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Development of methods for analysys road safety barriers in terms of dynamic effects
Koudelka, Ivan ; Krejsa,, Martin (referee) ; prof. Ing. Alois Materna, CSc., MBA (referee) ; Salajka, Vlastislav (advisor)
The presented work analyses the methodology and approach of the legislation. It presents in the press presented results of numerical modelling of the impact of vehicles crashed into barriers that are being solved in the Czech Republic and worldwide. It presents a recommendation of a methodology for assessing crash barriers. The methodology follows the basic principles used in the TP 101 and EN 1991-1-1. The kinetic energy of the vehicle at the moment of impact is replaced with substitute static force, whose effects are comparable with those of a vehicle collision. The supporting structure of crash barriers is implemented in compliance with means of statics. The calculation includes the vehicle deformation, which represents the real distribution of the energy absorbed by the deformation of the vehicle and the energy that crash barriers need to absorb. The proposed methods allow to take into account non-linear behaviour of the structure both in terms of geometry and in terms of material nonlinearity. The work also deals with the interpretation of various types of support structures in the computational model. A specific case is used for a demonstration of a way of modelling the elastic supporting column of crash barriers in the soil, or modelling the friction of a loose concrete block over the surface. To ensure the proper position of interconnected loose blocks corresponding to the reality, a method of modelling the place of a possible contact of the breakthrough is drafted. A significant contribution to the more accurate calculation is achieved by sequential increase of the load on the construction by using load increment and measurement of energy increases absorbed by the deformation in each step. The presented methodology is an effective tool to assess crash barriers. For the application of this tool, using common resources and facilities available to almost every designer dealing with statics of structures is sufficient. In conclusion, the knowledge obtained fr
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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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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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Study of impact of a transport vehicle into a structure.
Sychrová, Šárka ; Salajka, Vlastislav (referee) ; Němec, Ivan (advisor)
Master's thesis deals with the analysis of the impact of transport vehicle on a building structure. Transport vehicle is represented by an airliner and building structure is represented by a containment of a nuclear power plant. The aim of thesis was to explore the possibility of numerical simulation of an impact of transport vehicle on a building structure utilizing the RFEM program and evaluation of the damage extent.
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Static and dynamic assessment of an outlook tower construction
Valíček, Jan ; Kala, Jiří (referee) ; Salajka, Vlastislav (advisor)
This thesis deals with static and dynamic analysis of an lookout tower construction. For dynamic analysis a computational model in ANSYS software is created. Static analysis is performed by Scia Engineer software. Both of this software use finite element method. It is also focused on wind load determination by Eurocode 1, structural factor calculation, modal analysis and vortex shedding. Verification of selected parts according to Eurocodes is included.
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Dynamic analysis of an in-line arranged cylindrical chimney
Harazim, Petr ; Kanický, Viktor (referee) ; Salajka, Vlastislav (advisor)
The diploma thesis deals with the response of a steel smokestack structure to wind loads. A detailed computational model implementing the finite element method was created in accordance with the available drawing documentation. The new smokestack was placed next to an existing one, thus it can be assumed that these two structures will affect each other. The thesis also elaborates on the problems of aerodynamic and aeroelastic stability of the earlier smokestack; in particular, the occurrence of vortex shedding in resonance with eigenfrequency of the structure, with the use of the program ANSYS CFX. The evaluation of the structure includes survey of the strength and deflections of the structure. The calculations are in accordance with valid ČSN EN norms.
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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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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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Nonlinear analysis of reinforced concrete structures
Král, Petr ; Salajka, Vlastislav (referee) ; Hradil, Petr (advisor)
The aim is to design and evaluate nonlinear beams analysis, which will be subjected by four – point bending. Nonlinear analysis will be performed and evaluated on three beam models, the first of which will be made from plain concrete, the second of which will be made from reinforced concrete with reinforcement bars in the domain of tensile stress and the third of which will be made from reinforced concrete with reinforcement bars in domains of tensile and compressive stress. The thesis will be included formation of appropriate FE models, performance of nonlinear calculations with using nonlinear material model from a library of nonlinear material models multiPlas in the programming environment of software ANSYS and subsequent evaluation of results. Evaluation of results will consist from evaluation of nonlinear beams analysis and from evaluation of beams analysis according to ČSN EN 1992 – 1 – 1 without reinforcement bars and with reinforcement bars in these variants, next from comparison of nonlinear beams analysis with a beams analysis according to ČSN EN 1992 – 1 – 1 and finally from evaluation of the yield condition, which will be applied to the beams.
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