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Modelling of postcritical states of slender structures
Mašek, Jan ; Eliáš, Jan (referee) ; Frantík, Petr (advisor)
The aim of the presented thesis is to create a compact publication which deals with properties, solution and examination of behavior of dynamical systems as models of mechanical structures. The opening portion of the theoretical part leads the reader through the subject of description of dynamical systems, offers solution methods and investigates solution stability. As the introduction proceeds, possible forms of structure loading, damping and response are presented. Following chapters discuss extensively the possible approaches to system behavior observation and identification of nonlinear and chaotic phenomena. The attention is also paid to displaying methods and color spaces as these are essential for the examination of complex and sensitive systems. The theoretical part of the thesis ends with an introduction to fractal geometry. As the theoretical background is laid down, the thesis proceeds with an application of the knowledge and shows the approach to numerical simulation and study of models of real structures. First, the reader is introduced to the single pendulum model, as the simplest model to exhibit chaotic behavior. The following double pendulum model shows the obstacles of observing systems with more state variables. The models of free rod and cantilever serve as examples of real structure models with many degrees of freedom. These models show even more that a definite or at least sufficiently relevant monitoring of behavior of such deterministic systems is a challenging task which requires sophisticated approach.
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Discrete modelling of railway ballast
Dubina, Radek ; Petr,, Frantík (referee) ; Eliáš, Jan (advisor)
For modeling of particulate materials, discrete element method (DEM) is commonly used. It perceives every particle like a single body. A railway ballast loading by trains is a typical example of a particulate discrete material. By a passing train, static and dynamic forces act on a track bed. Cycling loading results in pernament changes in the railway ballast. Cavity creation, agglomeration and ballast cracking lead to damages in rail traffic. Usage of the discrete element method may reveal the real issues of the railway ballast and it may leads to a reduction of costs associated with a design and repairs. This thesis is focused on the ballast modeling and identification of the discrete model parameters. Obtained results are compared with real experiments from Nottingham University.
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Optimization of prestress tendon path
Středulová, Monika ; Lehký, David (referee) ; Eliáš, Jan (advisor)
The thesis explores possibilities of applying genetic algorithms on the problem of finding the optimal prestressed concrete tendon path. The objective of the thesis is to develop a genetic algorithm based on the Automatic Dynamic Penalization method and to test its robustness on selected analytical functions. Subsequently, the algorithm is connected to a Time Dependent Analysis module for the computation of prestressed concrete structure to solve selected examples of prestressed beams in the form of a constrained optimization problem. The algorithm is developed in the Python programming language with the help of the Distributed Evolutionary Algorithm library.
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Lagrange multipliers in linear elastostatics
Ondášová, Annamária ; Květoň, Josef (referee) ; Eliáš, Jan (advisor)
The thesis deals with the use of Lagrange multipliers, explaining the principle of their use and the calculating process. Lagrange multipliers are introduced into joints of a given truss structure. The calculation is conducted using minimalization of the potential energy and the principle of virtual work. Results are verified by direct elimination of the variables.
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Identification of changes in surface texture of the selected materials by the method of acoustic emission
Eliáš, Jan ; Bumbálek, Bohumil (referee) ; Mazal, Pavel (advisor)
This Bachelor thesis deals with monitoring changes in surface roughness of moving metal objects rubbing each other on selected parameters of acoustic emissions. Parameters of the AE signal during the movement of bronze and cast iron bodies on the surface of a fixed steel rod were measured, recorded and analyzed. These results can serve for further research on assessment possibilites of the degree of wear of a surface using the AE method. Measuring was performed using a measuring product intended for AE and the Dakel sensors and measuring software.
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Simulation of concrete fracture using nonlocal model
Květoň, Josef ; Vořechovský, Miroslav (referee) ; Eliáš, Jan (advisor)
The thesis deals with nonlocal model simulations of the three-point-bening test series. The model is applied to set of beams of variable size and notch depth. The intention is to identify such parameters that would provide the response of the nonlocal model similar to experimental data from the comprehensive fracture tests performed at the Northwestern University. Size and shape of the process zone are estimated from the discrete model results and according to that the parameters of weight function and material for the nonlocal model are identified. Results obtained with the model are compared to the experimental data.
