No (522)
Used filters
(4)
Number of found documents:
522
Published from
to
Micro-mechanical performance of concrete used as recycled raw material in cementitious composite
Hrbek, Vladimír; Koudelková, Veronika; Prošek, Z.; Tesárek, P.
2017 - English
The reduction of industrial pollution is recently one of main goals over all fields. In civil engineering, re-cycling of structural waste provides wide opportunity contributing this effort. This paper focus on re-use of concrete waste, which after further processing can be used in new constructions as partial supplement to the mixture. To investigate the impact of re-cycled concrete addition, it is necessary to determine mechanical and structural parameters of individual phases in the “raw” material. For this purpose, grid indentation and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM, EDX) are combined to determine properties of concrete sample.
Keywords:
re-cycled concrete; grid indentation; SEM; EDX; image analysis
Available at various institutes of the ASCR
Micro-mechanical performance of concrete used as recycled raw material in cementitious composite
The reduction of industrial pollution is recently one of main goals over all fields. In civil engineering, re-cycling of structural waste provides wide opportunity contributing this effort. This paper ...
Triangulated medieval cities
Loits, André; Drdácký, Tomáš; Buzek, Jaroslav; Zadražil, Tomáš
2017 - English
The paper presents a long term research work addressing sometimes not so evident values of historic cities, which are linked with geometric (urban) relations between the architectural elements set in cities. the position of city boundary (walls), market place and street layout was an intentional concept, not a result of unorganized building activities of new colonists. It is known from the archive and historic data, and verified by archaeological findings that the founded cities were planned. It is evident that cities seemingly different are organized following certain rules and methods. The work supports the hypothesis that original concept of the city survived in its pattern and structure until today and is one of the values expressing its individual and original identity. Hypothetic Medieval triangulation method, developed by André Loits is presented on case studies of České Budějovice, Kadaň and Klatovy. The method was so far used for the analysis of 30 selected Town Heritage Reserves and Zones and identifies two basi 'schools' in location concepts of studied cities.
Keywords:
historic cities; location; medieval triangulation; urban pattern; urban heritage values
Available at various institutes of the ASCR
Triangulated medieval cities
The paper presents a long term research work addressing sometimes not so evident values of historic cities, which are linked with geometric (urban) relations between the architectural elements set in ...
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 ...
Freeze-thaw durability of fiber-reinforced lime-based mortars
Přinosil, Michal
2016 - English
This paper presents results of experimental investigation focused on freeze-thaw\ndurability of fiber-reinforced lime-based mortars. Evolution of structural deterioration and frost resistance were evaluated using non-destructive testing (resonance method). In this study, we consider two types of lime-based matrices (pure lime, lime-metakaolin) and two types of polyvinyl alcohol fibers in several volume fractions. The results showed that the resistance against the frost depends mainly on the matrix type and on the amount of fibers.
Keywords:
freeze-thaw durability; lime-based mortar; fiber composite; fiber reinforcement
Available at various institutes of the ASCR
Freeze-thaw durability of fiber-reinforced lime-based mortars
This paper presents results of experimental investigation focused on freeze-thaw\ndurability of fiber-reinforced lime-based mortars. Evolution of structural deterioration and frost resistance were ...
Cross-section analysis and mapping using Raman spectroscopy
Majtás, Dušan; Mácová, Petra; Kreislová, Kateřina
2016 - English
When dealing with corroded objects, it is necessary to identify the corrosion products to develop a proper treatment for this particular object. Using X-ray diffraction is still suitable to do the phase composition analysis of the material; however it does the analysis of the material in bulk. It is also possible to use SEM to analyze the structure of the corrosion layers on a cross-section by EBSD method; however this method is time consuming. It is more suitable to use Raman spectroscopy when studying the structure of corrosion layers. Using proper equipment, such as Raman microscope it is possible to do not only analysis of precisely given point, but it is also possible to do mapping (both 1D and 2D) of the cross-section. Taking map of surface also does need time, but is definitely less time consuming compared to EBSD method.
Keywords:
corrosion; cross-section; mapping; micro-Raman spectroscopy
Available at various institutes of the ASCR
Cross-section analysis and mapping using Raman spectroscopy
When dealing with corroded objects, it is necessary to identify the corrosion products to develop a proper treatment for this particular object. Using X-ray diffraction is still suitable to do the ...
Vibration analysis of visco-elastically coupled beams
Hračov, Stanislav; Náprstek, Jiří
2016 - English
The paper presents a detail analysis of the forced vibration. The dynamic behaviour of the system is investigated parametrically to cover all possible effects of individual subsystems. Damping effectiveness is also analysed for several values of viscosity of the interlayer and damping of the particular beams. The recommendations and limitations for the application of the system are presented and discussed.
