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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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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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