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Analysis of railway behavior on vehicles effects
Peňázová, Gabriela ; Kala, Jiří (referee) ; Salajka, Vlastislav (advisor)
The master’s thesis deals with the possibilities of railway track modeling. The computational models were created in ANSYS Classic. Simplified 2D model represents a longitudal half of classic single track construction, 3D models represent classic single track construction and RHEDA 2000 slab track. Static and dynamic response of 2D model was compared with analytical solutions by Timoshenko and Fryba. Static and dynamic responses of 3D models were analyzed and compared.
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Analysis of the steel structure of the bridge by FEM to the action of static load
Skorunka, Ondřej ; Hradil, Petr (referee) ; Salajka, Vlastislav (advisor)
The structures of bridges are one of the most demanding engineering structures. They fulfill an important social and economic role in the development of the given territory. From this perspective, it is necessary to pay close attention to the process of design, analysis, realization and service. This thesis deals with the static analysis of spatially curved and asymmetrical suspended foot bridge for pedestrians and cyclists. The first part is devoted to the analysis of structural deformation, while the second part is focused on the analysis of selected parts of the structure in terms of its stress.
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Dynamic analysis of a slender bridge construction with respect to wind actions
Prokop, Filip ; Kala,, Jiří (referee) ; Salajka, Vlastislav (advisor)
This work is focused on the dynamic effects with regard to impact of wind on a slender bridge structure, namely a variant of an overhead footbridge for pedestrians and cyclists, over a river. Attention is focused on finding the so-called default steady state, as well as modal analysis, where owen frequencies are calculated, which is the basis for further dynamic assessment. The main part is focused on modeling in a fluid field of ANSYS CFX, where the effects of wind on the structure are defined and calculated. The goal of the work is to make a dynamic response to vortex excitation and, on the basis of analysis, to assess the fatigue design.
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An assessment of a bridge construction on a dynamic load
Součková, Markéta ; Kala, Jiří (referee) ; Salajka, Vlastislav (advisor)
Diploma thesis deas with static and dynamic analysis of a steel arch footbridge. The footbridge structure 3D model was created in program ANSYS 12.1 and afterwards were made static and modal analysis on this computational model. Based on the results of~modal analysis was applied to design of dynamic wind loading on the model according to norms ČSN EN. The effects of this burden has been calculated steady response at resonance from harmonic analysis according to ČSN P EN 1991-2-4. To report according to ČSN EN 1991-1-4 was designed substitute quasistatic forces corresponding loads of wind on the construction and for evaluation was used static analysis.
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Interaction between Bridge Structure and Continuous Welded Rail
Vendel, Jiří ; Salajka, Vlastislav (referee) ; Ryjáček,, Pavel (referee) ; Plášek, Otto (advisor)
Understanding the interaction between a continuous welded rail and bridge structure is knowledge of all influences that participate in mutual coaction. Besides the material and cross-sectional characteristics of the bridge belonging to the scope of bridge design, there are several circumstances derived from external loads which have to be taken into account when designing new systems and assessing existing ones. From the physical point of view, each material has a natural tendency to change in length when the internal temperature changes. The continuous welded rail, concretely its central fixed zone, does not have this possibility due to its principle. However, if it is located on a bridge that freely expanse, the situation is significantly different. Due to the thermal expansion as well as the effects of railway transport, the bridge contributes significantly to the position and stress of the track. Usually, the most observed part of the continuous welded rail is the area above the sliding bearings of the bridge, where extremes of displacement and stress occur. Not only longitudinal expansion but also the rotation of the end of the supporting structure are the main sources of stresses at this point. This is because of the vertical load of the railway combined with the effects of traction and braking. If the exact degree of interaction between the bridge structure and the track (known as the longitudinal resistance of the track) were known, the design of a new or assessment of the existing system would have a better informative value, and we would not commit undesirable inaccuracies resulting from general normative provisions. It has been tested by many years of experience that from an operational and economic point of view, it is undoubtedly advantageous and desirable to establish a continuous welded rail wherever circumstances allow. So the goal of the research efforts is to approach more faithfully the real length limits of the bridge structure, in which
