Number of found documents: 76
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Book of Abstracts. 18th Youth Symposium on Experimental Solid Mechanics
Kytýř, Daniel; Doktor, Tomáš; Zlámal, Petr
2023 - English
The YSESM symposium provides a forum for young researchers and engineers, PhD students and students dealing with subjects of experimental mechanics. The Symposium concentrates on current work in all areas of experimental research and its application in solid and fluid mechanics. The topic will particularly concern to: Conventional and Advanced Experimental Methods in Solid and Fluid Mechanics; Non-Destructive Testing and Inspection, Measurements in Material Science, Computer Assisted Testing and Simulation, Engineering Design Simulation, Hybrid Methods, Experimental Techniques – Numerical Simulation, Optical Methods and Image Processing, Measurements in Biomechanics, Sensor Techniques for Micro- and Nano-Applications, Measurement Methods for Forensic Engineering. Keywords: experimental mechanics; fluid mechanics; mechanics of solids Fulltext is available at external website.
Book of Abstracts. 18th Youth Symposium on Experimental Solid Mechanics

The YSESM symposium provides a forum for young researchers and engineers, PhD students and students dealing with subjects of experimental mechanics. The Symposium concentrates on current work in all ...

Kytýř, Daniel; Doktor, Tomáš; Zlámal, Petr
Ústav teoretické a aplikované mechaniky, 2023

Vhodné restaurátorské postupy pro zachování stop opracování kamene. Využití blízké fotogrammetrie k ohodnocení vhodnosti restaurátorských postupů
Cihla, Michal; Frommeltová, E.; Hodač, J.; Kovářová, K.; Pavelka, K.; Panáček, M.; Valach, Jaroslav
2023 - Czech
Tento památkový postup je výsledkem výzkumného projektu s názvem „Topografie povrchu kamene a její aplikace v oblasti restaurování kamenných prvků“ č. DG20P02OVV021, podpořeném Ministerstvem kultury ČR. Cílem památkového postupu bylo ověření vhodnosti a použitelnosti přesných měřičských metod za účelem zhodnocení míry restaurátorského zásahu v oblasti stop po opracování povrchu kamene. Nástrojem pro hodnocení změn topografie kamenných povrchů nesoucích stopy po opracování byla zvolena metoda blízké fotogrammetrie. This preservation procedure is the result of the research project entitled „Building stone surface topography and its application in the field of stone features restoration“ No.DG20P02OVV021, supported by the Ministry of Culture of the Czech Republic. The aim of the preservation procedure was to verify the suitability and applicability of precise measuring methods in order to assess the degree of restoration intervention in the area of traces of stone surface working. The method of close-range photogrammetry was chosen as a tool to evaluate the changes in the topography of stone surfaces bearing traces of working. Keywords: stone topography; photogrammetry; stonemason’s tools traces; restoration; conservation; stone; monuments; building stone Fulltext is available at external website.
Vhodné restaurátorské postupy pro zachování stop opracování kamene. Využití blízké fotogrammetrie k ohodnocení vhodnosti restaurátorských postupů

Tento památkový postup je výsledkem výzkumného projektu s názvem „Topografie povrchu kamene a její aplikace v oblasti restaurování kamenných prvků“ č. DG20P02OVV021, podpořeném Ministerstvem kultury ...

Cihla, Michal; Frommeltová, E.; Hodač, J.; Kovářová, K.; Pavelka, K.; Panáček, M.; Valach, Jaroslav
Ústav teoretické a aplikované mechaniky, 2023

Innovative device for the simulation of environmental conditions and testing of building materials
Cacciotti, Riccardo; Wolf, Benjamin; Macháček, Michael; Frankl, Jiří
2022 - English
Excessive humidity influences the performance of building envelopes and the safety of their occupants. Moisture related problems can indeed impose significant health risks for buildings’ users and even lead, under extreme scenarios, to structural failures. This paper investigates an innovative experimental setup for evaluating the influence of changing environmental conditions on the performance of building materials. It stems out from a broader ongoing research aimed at studying the trends of mould growth on wooden building components. The presented results include the design, construction and numerical validation of a small-scale climatic wind tunnel (2m x 1.8m ca.) to be used for the simulation of natural ventilation and daily humidity and temperature fluctuations. Key findings include the final design of a low cost, modular construction which allows gathering reliable data on the response of building materials exposed to changing boundary conditions, intended for improving current mould growth models. Future work is also suggested. Keywords: building envelope; moisture; building material; wind tunnel; performance Available in digital repository of the ASCR
Innovative device for the simulation of environmental conditions and testing of building materials

Excessive humidity influences the performance of building envelopes and the safety of their occupants. Moisture related problems can indeed impose significant health risks for buildings’ users and ...

