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Vibration of slender bridge structure
Kika, Ondřej ; prof. Ing. Alois Materna, CSc., MBA (referee) ; Krejsa,, Martin (referee) ; Salajka, Vlastislav (advisor)
Doctoral thesis called Vibrations of slender bridge structures deals with comparison of constructions’ responses at different load model of pedestrians. Specifically, in practice commonly used model, where there are the effects of pedestrians replaced by forces acting in a certain place on the bridge and other model, which takes into account the load of pedestrians moving along the deck. Calculations of responses are performed by finite element method in program ANSYS. To obtain extreme values of responses It is used parametric calculation using the program OptiSlang. At first responses on the simplified constructions are evaluated for load of two pedestrians, as well as the responses on real bridges for load of two pedestrians and four pairs of pedestrians. Responses are also evaluated in terms of pedestrian’s comfort during use structures and analyzed for what groups of pedestrians are criteria still met and for which it is necessary to consider about use of devices to reduce vibration. Possible applications and design process of the vibration dampers are shown on different configurations on the bridges.
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Stochastic optimization of reinforced concrete structures
Venclovský, Jakub ; prof. Ing. Alois Materna, CSc., MBA (referee) ; Popela,, Pavel (referee) ; Štěpánek, Petr (advisor)
This Ph.D. thesis deals with creating an algorithm for stochastic optimization of the cross-sectional parameters of flat frames. After a brief introduction and outline of the thesis' goals is the summary of knowledge and results in the areas of deterministic and stochastic structural optimization. Further, the task of deterministic optimization is described, as it was solved in the previous thesis and papers which this thesis follows up on. Afterwards, the reformulation of the deterministic task to its stochastic form is described and the solution algorithm for such a task is introduced. The thesis ends with results of using the introduced algorithm on 6 examples.
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Strengthening of circular column subjected to lateral cyclic loading
Mansour, Mohamad ; prof. Ing. Alois Materna, CSc., MBA (referee) ; Fillo,, L´udovít (referee) ; Štěpánek, Petr (advisor)
Předložená disertační práce se zabývá zesílením kruhových železobetonových sloupů pomocí vlákny vyztužených polymerů (tzv. FRP – fibre reinforced polymer) namáhaných laterálním cyklickým zatížením. Tato výzkumná studie se zaměřuje na zkoumání využití FRP tkaniny pro dodatečné zesílení, zlepšení chování kruhových železobetonových sloupů a vytvoření návrhového algoritmu pro zesílení kruhového sloupu pomocí kompozitních FRP materiálů. Návrhový algoritmus byl odvozen na základě analytické studie, numerických simulací a výsledků experimentální činnosti. Na základě těchto výsledků byl navržen postup pro návrh zesílení sloupů ovinutím, který předpovídá chování železobetonových sloupů vystavených laterálním cyklickým zatížením. Při experimentální práci byly zkušební vzorky zatíženy současně axiální sílou a příčným cyklickým zatížením. Toto bylo provedeno dvěma různými způsoby. První způsob zatěžování byl proveden konstantní velikostí laterální síly po daný počet cyklů (1 milion) se sledováním změny deformace. A druhý způsob provedení spočíval v zatížení konstantní deformací se sledováním úbytku síly během zatěžovací zkoušky. Dizertační práce rovněž předkládá přehled současného stavu poznání zesílení železobetonových kruhových sloupů ovinutím FRP tkaninou vystavených působení seismického zatížení. Dále uvádí přehled návrhových metodik a normová ustanovení Eurokódu a ACI. Experimentální program byl proveden za účelem ověření chování ovinutých kruhových sloupů při působení laterálního cyklického zatížení. Závěr práce sumarizuje poznatky o chování sloupů zesílených ovinutím FRP tkaninou při působení laterálního cyklického zatížení a představuje empirický model pro návrh zesílení ovinutím při vysokém a nízkém cyklickém zatížení.
