific flow aspects are implemented in a predictive model for stratified flow in pipes. The model performance is discussed on the base of comparison of model predictions with measured data. Results on friction at strongly eroded surface of granular bed would be applicable not only in pipes with deposit but also in the field of river hydraulics.Presented study deals with investigation of two phase flow composed of water and settling solid particles. The main contribution is a set of results of experiments, carried out in pipe loops at the Institute of Hydrodynamics of the Academy of Sciences of the Czech Republic, and at the Faculty of Civil Engineering of Czech Technical University in Prague. The experiments were focussed to ability of flow to convey solid fraction and on effect of solid fraction on flow friction, particularly in the case of flow above eroded surface of stationary deposit formed at the pipe bottom. Experimental methodology and results are reported. Special attention is paid to evaluation of concentration profiles by means of radiometric density meter which was employed to extend available database on inner structure of settling slurry flows in pipes. Obtained findings on specific flow aspects are implemented in a predictive model for stratified flow in pipes. The model performance is discussed on the base of comparison of model predictions with measured data. Results on friction at strongly eroded surface of granular bed would be applicable not only in pipes with deposit but also in the field of river hydraulics. Keywords: Slurry Pipe; Sediment Transport; Experiment; Bed Shear; Concentration Profiles. Available at various departments of the ČVUT. Mathematical and physical modelling of pipe flow of settling slurries

Presented study deals with investigation of two phase flow composed of water and settling solid particles. The main contribution is a set of results of experiments, carried out in pipe loops at the ...

Matoušek Václav; Krupička Jan
České vysoké učení technické v Praze, 2014