rss_2.0Slovak Journal of Civil Engineering FeedSciendo RSS Feed for Slovak Journal of Civil Engineering Journal of Civil Engineering 's Cover Domaša Reservoir in the Spectrum of Climate Change<abstract> <title style='display:none'>Abstract</title> <p>The importance of water reservoirs in the uneven distribution of discharges over time and space does not need to be explicitly justified. There is a more than 6,000-year history of convincing evidence. In Slovakia, the construction of reservoirs can be dated to two periods. The first period was the 18th century, when the construction of water reservoirs was stimulated by the need for water for the mining industry in the vicinity of the town of Bánska Štiavnica. The second period falls into the second half of the 20th century. The construction of reservoirs was initiated by the post-war period, including the need to increase society’s standard of living, the electrification of the region, the development of industry and agriculture, flood protection, etc. Reservoirs with multi-annual regulations have an essential position in the types of water reservoirs. While small water reservoirs and annual or seasonal regulation can regulate flows in a short period, reservoirs with multi-annual regulation can regulate flows over several years. This benefit is evident, especially during periods of extreme hydrological phenomena and short-term aquatic and long-term dry, so-called low water periods. We have illustrated our knowledge of and experience gained from their impact on the flows downstream of the Veľká Domaša dam. We analyzed two time periods, i.e., before and after the year 2000. The influence of extreme hydrological phenomena on the runoff conditions downstream of the dam is presented by statistical processing of the available flow series</p> </abstract>ARTICLE2021-07-12T00:00:00.000+00:00The Reinforcement of Sand by Fibres with a Non-Uniform Shape<abstract> <title style='display:none'>Abstract</title> <p>The reinforcement of soil is used to improve its strength and stiffness. The standard method of soil reinforcement is an application of geosynthetics. Soil reinforcement by distributed discrete fibres represents an alternative to those techniques. Currently used fibres have a straight shape, uniform cross-section, and smooth surface, which is not optimal in terms of the fibre-soil interaction. In this study, fibres with a variable shape were utilized. The fibres were fabricated using a fused deposition modelling technology. Firstly, a brief theoretical background is presented. Then, the proposed shapes of the fibres and their manufacturing process are described. The mechanical properties of the soil-fibre composite were investigated through consolidated drained triaxial tests. Well-graded coarse sand and poorly-graded fine sand were used. A higher peak shear strength was observed in the case of fibres with a variable shape. The effect of the variable shape of the fibres on the peak shear strength was higher in the case of the coarse sand.</p> </abstract>ARTICLE2021-07-12T00:00:00.000+00:00Aerodynamic Study of the Wind Flow in the Area of the R2 Expressway in Slovakia<abstract> <title style='display:none'>Abstract</title> <p>Our calculation of wind effects was based on the specific wind situation of the planned R2 expressway. Given the topography and the prevailing wind directions, it was necessary to analyse the speeds for winds that could cause vehicles with trailers to be pushed off the roadway, as has been observed in recent years. Using a CFD simulation in the ANSYS FLUENT program, we analysed the entire section of the planned R2 expressway in order to evaluate the wind speeds at the level of the centre of gravity of truck trailers. Statistical turbulence models based on a time-averaging method, i.e., the RANS-Reynolds Averaged Navier-Stokes equations, of turbulent flow quantities and the time-averaging procedure of balance equations are suitable for solving the engineering tasks. In numerical simulations, the Realizable k - ε model was used in which the calculation of the turbulent dynamic viscosity in the equation for Boussinesque’s hypothesis was solved using two transport equations. Plotting and comparing the wind speeds for significant wind directions allowed us to design protection in the dangerous areas using protective walls.