2025-06-24
13:59 |
Úplný záznam
|
2025-06-24
13:59 |
Úplný záznam
|
2025-06-24
13:59 |
Virtuální procházky historickými krovy: Nové nástroje pro zpřístupnění skrytých součástí kulturního dědictví
Bláha, Jiří ; Buzek, Jaroslav ; Novotný, Jakub
Historické krovy z důvodu své konstrukční podstaty a umístění představují pro běžného návštěvníka často obtížně nebo zcela nepřístupnou část stavby. Cílem příspěvku je zhodnotit potenciál informačních a komunikačních technologií (ICT) pro zpřístupňování a popularizaci této významné vrstvy hmotného architektonického dědictví. Nejprve je podán přehled\ntradičních metod dokumentace a zobrazování krovových konstrukcí a uvedeny jejich výhody a omezení. Následně jsou představeny moderní ICT nástroje (LiDAR, fotogrammetrie, 3D skenování a modelování, digitální mapy, rozšířená realita) a jejich aplikace na případových studiích konkrétních historických krovů (Cheb a Jihlava). Práce využívá metodiku případových studií. Díky stále dokonalejším a dostupnějším nástrojům pro převedení fyzicky dochovaných konstrukcí do virtuálního prostředí mohou odborníci efektivněji třídit získaná terénní data a specifikovat užitnou, historickou či památkovou hodnotu příslušného krovu. Virtuální prohlídky a interaktivní modely využívající ICT zpřístupňují tyto památky všem zájemcům, a to bez ohledu na jejich fyzické možnosti či omezení. Zároveň přispívají k rozšíření turistické\nnabídky a posilují povědomí o hodnotách hmotného i nehmotného (dobové řemeslně-technologické postupy) kulturního dědictví.
Úplný záznam
|
2025-05-24
00:00 |
Galerkin-type solution of non-stationary aeroelastic stochastic problems
Fischer, Cyril ; Náprstek, Jiří
The assessment of vibration characteristics in slender engineering structures, influenced by both deterministic harmonic and stochastic excitation, poses a challenging problem. Due to its complexity, transverse vibration of the structure (relative to the wind direction) is typically modelled using the single-degree-of-freedom van der Pol-type equation. Determining the response probability density function comprises solving the Fokker-Planck equation, a task that generally necessitates the use of approximate numerical methods. Some of these methods rely on Galerkin-type approximation employing orthogonal polynomial or exponential-polynomial basis functions. This contribution reviews available techniques for stationary and non-stationary cases and proposes some modifications while highlighting unresolved questions in the field.
Úplný záznam
|
2025-05-24
00:00 |
Application of blockage corrections to U-beams with porous railings
Michálek, Petr ; Hračov, Stanislav ; Macháček, Michael
Different models of u-beams with porous flanges were tested in wind tunnel with the use of force and moment measurements. Due to high wind tunnel blockage ratio, the wind tunnel blockage corrections were applied to the measured forces and moments. The tested model beams were manufactured in two scales, i. e. large model and small model with half dimensions of the large model in order to test Reynolds number independence. Different blockage ratio calculation methods were used on the large and small U-beam model across various wind attack angles. The Maskell blockage correction method was applied to the experimental drag coefficient data.
Úplný záznam
|
2025-05-24
00:00 |
Aerodynamic coefficients and pressure distribution on U-beams with porous flanges
Macháček, Michael ; Hračov, Stanislav ; Dejmal, Karel
This study presents the results of wind tunnel experiments on U-shaped beams with either solid flanges or flanges with 50% porosity. Aerodynamic drag and lift coefficients, along with pressure coefficient distributions on the beam surfaces, were evaluated and compared for both configurations. The findings demonstrate that flange porosity significantly affects the aerodynamic forces and flow around the U-beam. Across most angles of attack, the solid-flange beam exhibited higher drag than the porous-flange beam. However, within the range of approximately −11.5° to −5.5°, the porous configuration showed higher drag. Furthermore, at negative angles of attack, the lift force on the porous-flanged beam acted in the opposite direction to that on the solid-flanged beam. Finally, incorporating flange porosity reduced the magnitude of suction pressures on both the top and bottom surfaces of the U-beam.