Cacciotti, Riccardo; Wolf, Benjamin; Macháček, Michael; Frankl, Jiří
Ústav teoretické a aplikované mechaniky, 2022

Application of first integrals in the construction of the Lyapunov function for the random response stability testing
Náprstek, Jiří; Fischer, Cyril
2022 - English
The paper deals with a possibility of using the properties of first integrals for the construction of Lyapunov function for the analysis of a dynamic system stability in the stochastic domain. It points out certain characteristics of first integrals resulting in the necessity to introduce additional constraints to assure the principal properties of the Lyapunov function. A number of these constraints has their physical interpretation with reference to system stability. The advantage of this method constructing the Lyapunov function consists in the fact that the Lyapunov function itself contains information on the examined system and, consequently, it is not merely a positive definite function without any relation to the actual case concerned. The presented theory finds application in many dynamical systems. The procedure is illustrated by a nonlinear SDOF example. Keywords: stochastic stability; Lyapunov function; first integrals; cyclic coordinates Available in digital repository of the ASCR
Application of first integrals in the construction of the Lyapunov function for the random response stability testing

The paper deals with a possibility of using the properties of first integrals for the construction of Lyapunov function for the analysis of a dynamic system stability in the stochastic domain. It ...

Náprstek, Jiří; Fischer, Cyril
Ústav teoretické a aplikované mechaniky, 2022

Determination of aerodynamic coefficients for air flow around U-profiles with different flange porosities
Ledvinková, Blanka; Hračov, Stanislav; Macháček, Michael
2022 - English
Our contribution presents the comparison of the experimental investigations and of the numerical 2D simulations of the air flow around U –profiles having different flange porosities. The U-shaped beams were exposed to the air flow having a given velocity at different angles of the wind attack for obtaining the curves of the aerodynamic coefficients depending on the impact angle. The numerical simulations of the wind tunnel testing were performed using the Unsteady Reynolds Averaged Navier-Stokes (RANS) method, k-ω SST turbulence model was assumed. Keywords: U-shaped beams; porosity; wind tunnel; RANS simulation; k-ω SST model Available in digital repository of the ASCR
Determination of aerodynamic coefficients for air flow around U-profiles with different flange porosities

Our contribution presents the comparison of the experimental investigations and of the numerical 2D simulations of the air flow around U –profiles having different flange porosities. The U-shaped ...

Ledvinková, Blanka; Hračov, Stanislav; Macháček, Michael
Ústav teoretické a aplikované mechaniky, 2022

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 ...

Náprstek, Jiří; Fischer, Cyril
Ústav teoretické a aplikované mechaniky, 2022

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 ...

Urushadze, Shota; Pirner, Miroš; Bayer, Jan
Ústav teoretické a aplikované mechaniky, 2022

Aerodynamic interference forces acting on two square prisms in a model atmospheric boundary layer
Macháček, Michael; Lo, Y. L.; Máca, J.
2022 - English
The presented experimental analysis focuses on the definition of interference factors for aerodynamic forces acting on two square prisms depending on their relative position. Both prisms used had the same dimensions and a height to width ratio of 6 - this ratio is relatively common in high-rise buildings. The experiment was performed in a wind tunnel with a model atmospheric boundary layer, which represented a dense urban area. The forces acting at the base of one of the buildings were measured, and by moving the other building it was possible to measure 204 mutual configurations, i.e., 204 interference positions. In all positions, the windward facades of the small-area model were placed perpendicular to the direction of the incoming flow. This created a detailed map of the interference effect on a wind-loaded pair of buildings. The results show a significant effect of the relative position of buildings on wind loads. A significant increase in\nload occurred due to the proximity of buildings. Due to the interference effect, wind load fluctuations can increase by up to 28% and average values by up to 36%. Keywords: interference effect; two square prisms; wind tunnel experiments; turbulent boundary layer Available in digital repository of the ASCR
Aerodynamic interference forces acting on two square prisms in a model atmospheric boundary layer

The presented experimental analysis focuses on the definition of interference factors for aerodynamic forces acting on two square prisms depending on their relative position. Both prisms used had the ...

