Communications - Scientific Letters of the University of Zilina, 2002 (vol. 4), issue 3
Articles
Modeling and BEM Analysis of Reinforced Concrete Cracked Panels
Maciej Yan Minch
Communications - Scientific Letters of the University of Zilina 2002, 4(3):5-8 | DOI: 10.26552/com.C.2002.3.5-8 
In this paper the method of distribution solution of RC (reinforced concrete) cracked of the plane stress plates (panels) is shown. The viscoelastic RC cracked plate model has been derived by the variation method of Gurtin in the class of the general function. The total differential equations in the two-dimensional general vector functions are shown. In this model the effect of the discontinuity general deformation vector, bond slip and concrete creep are taken into account. The numerical results of approximate solutions with the method of boundary elements (BEM) are shown.
Description of Brittle Damage in Concrete
Jan Kubik, Zbigniew Perkowski
Communications - Scientific Letters of the University of Zilina 2002, 4(3):9-12 | DOI: 10.26552/com.C.2002.3.9-12
A simple model of the brittle damage evolution in concrete is presented. The damage evolution is assumed as an isotropic one and the level of damages in material is described by the scalar parameter. The physical equations for this case are formulated.
On Shear Connection Design in Composite Beams
Jan Bujnak, Kazimierz Furtak, Jaroslav Odrobinak
Communications - Scientific Letters of the University of Zilina 2002, 4(3):13-16 | DOI: 10.26552/com.C.2002.3.13-16
The paper deals with a way of determining concrete pressure strength when calculating load carrying capacity of steel perfobond strip connectors. This type of strip connectors has been used in composite bridges only recently and no precise methods of calculating them have been worked out so far. The effect of axial forces on bearing capacity of classical stud shear connectors is also given in the paper as a result of research.
Longitudinal Shear Flow at the Support Area of Beam with an Overhanging Cantilever
Jaroslav Odrobinak, Aarne Jutila
Communications - Scientific Letters of the University of Zilina 2002, 4(3):17-20 | DOI: 10.26552/com.C.2002.3.17-20
The paper deals with longitudinal shear flow of beams near the support area. Special interest is focused on the overhanging part, which exists in all kinds of beams irrespective of material and span. A parametric study on shear stress distribution at several horizontal height levels by using FEM is presented. Special emphasis is paid to the cantilever length. Finally, conclusions for practical applications are summarized.
Design of Anchorage of CFRP Strips
Petr Stepanek, Ivana Svarickova
Communications - Scientific Letters of the University of Zilina 2002, 4(3):21-26 | DOI: 10.26552/com.C.2002.3.21-26
Anchorage of externally bonded reinforcement is the main problem for strengthening concrete structures with CFRP strips (Štěpánek & Šustalová 2000, 2001). This paper describes a form of the tests and some results implicating from different properties of anchorage elements. The test results are compared with values obtained from mathematical analysis of anchorage zones behavior and normal stress distribution along the anchorage length.
Mix Design of Stiff Concrete Mixtures Compacted by Vibration under a Surcharge Load
Jacek Sliwinski, Witold Brylicki
Communications - Scientific Letters of the University of Zilina 2002, 4(3):27-30 | DOI: 10.26552/com.C.2002.3.27-30
In the manufacture technology of products compacted by vibration under a surcharge load, such as paving blocks, it is necessary to use concrete mixtures of consistency outside the range designed for ordinary concrete. Due to the simultaneous effect of vibration and static load the concrete mixture must meet special requirements of consistency and workability. The paper presents two methods of concrete mix design which proved particularly useful for mixtures compacted by vibration under a surcharge load. The former is based on heaping up the aggregate void spaces with cement paste, the latter on coating the aggregate grains with paste.
Effect of the Fly Ash and Cement Type upon the Cement Paste Rheology
Stefania Grzeszczyk, Grzegorz Lipowski
Communications - Scientific Letters of the University of Zilina 2002, 4(3):31-34 | DOI: 10.26552/com.C.2002.3.31-34
In the paper an analysis of the the influence two types of fly ashes on rheological properties of cement pastes with cements containing different amount of C3A is presented. It was stated that a type of fly ash and content of C3A in cement have significant influence upon rhelogical behaviour of cement pastes.