</p> </abstract>ARTICLE2021-07-12T00:00:00.000+00:00Determination of Subgrade Reaction Coefficients and Spring Stiffnesses for a Combined Pile Raft Foundation (CPRF) by Means of a Cluster Analysis<abstract> <title style='display:none'>Abstract</title> <p>An analysis of combined piled raft foundations could be performed by means of a special geotechnical finite element software that utilizes 3D modeling and advanced constitutive models for the soil. However, a foundation is generally included in the structural models in a structural design program. The least advanced part of finite element software that has been developed for structural FEM modeling are the tools used for modeling behaviour. A method is required with which the input parameters of the structural design software that are used for modeling the soil structure interaction as well could be determined so that the results calculated by means of a geo-technical software that approximates realistic soil behaviour the best can be reproduced by structural design software as well. The procedure outlined in this paper by means of a cluster analysis provides a tool for a substantial and innovative improvement in subsoil modeling, to which not enough attention is generally paid in the structural FEM software, thereby resulting in a reduced amount of work associated with the task of inputting data.</p> </abstract>ARTICLE2021-07-12T00:00:00.000+00:00Non-Hydrostatic Transitional Open-Channel Flows from a Supercritical to a Subcritical State<abstract> <title style='display:none'>Abstract</title> <p>In this study, a depth-averaged numerical model was employed to investigate the two-dimensional flow features of transitional open-channel flows from a supercritical to a subcritical state. Compared to a shallow-water model, the proposed model incorporates supplementary terms to account for the effects of non-uniform velocity and non-hydrostatic pressure distributions. The model equation was solved numerically by means of the Adams–Bashforth–Moulton scheme. A wide variety of transitional open-channel flow problems such as hydraulic jumps was considered for assessing the suitability of the numerical model. The results of the model for the free-surface profile, pressure distribution, and characteristics of the first wave of an undular jump were compared with the experimental data, and the agreement was found to be satisfactory. Despite the effects of the three-dimensional characteristics of the flow and the bulking of the flow caused by air entrainment, the model performed reasonably well with respect to the simulations of the mean flow characteristics of the curvilinear turbulent flow problems. Furthermore, the results of this investigation confirmed that the model is more suitable for analyzing near-critical turbulent flow problems without cross-channel shock waves.</p> </abstract>ARTICLE2021-07-12T00:00:00.000+00:00Comparative analysis of Activated Corn Cob and Bentonite Clay for the Removal of Lead and Nickel from Raw Water<abstract> <title style='display:none'>Abstract</title> <p>The extensive use of commercial activated carbon as an adsorbent for the purification of industrial effluent is not economical for small and medium-sized enterprises due to its high operational cost. This study was carried out to compare the adsorptive capacity of bentonite clay and activated corn cob (“BC” and “ACC”) for the removal of lead (II) and nickel (II) ions from an aqueous solution. The results obtained from the characterization of the BC and ACC are pH: 7.43 and 6.74; moisture content: 36.45kg/kg and 12.10kg/kg, and bulk density: 1.243g/ml and 1.162g/ml, respectively. Normality tests using the coefficient of skewness indicated that the set of data was not normally distributed. An analysis of variance (ANOVA) test conducted using Friedman’s 2-way ANOVA test indicated p values of 0.0253 against an alpha value of 0.05, which indicates significance. The Friedman results indicated significance with respect to the varied dosages, initial concentrations, and contact time. The effect of the adsorbent was not significant. The adsorption isotherms were analysed using the Langmuir, Freundlich, and Temkin isotherms. Most research studies have shown that adsorption experiments performed using most low-cost materials tend to follow the Freundlich adsorption isotherm, but the results of this experimental study proved that activated corn cob and bentonite clay performed better with the Temkin adsorption isotherm with 0.879 ≤ R<sup>2</sup> ≤ 0.917 for the bentonite clay and 0.9572 ≤ R<sup>2</sup> ≤ 0.99 for the activated corn cob respectively. The study revealed that these materials are good adsorbents that can be used for the removal of lead (II) and nickel (II) ions from an aqueous solution.