Number of found documents: 1087
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The Cloak Bridge in Český Krumlov – measuring of mechanical properties
Kloiber, Michal; Sebera, V.; Hrivnák, Jaroslav; Tippner, J.; Kunecký, Jiří
2017 - English
Timber bridges are often exposed to harsh conditions of the environment. The exposure of the timber structure often leads to its deterioration. Standard test procedures to determine typical properties of wood cannot be used as there is the requirement of the minimum interference with the structure. Several non-destructive testing (NDT) methods for the determination of timber condition have been developed and are used. However, the results of NDT can be used to predict mechanical properties of timber elements only to a limited degree. Semi-destructive testing (SDT) methods are a compromise. In the paper a functional model of a device that allows for the measurement of conventional strength and modulus of deformation of timber in compression parallel to the grain is presented. The device is inserted to a bored hole and pushes the jaws apart with a small test jack loading the bore walls. This paper presents possible use of the device for surveys of timber bridges. Keywords: model of device; mechanical properties Available at various institutes of the ASCR
The Cloak Bridge in Český Krumlov – measuring of mechanical properties

Timber bridges are often exposed to harsh conditions of the environment. The exposure of the timber structure often leads to its deterioration. Standard test procedures to determine typical properties ...

Kloiber, Michal; Sebera, V.; Hrivnák, Jaroslav; Tippner, J.; Kunecký, Jiří
Ústav teoretické a aplikované mechaniky, 2017

Chemický a mikroskopický rozbor vnější omítky, Petschkova vila, V sadech 2, Praha 6
Slížková, Zuzana; Viani, Alberto; Koudelková, Veronika; Frankeová, Dita; Hauková, Petra
2017 - Czech
Cílem práce bylo provedení analýzy malty z Petschkovy vily, byly navrženy analýzy XRD a SEM-EDX, jejichž výsledkem je charakterizace kameniva a pojiva malt. Pomocí analýz bylo určeno, že se jedná o sádrovou omítku s nátěrem. The aim of this work was to analyze mortar from Petschek villa, XRD and SEM-EDX analyzes have been proposed, which results in the characterization of aggregate and mortar binders. The analyses proved gypsum plaster with surface paint. Keywords: chemical composition; survey; material characterization; binder; aggregate Available at various institutes of the ASCR
Chemický a mikroskopický rozbor vnější omítky, Petschkova vila, V sadech 2, Praha 6

Cílem práce bylo provedení analýzy malty z Petschkovy vily, byly navrženy analýzy XRD a SEM-EDX, jejichž výsledkem je charakterizace kameniva a pojiva malt. Pomocí analýz bylo určeno, že se jedná o ...

Slížková, Zuzana; Viani, Alberto; Koudelková, Veronika; Frankeová, Dita; Hauková, Petra
Ústav teoretické a aplikované mechaniky, 2017

Chemické a mineralogické analýzy vzorků omítek ze SH Krakovec
Slížková, Zuzana; Frankeová, Dita; Hauková, Petra; Viani, Alberto
2017 - Czech
Pomocí mikroskopické analýzy, termické analýzy a XRD bylo určeno, že oba analyzované vzorky malty jsou malty vápenné s příměsí jílových minerálů. Obsažený písek v maltě je křemenný, jsou přítomna také zrna živců a slídy, struktura obou malt je odlišná. With using microscopic analysis, thermal analysis, and XRD, it was determined that both analyzed mortar samples are lime mortars with admixtures of clay minerals. The contained sand in the mortar is quartz, there are also grains of feldspar and mica, the structure of the two mortars is different. Keywords: chemical composition; survey; material characterization; binder; aggregate Available at various institutes of the ASCR
Chemické a mineralogické analýzy vzorků omítek ze SH Krakovec

Pomocí mikroskopické analýzy, termické analýzy a XRD bylo určeno, že oba analyzované vzorky malty jsou malty vápenné s příměsí jílových minerálů. Obsažený písek v maltě je křemenný, jsou přítomna také ...