Macháček, Michael; Lo, Y. L.; Máca, J.
Ústav teoretické a aplikované mechaniky, 2022

Tomographic investigation of the sandstone fracture toughness
Vavřík, Daniel; Beneš, Pavel; Fíla, Tomáš; Koudelka_ml., Petr; Kumpová, Ivana; Vavro, Martin
2022 - English
It is well known that the measured values of the fracture toughness of quasi brittle materials are influenced by material heterogeneity, dimensions, boundary conditions, and unequal tension and compression properties. Standard testing methods supposing isotropic material, in contrary the quasi-brittle materials differ from this theoretical expectation, therefore this approach may fail. The authors present Local Fracture Toughness Testing (LFTT) method to overcome this obstacle. LFFT based on a complex methodology using a series of tomographic reconstructions recorded during specimen loading is calculated independently of the outside boundary conditions. Keywords: fracture process zone; crack path; quasi-brittle material; X-Ray computed tomography; four-point bending test Available in digital repository of the ASCR
Tomographic investigation of the sandstone fracture toughness

It is well known that the measured values of the fracture toughness of quasi brittle materials are influenced by material heterogeneity, dimensions, boundary conditions, and unequal tension and ...

Vavřík, Daniel; Beneš, Pavel; Fíla, Tomáš; Koudelka_ml., Petr; Kumpová, Ivana; Vavro, Martin
Ústav teoretické a aplikované mechaniky, 2022

Výběr vzorků malt pro radiouhlíkové datování
Válek, Jan; Kozlovcev, Petr; Fialová, Anna; Kotková, Kristýna; Frankeová, Dita; Skružná, Olga; Maříková-Kubková, Jana; Tomanová, Pavla; Herichová, Iva; Světlík, Ivo; Pachnerová Brabcová, Kateřina; Šimek, Pavel
2022 - Czech
Radiokarbonové datování organických zbytků nemusí vždy správně vypovídat o stáří analyzované historické malty. Proto se zdá výhodné využití možnosti datace uhlíku obsaženého ve struktuře vápenné malty, který při správném zpracování poskytne reprezentativní údaje o době vzniku studované konstrukce. Metodika představuje základní návod pro výběr vzorků, jejich zpracování a vyhodnocení. Cílem metodiky je identifikace případů, kdy je radiouhlíková datace pojiva vhodná a vymezení důvodů proč se u některých pojivových systémů nedaří získat relevantní výsledky. Radiocarbon dating of organic residues may not always correctly determine the age of analysed historic mortars. Therefore, it seems advantageous to use of carbon dating of the carbon contained in the structure of the lime mortar, which will provide representative data of the age of the investigated structure. The methodology presents basic instructions and rules for sample selection, processing, and evaluation. The aim of this methodology is the identification of cases where the radiocarbon dating of a binder is appropriate and to define the reasons why some binder systems fail to provide relevant results. Keywords: historic binders; mortars; radiocarbon Available in a digital repository NRGL
Výběr vzorků malt pro radiouhlíkové datování

Radiokarbonové datování organických zbytků nemusí vždy správně vypovídat o stáří analyzované historické malty. Proto se zdá výhodné využití možnosti datace uhlíku obsaženého ve struktuře vápenné ...

Válek, Jan; Kozlovcev, Petr; Fialová, Anna; Kotková, Kristýna; Frankeová, Dita; Skružná, Olga; Maříková-Kubková, Jana; Tomanová, Pavla; Herichová, Iva; Světlík, Ivo; Pachnerová Brabcová, Kateřina; Šimek, Pavel
Ústav teoretické a aplikované mechaniky, 2022

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