Keywords:
vibrations; dynamic analysis; damping
Available at various institutes of the ASCR
Vibration analysis of visco-elastically coupled beams
The paper presents a detail analysis of the forced vibration. The dynamic behaviour of the system is investigated parametrically to cover all possible effects of individual subsystems. Damping ...
Non-linear normal modes in dynamics-continuous systems
Náprstek, Jiří; Fischer, Cyril
2016 - English
The paper presents a continuation of an effort started last year, when the authors briefly informed about the Non-linear normal modes (NNM) concerning the version dealing with discrete systems. Although many features of the continuous formulation from the mathematical viewpoint are similar to the discrete case, a couple of specifics should be highlighted from the viewpoint of a real applicability of this tool to investigate particular dynamic systems. Three approaches are mentioned in the paper and the Galerkin-Petrov based procedure is outlined in more details. As a particular subject the cantilever prismatic beam is discussed. Non-linear normal modes for several amplitudes are shown to demonstrate the dependence of their shapes on the actual effective amplitude. Comparison with adequate linear counterpart is done.
Keywords:
nonlinear dynamic systems; non-linear normal modes; discretization; multi-scale method
Available on request at various institutes of the ASCR
Non-linear normal modes in dynamics-continuous systems
The paper presents a continuation of an effort started last year, when the authors briefly informed about the Non-linear normal modes (NNM) concerning the version dealing with discrete systems. ...
Experiment E7/0,3-displacement processes in non cohesive sand mass during active translative motion of retaining wall
Koudelka, Petr
2016 - English
The first part of information on the new experiment denominated as E7/0,3 with active pressure of non-cohesive quartz sand on time behaviour of the mass was presented at the last Conference (P. Koudelka, 2015). The second part is object of this Paper. The experiment was performed at the Institute of Theoretical and Applied Mechanics in 2014. The moved rigid front wall of the experimental equipment was translatively moved towards active direction (out of the mass) at a position of supposed acting of active pressure value, then the wall motion was stopped and time pressure stability was monitored. After more than three months the wall was moved at the last position of 100 mm from original position before the experiment. The experiment ran four and a half months. The paper presents firstly results on the deforming mass through the course of the wall movement at a supposed position for active pressure mobilization of 1.357 mm and after the further movement. The experiment was repeated to be the results proved (Experiment E8/0,3). New results are analysed.
Keywords:
retaining wall; active lateral earth pressure; non-cohesive material; sandy mass behaviour; wall movement modus; displacements
Available on request at various institutes of the ASCR
Experiment E7/0,3-displacement processes in non cohesive sand mass during active translative motion of retaining wall
The first part of information on the new experiment denominated as E7/0,3 with active pressure of non-cohesive quartz sand on time behaviour of the mass was presented at the last Conference (P. ...
Determination of thermal response of Carrara and Sneznikovsky marble used as building material
Petráňová, Veronika; Valach, Jaroslav; Viani, Alberto; Pérez-Estébanez, Marta
2016 - English
Physical weathering of marble, widely used as a cladding material on buildings, is one of the most common damaging mechanism caused by anisotropic thermal expansion of calcite grains. The extent of marble deterioration depends mainly on stone fabric and texture. Dry cuboids of Carrara marble and marble from Dolni Morava quarry were subjected to microscopic analysis and thermal cycling, to determine the thermal expansion related to stone fabric and predominant lattice orientation of grains (i.e. texture).
Keywords:
marble; anisotropic thermal expansion; thermal dilatation
Available at various institutes of the ASCR
Determination of thermal response of Carrara and Sneznikovsky marble used as building material
Physical weathering of marble, widely used as a cladding material on buildings, is one of the most common damaging mechanism caused by anisotropic thermal expansion of calcite grains. The extent of ...
Investigation of aeroelastic bridge instabilities using the multidimensional Fokker-Planck equation and wind-tunnel experiment
Král, Radomil
2016 - English
Stability of bridges and other line-like engineering structures is an important part of their overall design. It is also still of great interest nowadays due to a higher demand on increasing the span while maintaining an economical cost and service. During the previous decades sophisticated methods for the aeroelastic instability prediction have evolved and successfully applied to the real structures and many questions have been adequately answered.
Keywords:
aeroelastic instability; Fokker-Planck equation; wind-tunnel; bridges
Available at various institutes of the ASCR
Investigation of aeroelastic bridge instabilities using the multidimensional Fokker-Planck equation and wind-tunnel experiment
Stability of bridges and other line-like engineering structures is an important part of their overall design. It is also still of great interest nowadays due to a higher demand on increasing the span ...
NRGL provides central access to information on grey literature produced in the Czech Republic in the fields of science, research and education. You can find more information about grey literature and NRGL at service web
Send your suggestions and comments to nusl@techlib.cz
Provider
Other bases