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- ItemA comparative study on the applicability of six radiant floor, wall, and ceiling heating systems based on thermal performance analysis(ELSEVIER, 2021-04-01) Oravec, Jakub; Šikula, Ondřej; Krajčík, Michal; Arici, Müslüm; Mohapl, MartinHolistic comparisons of radiant heating systems that would help make an informed decision on the selection of the most convenient system for the specific application are lacking. The applicability of six representative radiant floor, wall, and ceiling heating systems was therefore compared in terms of thermal output and surface area required, controllability, short-term and long-term heat storage, suitability for building retrofit, and investments. Temperature and heat flux distribution in the structure, time constant tau(63), response time tau(90), and the number of operating cycles were computed by a custom-made and verified software tool using the finite volume method. Thermal energy stored was used to determine the ability of energy storage, whereas investment costs indicated affordability. Wall heating with pipes attached to a thermally insulating core had the highest thermal output, was easy to control, suitable for building retrofit, and most affordable while providing limited thermal storage. The performance of the wall system was retained when locating the pipes in plasterboard separated from the core by an air gap. Floor heating performed consistently in all the aspects evaluated. It was demonstrated that inserting a metal fin between pipes and the concrete spread layer improved thermal output, controllability, and storage capacity of the floor system with minor effect on investments. Ceiling with pipes insulated from the core performed well when thermal storage was not required. Ceiling with pipes embedded in the core was only feasible when long-term heat storage was needed.
- ItemNumerical Modelling of Slope Instability(Elsevier, 2015-11-07) Chalmovský, JurajThis article is dealing with stability of the highway cut in Eastern Slovakia. The cut is situated in rock environment of the Carpathian flysch, which in area of the cut mostly consists of shale with different degree of weathering. The cut is supported by an anchored pile wall. Rock environment is changing from the surface to the depth from alluvium clays, sands and completely weathered shale to fresh shale. The potential slip surface was investigated after evaluation of data from geotechnical monitoring, so stability of the pile wall has to be analyzed. Finite element analysis was done and two material models were compared to results of geotechnical monitoring. Deformation analysis and the safety factor are discussed. Two models were compared in these terms: Mohr - Coulomb material model and jointed rock material model. These models are introduced because of shale anisotropy and simplification of behavior model via jointed rock model. Jointed rock model was introduced as an anisotropic model and required geotechnical parameters for calculations are discussed in comparison with the Mohr – Coulomb material model. Anisotropic behavior of shale will be discussed and analyzed. Short recommendations for the use of these models are presented in the paper.
- ItemExperimental study on time dependent behaviour of coarse aggregate concrete mixture for 3D construction printing(Elsevier, 2023-04-20) Vespalec, Arnošt; Podroužek, Jan; Boštík, Jiří; Miča, Lumír; Koutný, DanielThis experimental study analyses coarse aggregate-containing and coarse aggregate-free materials from the perspective of additive manufacturing. The primary objective is to identify, through a series of experiments, the fundamental equations that characterise material behaviour at early ages in order to formulate a digital material model. During the research, a previously unreported phenomenon, namely the contradictory development of Young's modulus and cohesion, was observed. In addition, the sensitivity of buildability to changes in material properties was discussed and demonstrated with a motivating example using a spatiotemporal simulation of 3Dprinted concrete.
- ItemEnergy-Pile Model Verification(KGH, 2020-12-31) Šikula, Ondřej; Slávik, Richard; Eliáš, Jan; Oravec, Jakub; Kašpar, AntonínEquipping the foundation piles with a liquid circuit pipeline makes it possible to use the advantageous thermal capacity of the soil for heating and cooling buildings at low cost. The energy performance of the energy-pile in a soil is a transient phenomenon dependent on many parameters, which could be investigate by a computational model. The contribution deals with the description and verification of a new numerical computational software based on a simpli-fied 2D and 2D rotational symmetrical heat conduction model being developed for energy-piles modeling.
- ItemStatistical Estimate of Uniaxial Compressive Strength of Rock Based on Shore Hardness(Elsevier, 2017-06-20) Závacký, Martin; Štefaňák, Jan; Horák, Vladislav; Miča, LumírThe paper presents the use of advanced stochastic simulation techniques for estimating the strength behavior of rock materials. The Shore Rebound hardness was measured on fifty rock specimens coming from eleven different geological localities in Czech Republic. The dry unit weight of every tested rock material was determined also. Uniaxial compressive strength of rock was evaluated then by conducting the compression test on every specimen. Empirical distribution of Shore hardness and dry unit weight variables obtained from laboratory tests was approximated by the best fitted theoretical probability distribution. The stochastic simulation using Latin Hypercube Sampling was conducted based on those distributions. Two different equations used for estimating the compressive strength of rock on the basis of Shore hardness in practice was used as model functions. Comparison and statistical evaluation of uniaxial compressive strength of rock determined by compression test and those obtained as a result of stochastic simulation is discussed. The description of probability distribution of uniaxial strength is obtained as a result of introduced analysis, which can be used as input for fully probabilistic design models of rock materials.