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Optimalization of Financing of the Selected Company - Cost Management
Eliáš, Jan ; Duranti, David (referee) ; Ptáček, Roman (advisor)
The subject of this bachelor thesis is analysis of the cost management of a particular enterprise. The thesis is divided into two parts, theoretical and practical. The purpose of the theoretical part is describing the subject matter and familiarizing with key terms and with the methodology of analysis of the cost management. The practical part is then focused on analysis of the current state of cost management in the enterprise ALDO Metal s.r.o which is a manufacturing company focused on custom manufacture of metal parts and units. In conclusion the overall results of the analysis are evaluated and the author outlines improvement proposals and recommendations to improve the cost management in this enterprise.
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Micropolar continuum and its applications in structural mechanics
Fleischerová, Beáta ; Vořechovský, Miroslav (referee) ; Eliáš, Jan (advisor)
Práca sa zaoberá mechanikou kontinua. Konkrétne je zameraná na lineárnu elasticitu homogénnych izotropných pevných telies. Pre dve rôzne kontinuá – klasické kontinuum a mikropolárne je odvodená silná aj slabá formulácia. Cosseratovo (mikropolárne) kontinuum predstavuje rozšírenie ku klasickému, kde je uvažovaný ďalší stupeň voľnosti - nezávislá rotácia. Mikropolárne kontinuum definuje ďalšie dve materiálové konštanty, ktoré súvisia s rotáciou. V súčasnosti je metóda konečných prvkov veľmi populárny spôsob približného riešenia rovníc lineárnej elasticity. Pre účely diplomovej práce bol vyvinutý program pre MKP riešenie 2D rovinných úloh. Pre lepšiu predstavu o vplyvu rôznych parametrov na správanie sa oboch kontinuí analyzujeme jednoduchý príklad konzolového nosníka. Riešenia analyzujeme s využitím 4-uzlového štvorhranného elementu, ktorý je jedným z najpoužívanejších pre MKP. V Cosseratovom kontinue by mali byť rotácie previazené skrz parameter vnútornej dĺžky, čo by sa malo odzrkadliť zvýšenou tuhosťou telesa. Úlohou práce je porovnať výsledky z oboch kontinuí a potvrdiť tento predpoklad.
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Modeling of fracture process in quasi-brittle materials
Klon, Jiří ; Eliáš, Jan (referee) ; Veselý, Václav (advisor)
This work is focused on the evaluation of the selected fracture parameters of quasi-brittle material, especially concrete, and an assessment of their dependence on the size and shape of the fracture process zone developing at the tip of the macroscopic crack during fracture. For this purpose, experimentally obtained loading diagrams published in the scientific literature have been utilized. These diagrams have been processed into a form enabling creation and calibration of numerical models of these tests in the ATENA FEM program. The results obtained from simulations of the three-point bending tests on beams of four sizes, with three notches lengths, using the created numerical models were used for determination of fracture parameters of concrete. Results of the work consist of the determined values of the specific energy dissipated for creation of new surfaces of the effective crack and an estimation of the specific energy dissipated in the volume of the fracture process zone, which exhibits specific parameters for each beam size and notch length.
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Nonlinear analysis of reinforced concrete foot failure
Dubina, Radek ; Václav,, Veselý (referee) ; Eliáš, Jan (advisor)
Reinforced concrete monolithic feet are one kind of shallow foundation used mainly under column systems. These systems transfer the load from upper floors through columns to the feet and through them to the foundation soil. Interaction between the foot and the foundation soil plays an important role due to the system sensitivity to the uneven settlement. Feet has to resist shear induced by vertical force and bending moment caused by stress in footing bottom. The work is devoted to design of the foot according to European standard Eurocode 2. It is then focused on numerical simulation of foot failure and calculation of the corresponding maximal vertical force in the column using a 3D model with nonlinear material models of subsoil, reinforcement and concrete. The calculations are done in software ATENA 3D for different variants of subsoil, reinforcement and foot shape. Results according to European standard and nonlinear analysis are compared.
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