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Theoretical analysis of selected trajectories inscribed by a ball freely rolling in a spherical cavity
Náprstek, Jiří; Fischer, Cyril
2022 - English
Indirect monitoring of structures is significantly complicated when an artificial vibration absorber has to be taken into account. Knowledge of the absorber’s behaviour is necessary in order to correctly distinguish the response types obtained during an drive-by measurement. In this work, the mathematical model of the ball-type vibration absorber is used, which is based on the Lagrangian formalism. Three first integrals are identified when no external excitation nor damping is assumed. The paper illustrates the power of this approach, which enables a detailed analysis of free movement of the ball in the spherical cavity. Properties of several particular trajectories depending on initial conditions are presented.
Keywords:
slender structure; vibration absorber; first integral; rolling sphere; structural health monitoring
Available in digital repository of the ASCR
Theoretical analysis of selected trajectories inscribed by a ball freely rolling in a spherical cavity
Indirect monitoring of structures is significantly complicated when an artificial vibration absorber has to be taken into account. Knowledge of the absorber’s behaviour is necessary in order to ...
Ochrana památkových objektů proti vibracím
Urushadze, Shota; Pirner, Miroš; Bayer, Jan
2022 - Czech
Předkládaný památkový postup byl vytvořen v letech 2018–2021 při řešení úkolu NAKI č. DG18P02OVV040, nazvaného 'Památky v pohybu', financovaného MK ČR. Podkladem pro vypracování tohoto památkového postupu byla 30‐letá činnost Prof. Pirnera, Ing. Urushadzeho a Ing. Bayera v oblasti technické seizmicity a stavební dynamiky obecně. Navržený památkový postup je vlastně metodickým návodem, jak postupovat, pokud se objeví u památek nějaké poruchy nebo negativní projevy, které by mohly souviset s vibracemi, včetně způsobů jejich řešení. K jednotlivým bodům postupu jsou uváděny příklady z dlouholeté praxe. Obecně tato vyšetřování zahrnují teoretickou a experimentální analýzu včetně terénního průzkumu, nedestruktivní a laboratorní testy na modelech, modelování metodou konečných prvků.\n The presented heritage procedure was developed in 2018-2021 as part of the NAKI project no. DG18P02OVV040, entitled 'Monuments in Motion', funded by the Ministry of Culture of the Czech Republic. The basis for the design of this heritage procedure is the 30-year activity of Prof. Pirner, Ing. Urushadze and Ing. Bayer in the field of technical seismicity and building dynamics in general. The proposed heritage procedure is actually a methodological guide on how to proceed if there are any failures or negative effects that could be related to vibrations, as well as how to deal with them. For each of the various points of the procedure examples are given from our many years of practice. In general, these investigations involve theoretical and experimental analysis including in situ investigations, non-destructive and laboratory tests on models, using finite element modelling.\n
Keywords:
technical seismicity; modal analysis; measuring control panel; long-term monitoring; measuring shocks and movements; recorded data; frequency spectrum
Available in a digital repository NRGL
Ochrana památkových objektů proti vibracím
Předkládaný památkový postup byl vytvořen v letech 2018–2021 při řešení úkolu NAKI č. DG18P02OVV040, nazvaného 'Památky v pohybu', financovaného MK ČR. Podkladem pro vypracování ...
Výzkumná zpráva. Výzkum složení inkoustů v historické knize rentgenovou fluorescenční spektroskopií (XRF)
Vopálenský, Michal
2022 - Czech
V tomografu TORATOM v Centru Telč Ústavu teoretické a aplikované mechaniky, AVČR, byla provedena výpočetní tomografie (CT) vzácné knihy z Národní knihovny ČR – Slovanské knihovny. Jedná se o Euchologion, pocházející z Kyjeva ze 17. století. Během měření byla diskutována možnost měření složení inkoustů, kterými je kniha tištěna. Obecně se v knize vyskytují části tištěné černě a části tištěné červeně. Proto došlo k realizaci měření popisovaného v této zprávě, kde bylo změřeno několik stran díla v oblasti černého inkoustu, červeného inkoustu a v oblasti bez inkoustu. Computed tomography (CT) of a unique book from the National Library of the Czech Republic - Slavonic Library was performed in the TORATOM tomograph in Center Telč, Institute of Theoretical and Applied Mechanics, Czech Academy of Sciences. The book is a 17th century euchologion originating in Kiev. During the tomographic scanning, the possibility of measuring the composition of the inks used in the book was discussed. In general, there are parts printed in black and parts printed in red in the book. Therefore, the measurement described in this report was carried out, where several pages of the work were measured in the area of black ink, red ink and in the area without ink.