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Analysis of Thermoplastic Pipes in a Soil Environment
Ekr, Jan ; Kuklík,, Pavel (referee) ; prof. Ing. Alois Materna, CSc., MBA (referee) ; Gratza, Roman (advisor)
The doctoral thesis deals with an analysis of thermoplastics pipes in a soil environment, in particularly, pipes performed by using trenchless technologies. In the doctoral thesis, experiments of polyethylene pipes loaded by external hydrostatic pressure were performed. The aim of the experiments was to determine a behaviour and load-bearing capacity of the polyethylene pipes loaded by external hydrostatic pressure. For the experiments, a steel pressure chamber was designed and produced which allowed loading and observing a pipe during its loss of the stability. Mechanical properties of the pipe material were determined based on the tensile and bending tests. The series of detailed numerical analyses of the pipe experiments were performed. Various material models which take into account elastic, plastic and viscous behaviour of thermoplastic materials were used. In addition, series of standardized calculations of polyethylene pipes installed using trenchless technologies were performed. The aim was to create new design diagrams for practical assessment of these pipes placed in the partially deteriorated old pipes. In the case of the deteriorated old pipe, a numerical model for determination of design coefficients was created. These design coefficients were verified with standard values. Then, the results of the numerical model were compared with the results of the more complex numerical model which better take into account pipe-soil interaction of various soil types.
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Analysis of dynamical behaviour of slender structures and design of device to reduce vibration
Hanzlík, Tomáš ; Krejsa,, Martin (referee) ; prof. Ing. Alois Materna, CSc., MBA (referee) ; Salajka, Vlastislav (advisor)
Thesis deals with the modeling of pedestrian excitation of structures and obtaining the corresponding dynamic response of the structure. The trend of modern slender structures places more emphasis on the accuracy of modeling pedestrian dynamic excitation, which is difficult because of the intelligent behavior of pedestrians and the biological nature of the modeled pedestrian. First part of the thesis deals with traditional models of pedestrian excitation, based on application of pedestrian ground force to the model of construction. Models are explored on a model of slender footbridge for many different excitation variants in order to explore the specifics of the force excitation application and the structure response calculation. In second part of the thesis biomechanical pedestrian models are developed, including inertial forces, to calculate the pedestrian interaction with the structure. Parametric studies carried out on simplified structural models research the influence of design parameters of biomechanical models on dynamic response. The aim is to obtain a more accurate model of the pedestrian-construction system for refinement of the design of structures. The design of a tuned mass dampers for the reduction of pedestrian induced vibrations is also explored. Tuned mass dampers are devoted to parametric studies that deal with the influence of design parameters of the damper on the efficiency and design requirements of the device. The aim is to explore the design parameters and their influence on the efficient and economical design of the device. In the thesis were developed two biomechanical models, a simple biomechanical model with one vertical degree of freedom and a bipedal model of a human walking. Models have proven a certain degree of interaction when exciting light footbridges by one pedestrian. Bipedal model then also brought a partial insight into the mechanics of walking and the causes of pedestrian contact forces.
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Static Analysis of Parts of Thermoplastic Pipe Systems
Plášek, Jan ; Kuklík,, Pavel (referee) ; prof. Ing. Alois Materna, CSc., MBA (referee) ; Kytýr, Jiří (advisor)
Thermoplastic materials have significant nonlinear behaviour. The nonlinear behaviour is described by creep curves. The curves of creep modules are dependent on stress, temperature and time. The dissertation thesis deals with the approximation of the creep modules by Prony series. Subsequently three procedures are proposed to take account of creep modules. The proposed procedures are used in two applications. The first application deals with the ring stiffness value of a corrugated sewage pipe. The ring stiffness value is influenced by the creep modulus. The other one deals with a thermoplastic flange connection. The clamping force is dependent on the creep modulus of thermoplastics. The problems were solved by ANSYS program system.
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Strengthening reinforced concrete column confined by FRP fabric
Kostiha, Vojtěch ; prof. Ing. Alois Materna, CSc., MBA (referee) ; Bilčík,, Juraj (referee) ; Štěpánek, Petr (advisor)
The doctoral thesis deals with the strengthening of reinforced concrete columns by FRP fabric wrapping. Its aim is to describe the principles of confinement based on the analytical study, numerical simulations and the results of the experimental program. The description of the confinement philosophy is made with respect to the type of FRP material used. It was therefore possible to present a design process of confinement, which accurately predicts the behaviour of the confined columns. At the same time, some effects limiting the effect of confinement (e.g. the method of wrapping, the number of FRP fabric layers, the slenderness of the element, etc.) are included in the design. The dissertation also presents basic information about FRP material and its properties and gives an overview of design approaches of the FRP confined columns. The dissertation also pointing out the shortcomings of the design code ČSN EN 1992-1-1. The stated example highlights the significant variation in properties of confined concrete determined by selected approaches. This variation of properties complicates the design of this strengthening method. The experimental program was used to verify the basic principles of confinement and, through high columns, allowed a description of the behaviour in almost the whole range of interaction diagram. The conclusions of the work provide information on possible future research direction.