Úplný záznam
|
2025-05-24
00:00 |
Influence of blockage effect and of turbulence intensity on the flow around U-profile
Ledvinková, Blanka ; Hračov, Stanislav ; Macháček, Michael
The significant distortion of wind tunnel data may occur, when the boundary layer of the tunnel wall interacts and modifies the flow around the tested object. To numerically evaluate the influence of this blockage effect on aerodynamic coefficients, 2D RANS simulations of airflow around porous and non-porous U-profiles in two computational domains with varying distances between the top and bottom walls were carried out. Another factor investigated in relation to aerodynamic characteristics was the turbulence intensity of the inlet stream. Simulations of the U-profile at various impact angles, using two differently sized computational domains and two levels of turbulent intensity, were performed. The mean drag and lift coefficients, fluctuating lift coefficient, and Strouhal number were evaluated.
Úplný záznam
|
2025-05-24
00:00 |
Numerical simulation of transient aeroelastic phenomena influenced by stochastic resonance in cross flow conditions
Náprstek, Jiří ; Fischer, Cyril
Stochastic resonance is a phenomenon observed in nonlinear dynamical systems with bistable behavior under combined deterministic and stochastic excitation. In its classical form, it is modeled using a Duffing-type oscillator subjected to harmonic forcing and additive white noise, resulting in noise-assisted transitions between stable states. This study investigates numerical methods for capturing transient effects related to stochastic resonance in the context of aeroelastic post-critical behavior, with a focus on a prismatic beam exposed to cross air flow. Motivated by wind tunnel observations, stochastic resonance is explored as a theoretical framework for modeling complex aeroelastic responses in bridge decks. Two computational approaches are employed: direct stochastic simulation using Monte Carlo methods, and numerical solution of the associated Fokker–Planck equation using the method of lines. The results highlight the capability of these methods to reproduce resonance-driven switching and demonstrate their potential for predicting transient aeroelastic responses relevant to the stability of slender structures under aerodynamic loading.\n
Úplný záznam
|
2025-05-24
00:00 |
FEM-based modeling of generalized amplitudes in stochastic van der Pol systems
Fischer, Cyril ; Náprstek, Jiří
This paper investigates various approaches for approximating the stationary aeroelastic response characteristics under near-resonance conditions, with a focus on the lock-in regime. A reduced form of the Fokker–Planck equation—derived via stochastic averaging—is used to represent the long-term behavior. Comparative analysis is performed between traditional finite element solutions and refined semi-analytical techniques based on a Galerkin-type expansion of an analytical solution available for exact resonance conditions. Although full verification via Monte Carlo simulations is constrained due to the elusive nature of the generalized partial amplitudes inherent in the reduced FPE framework, indicative comparisons reveal an unexpectedly analogy across methods. These results highlight both the practical value and the limitations of different modeling strategies in the probabilistic assessment of nonlinear systems.\n
Úplný záznam
|
2025-05-24
00:00 |
Results of comparative damage detection case study
Bayer, Jan ; Urushadze, Shota
A significant amount of attention has been devoted to rapid bridge testing in recent years at the Institute of Theoretical and Applied Mechanics. New methods, such as the Vehicle Scanning Method and Moving Impulse Load Testing, have been developed and/or tested on a scaled laboratory bridge model. This article summarizes all conducted tests, discusses the evaluation methods used, presents the results obtained, and explores possibilities for their improvement. Among the tested methods, the application of Moving Impulse Load (MIL) moving at slow speed, with an excitation frequency around the first natural frequency of the tested bridge, appears to be the most promising. Two passages of the MIL allow for an approximate estimation of the dominant natural frequencies, while repeated passages at small velocity increments provide an excellent means of detecting changes in structural stiffness.
Úplný záznam
|
|
|
|
host ::