Slížková, Zuzana; Frankeová, Dita; Hauková, Petra; Viani, Alberto
Ústav teoretické a aplikované mechaniky, 2017

Chemical and microstructural characterization of the render, sampled from the Garden wall of the US Embassy in Prague 1
Slížková, Zuzana; Frankeová, Dita; Viani, Alberto; Hauková, Petra; Koudelková, Veronika; Svoboda, Milan
2017 - English
The aim of the work was to analyze the mortar taken from the Garden wall (US Embassy, Prague 1). Analyzes were performed for the binder and filler characterization and the sample was also dissolved in HCl to determine the mixing ratio. Keywords: survey; material characterization; chemical composition; binder and aggregate characterization Available at various institutes of the ASCR
Chemical and microstructural characterization of the render, sampled from the Garden wall of the US Embassy in Prague 1

The aim of the work was to analyze the mortar taken from the Garden wall (US Embassy, Prague 1). Analyzes were performed for the binder and filler characterization and the sample was also dissolved in ...

Slížková, Zuzana; Frankeová, Dita; Viani, Alberto; Hauková, Petra; Koudelková, Veronika; Svoboda, Milan
Ústav teoretické a aplikované mechaniky, 2017

Microscopic features of cement paste modified by fine perlite
Hrbek, V.; Koudelková, Veronika; Padevět, P.; Šašek, Petr
2017 - English
The use of waste material and replacement of binder element in cementitious composites is in focus of material development. Perlite in the construction industry is usually used in form of lightweight aggregate enhancing the insulating performance of concrete. This paper focuses on integration of fine perlite into the cement matrix and possible replacement of the cement binder in the composition of the material. The macromechanical performance of the modified paste is tested on specimens with 5, 10, 15 and 20% fine perlite substitution and pure cement sample. To distinguish the effect of the perlite on the microstructural level, pure cement material and specimen containing 10% of fine perlite are investigated by the electron microscopy. Furthermore, the mechanical properties of individual phases are examined and compared on same samples by instrumented indentation. The presented results enabled estimation of fine perlite impact on the macro and microscopic performance of the material.. Keywords: perlite; SEM; nanoindentation; mechanical properties Available at various institutes of the ASCR
Microscopic features of cement paste modified by fine perlite

The use of waste material and replacement of binder element in cementitious composites is in focus of material development. Perlite in the construction industry is usually used in form of lightweight ...

Hrbek, V.; Koudelková, Veronika; Padevět, P.; Šašek, Petr
Ústav teoretické a aplikované mechaniky, 2017

Semi-automated assessment of micromechanical properties of the metal foams on the cell-wall level
Krčmářová, Nela; Šleichrt, J.; Doktor, T.; Kytýř, Daniel; Jiroušek, O.
2017 - English
Metal foams are innovative porous material used for wide range of application such as deformation energy or sound absorption, filter material, or microbiological incubation carrier. To predict mechanical properties of the metal foam is necessary to precisely describe elasto–plastic properties of the foam on cell–wall level. Indentation with low load is suitable tool for this purpose. In this paper custom designed instrumented microindentation device was used for measurement of cell-wall characteristics of two different aluminium foams (ALPORAS and ALCORAS). To demonstrate the possibility of automated statistical estimation of measured characteristics the device had been enhanced by semi-automatic indent positioning and evaluation procedures based on user-defined grid. Vickers hardness was measured on two samples made from ALPORAS aluminium foam and one sample from ALCORAS aluminium foam. Average Vickers hardness of ALPORAS foam was 24.465 HV1.019 and average Vickers hardness of ALCORAS was 36.585 HV1.019.. Keywords: metal foam; Vickers hardness; cell-wall; indentation under low loads Available at various institutes of the ASCR
Semi-automated assessment of micromechanical properties of the metal foams on the cell-wall level

Metal foams are innovative porous material used for wide range of application such as deformation energy or sound absorption, filter material, or microbiological incubation carrier. To predict ...

Krčmářová, Nela; Šleichrt, J.; Doktor, T.; Kytýř, Daniel; Jiroušek, O.
Ústav teoretické a aplikované mechaniky, 2017

A concept for testing and monitoring of building structures – theoretical case study
Bayer, Jan
2017 - English
A mere comparison of measured and analytical deformations, natural frequencies and mode\nshapes provides us with just a small part of the information contained in the data, especially when component- level damage prevention is needed. The presented analysis studies in detail a few criteria for evaluation of measured data, with the example of simulated plane trusses in respect to the ultimate limit state. It demonstrates the high potential of a systematic approach, while combining several criteria, particularly when using simultaneous strain and deformation measurements, as it documents the proposed Relative Mode Difference (RMD) criterion. On the other hand, the study points out the major limitation of practical applications that is caused by unknown inherent uncertainties of various kinds, providing us with the incentive for further experimental research. Keywords: testing; monitoring; building structures; ultimate limit state; mode shapes; strains Available at various institutes of the ASCR
A concept for testing and monitoring of building structures – theoretical case study

A mere comparison of measured and analytical deformations, natural frequencies and mode\nshapes provides us with just a small part of the information contained in the data, especially when component- ...