</p> </abstract>ARTICLE2021-07-12T00:00:00.000+00:00Effect of Modifying Aggregates by Rap and the Simultaneous use of Adhesives for the Stabilization of a Sandy Pavement Subgrade<abstract> <title style='display:none'>Abstract</title> <p>The improvement, reconstruction and repair of roads in recent years have increased the content of recycled asphalt in pavements. Using these materials in road construction projects because they reduce the costs, will also be of great help in improving environmental issues. In the present study, dune sand, which can be found in most desert area soil but does not have proper strength and loading capacity for a subgrade, was used. In order to increase the strength parameters of dune sand, various contents of cement and recycled asphalt were examined in California Bearing Ratio (CBR) and compressive strength tests. The results showed that the addition of cement and recycled asphalt can increase compressive strength and bearing capacity and reduce rupture deformations. In a stabilized sample with 27.5% recycled asphalt, increasing the cement from 7.5 to 12.5% increased the compressive strength by 1.045 times, which is the highest amount of change in the samples studied. The maximum CBR and minimum rupture deformations are related to 35% of the recycled asphalt and 12.5% of the cement. The predicted functions of the compressive strength, deformation and CBR depend on two variables of the cement content; the recycled asphalt was then calculated using the response surface method</p> </abstract>ARTICLE2021-07-12T00:00:00.000+00:00Evaluation of the Cohesive Properties of SBS-Modified Binders at Low Temperatures<abstract> <title style='display:none'>Abstract</title> <p>The durability, fatigue resistance, and low-temperature behavior of asphalt layers are greatly affected by the properties of bitumen. Therefore, the composition of bitumen is frequently modified to improve the performance of asphalt mixtures. Sty-rene-butadiene-styrene (SBS) has been the most often used additive recently. Researchers are trying to improve the cohesive and adhesive properties of binders by such polymer-based additives. In this study, 160/220 penetration grade bitumen and Kraton D 1101 SBS were used. The present study contains a new evaluation for determining the cohesive behavior of SBS-modified binders at -1°C, -3°C, and -5°C. The results of this evaluation were compared to conventional and rheological test results. Penetration, softening point, viscosity, dynamic shear rheometer, and bending beam rheometer tests were therefore conducted. Finally, the results of a low-temperature tensile test were found to be consistent with the results of the other tests; hence, they also confirm the cohesive behavior of SBS-modified binders at low temperatures.</p> </abstract>ARTICLE2021-04-13T00:00:00.000+00:00Sound Absorption Properties of Materials Based on Recycled Plastic Granule Mixtures<abstract> <title style='display:none'>Abstract</title> <p>This article reports on impedance tube measurements of the sound absorption coefficient α (-) of selected recycled foam plastics, i.e., ethylene-vinyl acetate (EVA), polyvinyl chloride (PVC), polystyrene (PS), and polypropylene (PP), in different mixtures with a binding adhesive. The effect of the thickness of the sample on the sound absorption spectrum as well as the variability in absorption across the different samples of the same composition and thickness are discussed. For the EVA/ PP and PS/PP mixtures, the spectrum is characterized by two peaks that shift as the thickness is changing. These mixtures were also found to be the most absorbent across the whole audible frequency range.</p> </abstract>ARTICLE2021-04-13T00:00:00.000+00:00Thermaly Active Interior Panels with an Integrated Active Area<abstract> <title style='display:none'>Abstract</title> <p>Panels with an integrated active area can be used for interior applications for walls, ceilings and floor heating, and alternatively as a wet or dry type of construction. At present, most panels with an integrated active area are made of gypsum boards with milled channels and embedded pipes. Some manufacturers already supply these panels with thermal insulation (Radwan et al., 2021; Zhang et al., 2020). Certain limitations, mainly regarding the diameter and material of the pipes, apply to the panels with channels milled in the gypsum board and embedded pipes. These limitations are closely related to the high cost of such panels and to the limited heat/cooling output. The disadvantages of these panels are eliminated by the construction of a thermal insulation panel with active thermal protection for application with an active heat transfer control system (indoor thermally active panel (ITAP)) in accordance with European Patent No. EP 2 572 057 B1 (Kalús, 2011).