Keywords:
TORATOM; computed tomography (CT); Euchologion
Available at various institutes of the ASCR
Výzkumná zpráva. Výzkum složení inkoustů v historické knize rentgenovou fluorescenční spektroskopií (XRF)
V tomografu TORATOM v Centru Telč Ústavu teoretické a aplikované mechaniky, AVČR, byla provedena výpočetní tomografie (CT) vzácné knihy z Národní knihovny ČR – Slovanské knihovny. Jedná se o ...
Long term optical monitoring technique of displacement fields based on ArUco markers
Kunecký, Jiří
2022 - English
In structural engineering it is often needed to measure tiny displacements of parts of the structure extremely precisely. For such a purpose it is often needed to use some type of sensor attached to the surface of the structure. This paper presents a new technique which simply uses computer vision libraries to measure displacement of markers originally developed for robotics. Such analysis can be under specific circumstances (2D planar movement) valid if we compare two images taken at different times with the same camera. Main advantage of this method is simplicity of use and low cost of markers, which can be printed in a standard office laser printer. The resolution (error) can be for standard cameras around 0.1 pixel. The method is especially developed for research of timber frames/joints behavior in real structures, because displacements of joints in creep or under load can reach an amplitude which is perfectly detectable by this method.
Keywords:
displacement measurement; long-term monitoring; ArUco markers
Available at various institutes of the ASCR
Long term optical monitoring technique of displacement fields based on ArUco markers
In structural engineering it is often needed to measure tiny displacements of parts of the structure extremely precisely. For such a purpose it is often needed to use some type of sensor attached to ...
Zpráva o výsledcích chemické a mineralogické analýzy vzorku omítky z objektu: Zámek Opočno
Frankeová, Dita; Bauerová, Pavla; Slížková, Zuzana
2022 - Czech
V rámci stavebně-technického průzkumu byl proveden rozbor vzorků historických omítek s využitím termické analýzy a SEM‐EDS analýzy. Byla provedena charakterizace plniva a složek pojiva malt a jejich povrchových úprav. Výsledky průzkumných prací byly použity jako podklad pro návrh rekonstrukce objektu. An analysis of historical plaster was carried out using thermal analysis and SEM-EDS analysis. The binders and aggregates of mortars and their surface treatments were characterized. The survey results were used for the design of the repair mortars.
Keywords:
TGA; SEM/EDS; binder characterization
Available at various institutes of the ASCR
Zpráva o výsledcích chemické a mineralogické analýzy vzorku omítky z objektu: Zámek Opočno
V rámci stavebně-technického průzkumu byl proveden rozbor vzorků historických omítek s využitím termické analýzy a SEM‐EDS analýzy. Byla provedena charakterizace plniva a složek pojiva malt a jejich ...
Analysis of van der Pol equation on slow time scale for combined random and harmonic excitation
Náprstek, Jiří; Fischer, Cyril
2022 - English
Vortex shedding represents one of the most important processes that constantly attract the attention of experimental and theoretical research. A number of non-linear effects arise from the fluid-structure interaction. The non-stationary response in the vicinity of the lock-in region has a quasi-periodic character, beating frequency of which varies considerably with the distance from the lock-in frequency. This property is significantly affected by the assumption of combined random and harmonic excitation. This paper describes several details that contribute to the probabilistic characteristics of the system on a time-slow scale using partial response amplitudes.
Keywords:
SDOF oscillator; slow-time system; Fokker-Planck equation
Available at various institutes of the ASCR
Analysis of van der Pol equation on slow time scale for combined random and harmonic excitation
Vortex shedding represents one of the most important processes that constantly attract the attention of experimental and theoretical research. A number of non-linear effects arise from the ...
Construction of the Lyapunov function reflecting the physical properties of the model
Náprstek, Jiří; Fischer, Cyril
2022 - English
Practical experience shows that the random excitation component can affect the system response and its dynamic stability not only negatively but also positively. Such mechanisms are usually developed heuristically and are often not sufficiently justified theoretically. The paper presents a possibility of using the properties of first integrals for the construction of a Lyapunov function for the analysis of a dynamic system stability in the stochastic domain. In such case, the Lyapunov function itself contains information on the examined system and, consequently, it is able to provide a more detailed insight into the system stability properties. The procedure is illustrated by a nonlinear SDOF example.