Bayer, Jan
Ústav teoretické a aplikované mechaniky, 2017

Materiálový průzkum břidlicové krytiny pro účel památkové obnovy objektu Nové proboštství, nám. sv. Jiří č.p. 34, Pražský Hrad
Drdácký, Miloš; Slížková, Zuzana; Frankeová, Dita; Hasníková, Hana; Hauková, Petra; Koudelková, Veronika; Kozlovcev, Petr; Valach, Jaroslav; Wolf, Benjamin
2017 - Czech
Zpráva obsahuje výsledky studie zaměřené na materiálové vlastnosti historické břidlicové střešní krytiny a posouzení jejího stavu vzhledem k plánované obnově budovy. The report includes the results of the study focusing on the material properties of historical roofing slate tiles and assessment of the state regarding the planned building reconstruction. Keywords: slate tile; bending strength; freeze-thaw resistance Available at various institutes of the ASCR
Materiálový průzkum břidlicové krytiny pro účel památkové obnovy objektu Nové proboštství, nám. sv. Jiří č.p. 34, Pražský Hrad

Zpráva obsahuje výsledky studie zaměřené na materiálové vlastnosti historické břidlicové střešní krytiny a posouzení jejího stavu vzhledem k plánované obnově budovy....

Drdácký, Miloš; Slížková, Zuzana; Frankeová, Dita; Hasníková, Hana; Hauková, Petra; Koudelková, Veronika; Kozlovcev, Petr; Valach, Jaroslav; Wolf, Benjamin
Ústav teoretické a aplikované mechaniky, 2017

Lyapunov exponents – practical computation
Fischer, Cyril; Náprstek, Jiří
2017 - English
The Lyapunov exponents serve as numerical characteristics of dynamical systems, which measure possible divergence of nearby trajectories of the solution. In this way they express dependence of the dynamical system on initial conditions. However, the value of Lyapunov exponents consists in their ability to characterise deterministic chaos. The limiting process intrinsic in the definition of Lyapunov exponents, unfortunately, seriously complicates their computation. The short paper presents an overview of difficulties in numerical approaches to enumeration of Lyapunov exponents or at least the largest one and shows a promising method based on QR decomposition of the system Jacobian. Keywords: Lyapunov exponent; dynamical system; non-linear system Available at various institutes of the ASCR
Lyapunov exponents – practical computation

The Lyapunov exponents serve as numerical characteristics of dynamical systems, which measure possible divergence of nearby trajectories of the solution. In this way they express dependence of the ...

Fischer, Cyril; Náprstek, Jiří
Ústav teoretické a aplikované mechaniky, 2017

Numerical assessment of stability of the ball vibration absorber
Fischer, Cyril; Náprstek, Jiří
2017 - English
The ball vibration absorber (BVA) is in principle a heavy ball rolling inside a semi-spherical cavity. It is a convenient alternative to the usual pendulum-based dampers. The dynamics of the real ball absorber is significantly more complicated in comparison to the pendulum one. However, the numerical examination of the non-linear model of the BVA indicates that its resonance behaviour is similar to the spherical pendulum. Despite the theoretical differences, the resonance curves in both cases form similar patterns. It seems that detailed study of both separate cases can provide complementary results, whose parallels appear in the other model. Keywords: ball vibration absorber (BVA); non-linear model; resonance Available at various institutes of the ASCR
Numerical assessment of stability of the ball vibration absorber

The ball vibration absorber (BVA) is in principle a heavy ball rolling inside a semi-spherical cavity. It is a convenient alternative to the usual pendulum-based dampers. The dynamics of the real ...

Fischer, Cyril; Náprstek, Jiří
Ústav teoretické a aplikované mechaniky, 2017

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