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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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Formulation the Methodology for Analysis the Seismic Response of the Piping Systems with Viscose Dampers
Chlud, Michal ; Salajka, Vlastislav (referee) ; Kanický, Viktor (referee) ; Malenovský, Eduard (advisor)
Viscous dampers are widely used to ensure seismic resistance of pipelines and equipment in nuclear power plants. Damping characteristics of these dampers are nonlinearly frequency dependent and thus causing complications in computational modelling of seismic response. Engineers commonly use two ways to deal with this nonlinearity: The first option is to consider damper by means of “snubber”. This is essentially linear spring element that is active for dynamic load and does not resist static loads. Snubber behaviour during seismic event is described by a equivalent stiffness (sometimes called pseudostiffness). The equivalent stiffness could be defined by the iterative calculations of piping natural frequencies and mode shapes taking into account seismic excitation. However, in complicated structures such as the main circulation loop of nuclear power plant the iterative calculation is difficult and could bring significant inaccuracies. On the other hand, the benefit of such modelling is a possibility to apply the commonly used linear response spectrum method for a solution. The second option is to describe damping characteristics using suitable rheological model. The seismic response is than determined by direct integration of the equations of motion. The behaviour of dampers is described exactly enough but the calculation and post-processing, especially nodal stresses time-histories, are time consuming. The goal of this work was to find a methodology for determining the seismic response of complex pipe systems with viscous dampers. Methodology allows a sufficiently accurate determination of the seismic response of piping systems and also allows obtaining of the results in effective time. The procedure is as follows. Firstly, specialized piping program (AutoPIPE) is used for the development of computational model. Next step is to determine a static response of structure and its verification with experimental measurements, if possible. Using script in Python language a computational model is converted from AutoPIPE into general finite element model in ANSYS system. Four-parameter Maxwell rheological model is used to describe behaviour of viscous dampers. Seismic load is represented by synthetic accelerograms. Newmark algorithm of direct integration of the equation of motion is used to obtain seismic response (only reactions and displacements in nodes of interest are necessary). Than is the equivalent stiffness is than gained from displacements and reactions as median value of their ratios. Received stiffness are subsequently transferred to AutoPIPE program where the seismic solution is performed using response spectra method. Finally, the dynamic response is combined with the static response and stress assessment according standards is done. The created methodology was applied in the seismic resistance calculation of the main circulation piping and piping of pressurizer in nuclear power plants type VVER 440 and type VVER 1000.
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The analysis of track response to railway vehicles
Kopeček, Josef ; Plášek, Otto (referee) ; Salajka, Vlastislav (advisor)
The diploma thesis deals with the assembly of numerical models of classical track using the finite element method in several variants. Models are compared with results obtained on analytical models. More complex models simulate the real behavior of a track running on a railway vehicle. The purpose is created methodology of modeling the railway track for use in static and dynamic analysis.
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Influence of technical and natural seismicity on building structures with focus on structures of masonry materials
Čada, Zdeněk ; Králik,, Juraj (referee) ; prof. Ing. Alois Materna, CSc., MBA (referee) ; Krejsa,, Martin (referee) ; Salajka, Vlastislav (advisor)
The dissertation deals with selected issues in the field of the calculation of the response of building structures which are excited with dynamic non-stationary displacement loading of its ground. Seismic load has been assumed. Procedures, how to work with seismic records with respect to the accuracy of dynamic calculations, how to modify the response spectrum to ensure the reliability, how to generate synthetic accelerogram requiring more accurate response, are recommended. Synthetic akcelerogram has been generated by own approaching, which has been used as the excitation function in the experimental seismic testing of autoclaved concrete brick building in model scale. Response values of motion in the measured points of the experiment were compared with the linear and nonlinear dynamic calculations by using the finite element method models. Different levels of detail of the numerical models have been used. The shear wall behaviour has been modelled by using constitutive models with brittle failure as well as using of non-linear interaction interface with possible delamination between the masonry bricks. The behaviour of the mathematical model of wall systems has been calibrated with respect to the measured data at shear wall experiments in real and model scale of walls.
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