Keywords:
Lyapunov function; stability; spherical pendulum
Available at various institutes of the ASCR
Construction of the Lyapunov function reflecting the physical properties of the model
Practical experience shows that the random excitation component can affect the system response and its dynamic stability not only negatively but also positively. Such mechanisms are usually developed ...
Zřícenina středověkého hradu a moderní technologie pro bezpečnou správu
Novotný, Jakub
2022 - Czech
Tématem příspěvku je vztah torzální architektury a moderních technologií. Nejprve je stručně představen dokument Report assessing innovative restoration techniques, technologies and materials used in conservation, který poskytuje přehled nejpoužívanějších technik, technologií a materiálů pro průzkumu a ochranu tohoto typu památek. Dále příspěvek přibližuje průběh a výsledky projektu regionální spolupráce Technologický výzkum zříceniny hradu Štamberk v širším kontextu regionu s důrazem na použití moderních technologií. The topic of the paper is the relationship between torsional architecture and modern technologies. First, the Report assessing innovative restoration techniques, technologies and materials used in conservation is briefly presented, which provides an overview of the most used techniques, technologies and materials for the exploration and protection of this type of monuments. Furthermore, the paper provides an overview of the progress and results of the regional cooperation project Technological research of the Štamberk castle ruins in the wider context of the region with an emphasis on the use of modern technologies.
Keywords:
ruin; modern technologies; Štamberk Castle; conservation
Available at various institutes of the ASCR
Zřícenina středověkého hradu a moderní technologie pro bezpečnou správu
Tématem příspěvku je vztah torzální architektury a moderních technologií. Nejprve je stručně představen dokument Report assessing innovative restoration techniques, technologies and materials used in ...
Analytical model of joint loaded perpendicular to wooden grain
Hataj, M.; Pošta, J.; Hasníková, Hana; Kunecký, Jiří
2022 - English
Computing models for structural behaviour and determination of traditional timber butt joints using analytical relations are presented in this paper. A component method is the base of the computing technique introduced herein. This method is usually used for steel joint design. The component method is based on dividing a joint into individual components. These are defined by partial joint component stiffness. An analytical solution includes a subsidence effect of wooden material close to compressive loading. Analytical computation results are compared with the experimental outputs. A design procedure according to Eurocode 5 for a load capacity determination of perpendicularly loaded structural elements is stated in the paper.
Keywords:
analytical models; load capacity; butt joint; carpentry; timber structures
Available at various institutes of the ASCR
Analytical model of joint loaded perpendicular to wooden grain
Computing models for structural behaviour and determination of traditional timber butt joints using analytical relations are presented in this paper. A component method is the base of the computing ...
Wooden construction of the movable roof of the garden pavilion in Český Krumlov castle
Bláha, Jiří; Kloiber, Michal
2022 - English
A remarkable technical monument is situated on one of the garden terraces belonging to the state castle and chateau in Český Krumlov. The umbrella-shaped roof of the lookout pavilion can be lifted about a meter above the masoned parapet allowing the visitor a beautiful view of the World Heritage town panorama when the weather is fine. In windy conditions or in case of heavy rain the roof could be lowered and the pavilion thus closed. The lifting is operated by means of a wooden lever mechanism with a counterweight box hidden in the basement level of the building. The unique construction was built in 1823 and needed to be partially altered in 1830-1835. However, since then it has been preserved in a surprisingly authentic state even allowing practical demonstrations of its original function. Prior to recent repairs in 2016, a comprehensive non-destructive survey was conducted. The extent of the damage discovered was determined by measuring the speed of elastic wave propagation using stress waves (Fakkop 2D) and measuring the mechanical resistance when drilling with a thin bit using resistance micro-drilling (Resistograph). Another method based on loading timber by means of a\nminiature loading jack inserted into a drilled hole was selected to determine the current mechanical properties.
Keywords:
lookout pavilion; gazebo; non-destructive testing; roof; timber; wood
Available at various institutes of the ASCR
Wooden construction of the movable roof of the garden pavilion in Český Krumlov castle
A remarkable technical monument is situated on one of the garden terraces belonging to the state castle and chateau in Český Krumlov. The umbrella-shaped roof of the lookout pavilion can be lifted ...
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