Papers by Keyword: Experimental Research

Abstract: Experimental verification of global reliability of slender reinforced concrete columns from the regular concrete C45/55 and high performance concrete C70/85 was realized within the applied research of the Faculty of Civil Engineering at Slovak University of Technology in Bratislava (SUT). Production of test columns and samples was in cooperation with ZIPP Bratislava Ltd. Columns are designed in the way to collapse due to stability before the resistance of the critical cross-section is reached. The relative compression of concrete was scheduled about 1,5 ‰. For performed experimentally verified slender columns, the reliability of simplified and nonlinear design methods according to European standards was compared.

Abstract: This paper presents some results of theoretical and experimental investigations of composite steel-concrete columns with solid steel profiles - steel cores. Due to absence of simplified design method according to EN 1994-1-1 [1], design of these columns in practice is limited in general. Reasons for this are residual stresses in steel profile caused by fabrication process and limitation of strains in concrete. Recommendations have been determined for simplified design method according to EN 1994-1-1 for composite columns made of high strength concrete filled steel tube with central steel core. Results of experimental research on composite columns with the cross-section made of steel core covered by reinforced concrete are presented.

Abstract: The paper deals with formation and development of cracks up to the failure of two span post-tensioned concrete girder. It is focused on influence of different bond between prestressing units and surrounding grout. Monitored and analysed phenomena affected by different bond are as follows: crack initiation, crack spacing and crack width of the prestressed girder. Sources of analysis are results from experimental program focused on influence of oil based corrosion protection agents on bond of prestressing units. Two span post-tensioned girders were subjected to the loading in laboratory till the bending failure has occurred. Girders were in two cases prestressed with bonded tendons. Other two girders were post-tensioned with unbonded tendons and two girders with tendons with decreased bond, due to corrosion protection coatings. Girders have demonstrated different behaviour by loading regarding to the bond level of prestressing units. Experimental results are faced with the results of the theoretical calculation of crack width according to European standards.

Abstract: The aim of this work is conducting theoretical and experimental research of the processes and modes of high-temperature processing of steel slags for more complete extraction of the metal component. "FactSage" software complex (version 6.4) was used to execute the thermodynamic modeling of the processes occurring during the recovery of metals from steelmaking slags. The experimental research included experiments on solid-phase and liquid-phase recovery of slag samples at the temperatures of 1000 – 1500 °C. The results of thermodynamic modeling and experimental high-temperature slag processing allows speaking about the advisability of preliminary solid-phase recovery slag in the atmosphere of carbon monoxide with subsequent high-temperature (liquid phase) recovery to obtain separate metal fractions.

Abstract: The results of thermodynamic modeling and experimental studies are presented in this article. The aim of this work is to determine the conditions of silicon carbide crystals synthesis in the complex composition metal melts. The "FactSage" software was used for thermodynamic modeling. The phase diagrams, in the form of liquidus surfaces, allow determining the metal composition with minimum melting temperature and presenting the ranges of concentrations and temperatures for which the equilibrium product of the interaction between the components of the metal melt is silicon carbide. The results of experimental research confirmed the possibility of growing silicon carbide crystals in the complex metal melts at low temperatures. The results of the obtained sample of complex alloy examination (conducted with the scanning electron microscope JEOL JSM–6460LV with a energy dispersion spectrometer by "Oxford Instruments" used for performing qualitative and quantitative microprobe analysis) helped to reveal the crystals corresponding to SiC composition.

Abstract: In this paper, we submit an advanced solution for the optimization of the supercharging process in the engines that are experimentally researched on the test bench. This solution may be applied only to the engines set on the test bench, whose energy, economic or ecological performances require an impetus by the optimization of the supercharging process. Cutting-edge automatic equipment for the achievement of the supercharging process should be used, with a view to studying and improving the behaviour of the experimentally researched engines, depending on the intensity of the supercharging process. In this way, the parameters to be fulfilled by the supercharging aggregate, which will equip the internal combustion engine, during its exploitation, will be known.

Abstract: In a properly designed slab-column structure the failure of the floor should be signalled by cracks and significant and visible deflections of the floor in the spans. The paper presents two proposed ways of calculating a uniform loading causing the destruction of the central field of a typical slab-column structure. The values obtained in the limit state were compared with the value of the load obtained during the experimental research.

Abstract: A great advantage of computer calculations is the opportunity to map the whole floor, including the supporting beams, columns and walls, in one model, with the members fully cooperating with one another. In this way the need for strenuous compiling of the loads on supporting members and independent searching for extreme values becomes eliminated. As a separate part of a floor, in this case a beam appears occasionally. The mapping of a beam in a model can have various forms. The paper presents a comparison of the influence of the way in which a rib is modelled on the results of statistical calculations. As a reference point for substitute shell models a solid spatial model was adopted.

Abstract: The behaviour of reinforced concrete slab-column structures under the impact of accidental loading is very significant due to safety reasons. The failure of the support zone by punching and lack of proper structural integrity reinforcement can lead to a progressive collapse. However, the instructions on how to prevent such situations are not very detailed. According to the guidelines of standard EC2, the structural integrity reinforcement should be continuous throughout the length and consist of at least two bars above the column in every perpendicular direction. EC2 does not state the amount of necessary reinforcement. The article presents a theoretical model of calculation that permits a more detailed analysis of internal forces in reinforcing bars located directly above the column. Adopting a solution in the form of exact equations makes it possible to take into account the influence of a non-linear change of the bar rigidity and considerable deflections. The calculation model was verified on the basis of the results of experimental investigations. It enables to estimate the tensile force of the bar at which it is ruptured during the destruction of the support zone.

Abstract: Frequently, on the drawings of mechanical parts, only indications concerning the surface roughness parameter Ra and, relatively rarely, the surface roughness parameter Rz are included. However, the study of the machined surface roughness highlights the necessity to use yet other surface roughness parameters, in order to have a clearer image on the state of the machined surface. Some other surface roughness parameters possible to be used and presenting importance, without the parameters Ra and Rz, were highlighted. One took into consideration the possibility of measuring parameters Rsk and Rmr by means of the available surface roughness testers. Experimental researches of turning by applying the method of full factorial experiment were developed. As input factors in turning process, the cutting speed, the feed rate and the tool nose radius were used. The experimental results were mathematically processed, being determined empirical mathematical models that highlight the influence of certain input factors of turning process on the values of some surface roughness parameters characterized by a more restricted use