Designing Workability of High Performance Concrete Using Rheometrical Workability Test
Janusz Szwabowski, Jacek Gołaszewski
Communications - Scientific Letters of the University of Zilina 2002, 4(3):35-40 | DOI: 10.26552/com.C.2002.3.35-40
In the paper the results of investigation on cement/superplasticizer compatibility in presence of air entraining agent and silica fume are presented and discussed. Investigation was carried out on standard mortars using rheometrical workability test (RWT). The research was a first step in designing HPC to be used in bridge construction. The research fully proves usefulness of RWT for estimation of compatibility of cement/SP systems and for testing of admixtures influence on rheological properties of fresh concrete.
Thermal Load Induced Changes of Hygric and Thermal Properties of Glass Fiber Reinforced Cement Composites
Robert Cerny, Michaela Totova, Jan Toman, Jaroslava Drchalova, Pavla Rovnanikova, Patrik Bayer
Communications - Scientific Letters of the University of Zilina 2002, 4(3):41-44 | DOI: 10.26552/com.C.2002.3.41-44
The effect of thermal load on the basic thermal and hygric properties of two types of glass fiber reinforced cement composites (GFRCC) is analyzed in the paper. Thermal conductivity, specific heat and moisture diffusivity are determined after high temperature exposure to 600 and 800 °C. A decrease of thermal conductivity as high as 50 % and an increase of moisture diffusivity in the range of one to two orders of magnitude are observed for all types of the studied materials after heating to 800 °C. On the other hand, specific heat and density in the same situation decrease by only about 10 %. In the analysis of the reasons for the measured differences...
Dynamic Behaviour of Railway Track - Experimental Measurements
Milan Moravcik
Communications - Scientific Letters of the University of Zilina 2002, 4(3):45-62 | DOI: 10.26552/com.C.2002.3.45-62
The objective of the paper is devoted to in situ dynamic measurements on the track structure under traffic and briefly to present some experimental approaches in order to appreciate the dynamic behaviour of the track structure. The vertical vibration of rails, sleepers and free ballast field at a distance of 1m from the track and the direct dynamic interaction force the rail / the sleeper were measured and analysed in the time and frequency domain. Received results can give many usefulindications concerning the assessing of the superstructure dynamic behaviour.
Laboratory Tests of the Interaction Zone between Reinforced Soil Components
Andrzej Surowiecki, Marek Kopinski
Communications - Scientific Letters of the University of Zilina 2002, 4(3):63-71 | DOI: 10.26552/com.C.2002.3.63-71
Laboratory investigation results related to the range of the interaction zone between a non-cohesive soil medium and vertically positioned reinforcement inserts are discussed. The investigations consisted of the measurement of the composite's side pressure; they have been carried out on large-scale models of subsoil (sand, gravel, grit) with reinforcements in the form of metal and plastic nets. It has been proved that the vertical range of the reinforcement effect zone depends upon characteristics of the soil medium and reinforcement parameters.
A Brief Overview to Theory of Heights
Robert Tenzer
Communications - Scientific Letters of the University of Zilina 2002, 4(3):72-79 | DOI: 10.26552/com.C.2002.3.72-79
In various parts of the world many kinds of height systems have been formulated and practically used in the past. Nowadays, orthometric heights and normal heights are widely used. The orthometric heights are the natural heights above sea level, that is, above the geoid. The definition of the orthometric heights required the knowledge of the topographical masses density distribution between the Earth's surface and the geoid, at least theoretically. For this reason Molodensky in 1945 formed a theory of normal heights based on the principle that the heights can be evaluated without any hypothesis about the density distribution of topographical masses....
Modelling of the Noise Processes
Rastislav Lukac, Viktor Fischer, Pavol Galajda
Communications - Scientific Letters of the University of Zilina 2002, 4(3):80-88 | DOI: 10.26552/com.C.2002.3.80-88
In this paper, the modelling of noise processes and their application to image processing are described. Thus, the noise effect on useful image information is presented and analysed according to mathematical formulas, the reason of its origin, introduced visual changes and the possibility of their reduction. In order to provide an unbiased view on the noise effect, noise models are supported by a number of object-lesson figures.