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DYNAMIC ANALYSIS OF THE SOIL-FOUNDATION INTERACTION
Martinásek, Josef ; prof. Ing. Alois Materna, CSc., MBA (referee) ; Kanický,, Viktor (referee) ; Salajka, Vlastislav (advisor)
Thesis deals with problems of the soil-structure interaction. In the theoretical part is described the approach to mathematical modeling of structure-foundation-soil interaction. The subsoil models are further described in detail, including the models with piles (both static and dynamics models). In the next chapter there is described the dynamics theory of the systems with single or more degrees of freedom. There is also an analysis of propagation, reflection and refraction of mechanical one-dimensional waves (P-wave, S-wave) and spatial waves (P- wave, SV-wave, SH-wave) and waves in homogeneous half-space (R-wave L-wave). The numerical analysis is logically sorted from hand calculation of the parameter change influence on the modal characteristics to complex computational FEM model of the machine with a foundation on piles placed in the spatial block of soil. Numerical studies aim to determine the influence of the subsoil model on the modal characteristics and thus confirm the absolute necessity of the subsoil model in tasks of dynamics. The next goal is to determine the appropriate key parameters of the computational model: the size of finite element, suitable shape of subsoil model, suitable inclination of boundary condition and suitable boundary conditions. For creating of set of computational models was used language APDL in conjunction with ANSYS software interface. All used input files are listed in the Annex.
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Shear bearing capacity of composite slabs
Holomek, Josef ; prof. Ing. Alois Materna, CSc., MBA (referee) ; Keršner, Zbyněk (referee) ; Bajer, Miroslav (advisor)
The subject of the submitted work is the experimental and theoretical investigation of composite slabs. The work also deals with creation of numerical models of composite slabs. The design of a new type of steel sheeting for composite slab according to nowadays standards requires full scale laboratory bending tests. An alternative to the bending tests are the small scale shear tests. The small scale shear tests as well as corresponding design methods have already been investigated by many researchers. Therefore several test arrangements and corresponding design methods can be found in literature but none of them is included in standards yet. The submitted thesis describes three of the alternative design methods: Slip- Block Test, Simplified Method and Built-up Bars. The test arrangement is proposed to be usable in all these methods. The small scale shear test have been performed in laboratory in several modifications. The results were used to calculate the bending resistance of the slab by the alternative design methods. The calculated bending resistances were mutually compared, compared with the performed bending tests resistances and the resistances by the methods described in Eurocode: m-k method and partial connection method. A sensitivity studies of the input parameters in alternative design methods are presented as well. The optimal design method for use in practice was searched and recommended based on the performed studies, accuracy and laboriousness of the methods. The shear tests were used also to measure longitudinal shear resistance of the additional shear anchors. The alternative design methods were used to predict bending resistance of the slab using these anchors and the results were compared. The numerical simulation of the composite action of the slab by the finite element methods is modelled in Atena software. The models serves to perform parametrical studies and to better understand of the behaviour of the slab in partial composite action.
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Vibration of slender bridge structure
Kika, Ondřej ; prof. Ing. Alois Materna, CSc., MBA (referee) ; Krejsa,, Martin (referee) ; Salajka, Vlastislav (advisor)
Doctoral thesis called Vibrations of slender bridge structures deals with comparison of constructions’ responses at different load model of pedestrians. Specifically, in practice commonly used model, where there are the effects of pedestrians replaced by forces acting in a certain place on the bridge and other model, which takes into account the load of pedestrians moving along the deck. Calculations of responses are performed by finite element method in program ANSYS. To obtain extreme values of responses It is used parametric calculation using the program OptiSlang. At first responses on the simplified constructions are evaluated for load of two pedestrians, as well as the responses on real bridges for load of two pedestrians and four pairs of pedestrians. Responses are also evaluated in terms of pedestrian’s comfort during use structures and analyzed for what groups of pedestrians are criteria still met and for which it is necessary to consider about use of devices to reduce vibration. Possible applications and design process of the vibration dampers are shown on different configurations on the bridges.
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