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RESEARCH AND DEVELOPMENT COMPOSITE MATERIAL WITH A HIGHER RESISTANCE TO HIGH TEMPERATURES
Válek, Jaroslav ; Durica,, Tibor (referee) ; Kolář,, Karel (referee) ; Sitek,, Libor (referee) ; Bodnárová, Lenka (advisor)
Concrete has many advantageous properties as regards resistance to fire. It is non-flammable and it has a low thermal conductivity. However, concrete structures, which are not designed for resistance against fire, show significant damage after heating. In particular, the explosive flaking with the consequence of weakening the reinforced concrete cross-section and exposing the steel reinforcement to the temperatures higher than critical temperature of reinforcement. There are only a few possible measures of preventing or mitigating the effects temperature load used. Ways of protection can be divided into two systems: active and passive. Active systems are designed to ensure the greatest possible reduction of temperatures the concrete is exposed to. Passive systems directly resist to high temperatures and fire. Design of composition of concrete with the aim of higher resistance to exposition to high temperatures belongs among the passive systems. A part of the work focuses on summary searches of the problems of concrete and reinforced concrete structures exposed to high temperatures and fire. The goal of the work is defining requirements for cement matrix based composite material and its design ensuring the highest possible resistance to high temperatures or direct fire.
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Design of the Timber-Concrete Composite Ceiling Structure
Válek, Jakub ; Horák, David (referee) ; Švaříčková, Ivana (advisor)
The reconstruction of existing houses is currently a frequent issue. This work deals with the possibilities of reinforcing wooden ceilings with the focus on ceiling reinforcement using an over concrete slab. This suggested ceiling reconstruction work is desirable from the point of view of the rigidity of the object in the horizontal direction. The work includes the proposition for the composite, according to various norms and their comparison regarding the economic side of the design. The work further provides a description of the experiment, its preliminary results and its comparison with the theoretical calculation.
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Optimalization of Mikulovice st. hr. - Hanušovice railway track, km 20,6 - km 23,3
Válek, Jiří ; Wrana, Radim (referee) ; Hruzíková, Miroslava (advisor)
The bachelor thesis deals with design of recontruction of the railway line Mikulovice st. hr. – Hanušovice in section from km 20,6 to km 23,3, that is located between stations Ostružná - Horní Lipová. The object of this thesis is improvement of the track geometry parameters, reconstruction of the railway superstructure and substructure, renewal of the drainage and elaboration of the bill of quantities.
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Economic Design of Concrete Slab of Administration Building
Válek, Jakub ; Klodner, Jan (referee) ; Perla, Jan (advisor)
The economic cost of a static design is nowadays very often the decisive factor during a tender. This work deals with the economic cost of designing the ceiling construction of a polyfunctional building. The work shows three design options regarding the second boundary condition. The decisive factor is the deflection under the masonry constructions. The deformation of the ceiling construction cannot be allowed to cause cracks in the masonry partitions. The aim of this work is the comparison of the economic cost of the possible design options.
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Design of magnetorheological damper with asymmetric velocity characteristic
Válek, Josef ; Macháček, Ondřej (referee) ; Kubík, Michal (advisor)
This thesis aims to find optimal solution for magnetorheological damper with asymmetric force-velocity behaviour. Magnetorheological dampers represent a promising direction in the development of vibration dampers, mainly due to their adjustable damping, that depends on electric current. The asymmetric force-velocity behaviour (characteristic) then means difference while compressing or expanding damper and can be achieved by valves. Valves can be solved in mechanical, hydraulic, magnetic, electric way. This bachelor´s thesis evaluates these four ways of solution and develops conceptual solutions for their possible application. One conceptual solution is then elaborated in detail. Chosen mechanical solution with movable plate was verified by calculations and experiment. Experiments confirmed the applicability of a mechanical valve in magnetorheological systems.
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Magnetorheological fluid response time in shear mode
Válek, Josef ; Vimmr, Jan (referee) ; Kubík, Michal (advisor)
Magnetorheological fluids (MRF) are suspensions of (commonly) oils and carbonyl iron powder. Under magnetic field, apparent viscosity of suspension changes in short time. This so-called response time can’t be neglected in modern MR devices. Multiple response times are distinguished based on load mode. Rheological response time (MRF under shear rate) will be affected by load and composition of MRF. In this thesis, these influencing parameters are investigated, which was allowed by developing rheometer with minimal hardware response time and methodology. Gained data shows, that most affecting parameter is ratio of inner forces, described e.g., Mason number. Model of Mason number was verified for larger values, but in lower values, significant difference was observed (probably caused by different shear stress mechanism in MRF). After other investigation and clarification of model, precise prediction of MRF and MR devices behaviour will be possible, which can lead to improving their function and e.g., road safety.
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Monitoring the condition of the archaeological sites of Prague Castle
Válek, Jan ; Kozlovcev, Petr ; Kotková, Kristýna ; Fialová, Anna ; Svorová Pawełkowicz, Sylwia ; Frankl, Jiří
In order to study microclimatic conditions, monitoring of selected archaeological terrains of Prague Castle was carried out in the period from August 2020 to May 2023. The internal climate of the area under the third courtyard of Prague Castle, also called Great Excavations, was monitored in the given time range. During the monitoring campaign, sensors were also placed in the area of the Small Excavations and the archaeological terrain of St. George's Monastery at various times. In particular, relative humidity, air and materials temperatures, moisture content of building materials, etc. were monitored. Samples of building materials were also taken and analysed, and the presence of biological degradation agents was monitored. The research focused in detail on describing the temperature and relative humidity of the indoor environment in relation to the moisture content of the materials and their potential degradation agents. These are primarily represented here by water-soluble salts. Their hazardousness in terms of damage to historic materials is influenced by variations in relative humidity and evaporation of water from capillary pores in combination with temperature. Research has shown that the most significant problem for sites is flooding or water seepage through the ground, surrounding structures or ceiling.
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Space Exploration of Mars
Válek, Jiří ; Sedláček, Pavel (referee) ; Froehling, Kenneth (advisor)
Tato bakalářská práce shrnuje minulé a současné mise k Marsu a uvádí objevy, úspěchy a technologie použité během jednotlivých misí. První kapitola se zaměřuje na první průzkumné mise Sovětského svazu a Spojených států během studené války a popisuje důležité úspěchy jednotlivých misí. Dále tato práce pojednává o roverech, jako jsou Opportunity, Spirit, Curiosity a také o Perseverance, které byly navrženy pro mobilní průzkum povrchu planety. Poslední část této práce se zabývá možností vyslání lidské posádky na tuto planetu, stavbou habitatů a samotnou cestou mezi Zemí a Marsem. V této kapitole jsou také nastíněna zdravotní rizika a různé problémy, kterým by posádka během takové mise musela čelit.
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