</p> </abstract>ARTICLE2021-04-13T00:00:00.000+00:00Effects of Interference on Local Peak Pressures Between Two Buildings with an Elliptical Cross-Section<abstract> <title style='display:none'>Abstract</title> <p>The interference effects on the distribution of external wind pressure coefficient between two high-rise buildings with an elliptical cross section were studied experimentally at the Boundary Layer Wind Tunnel (BLWT) at the Faculty of Civil Engineering STU in Bratislava, Slovakia. Various arrangements of models, which were derived from the breadth ratio, were investigated. The peak value of the external wind pressure coefficient for a stand-alone model was measured and compared with the peak value in the case of interference. The measurements showed that the wind loads on buildings in a close vicinity are considerably different from those on a stand-alone building. The interference effects significantly affect negative pressure zones. The optimal and critical arrangements of buildings were evaluated. The elimination of peak negative external wind pressure coefficients can be reduced by half. On the other hand, the interference effects had a strong impact on increasing the peak value of the negative external wind pressure coefficient, which can be more than roughly double compared to an isolated building.</p> </abstract>ARTICLE2021-04-13T00:00:00.000+00:00Analysis of a Topsoil Moisture Regime Through an Effective Precipitation Index for the Locality of Nitra, Slovakia<abstract> <title style='display:none'>Abstract</title> <p>The aim of this work was to analyze and statistically confirm the relationship between the computed daily values of the Effective Precipitation Index (EP365) and the measured moisture content of the topsoil of a research site near Nitra, Slovakia. The statistical analysis (coefficients of determination) confirmed the strong correlation. Subsequently each day’s mean of EP365 (MEP) was used to quantify the long-term deficit or surplus of the soil water supply in the individual years. The daily values of the EP365 index provide a more detailed view of the development of the topsoil’s moisture regime. According to the deviation of EP (DEP) from the 14-year MEP, the most extreme dry periods prevailed during the years 2015, 2017 and 2018. Therefore, the 2012–2018period was evaluated as dry, and the topsoil moisture regime described through the MEP index was compared with the course of the MEP index from the normal (slightly humid) period of the years 2005 – 2011.</p> </abstract>ARTICLE2021-04-13T00:00:00.000+00:00Simulation Modelling of Aerial Works and Its Role in the Preparation of Construction<abstract> <title style='display:none'>Abstract</title> <p>The construction process is characterized by a diverse technological composition and the use of a wide range of construction machinery and mechanization. The amount of machinery increases with the complexity of the construction, which increases the demands concerning the preparation and overall organisation of the construction. The preparation of construction processes carried out by helicopters (aerial work) must respect the effect of randomly changing construction conditions as well as the specific working conditions of helicopters. The complexity of such a system can be modelled using simulation models. In the work presented, we designed and practically tested a simulation model of aerial work in the MATLAB software environment. An essential part of the simulation model is an algorithm designed on the basis of commercial numerical weather prediction models. We consider the outputs of the simulation to be reliable, because they are very close to the actual results achieved in the case of the implementation of construction of this type. The concept of the simulation model enables its wider use not only in the construction sector, but also in other branches of industry.</p> </abstract>ARTICLE2021-04-13T00:00:00.000+00:00Effect of the Temperature on the Modal Properties of a Steel Railroad Bridge<abstract> <title style='display:none'>Abstract</title> <p>The article is devoted to a study of the impact of various environmental conditions on modal parameters, such as natural frequencies and damping ratios. The modal analysis has been performed using the Stochastic Subspace Identification (SSI) method of measuring data every month on the same steel bridge structures located on an important railroad route from Prague (the Czech Republic) to Košice (Slovakia). The structure is approximately 60 m long, and the bearing structure is formed by two arch trusses. The bridge was exposed to ambient vibrations as well as to vibrations caused by a train passage. Accelerations and temperatures (the temperature of the air and the structure) were logged during the measurements. Natural frequencies were obtained from these acceleration data using the SSI method and processed into graphs of the dependencies between the natural frequencies and temperatures. Some statistical procedures were also applied.</p> </abstract>ARTICLE2021-04-13T00:00:00.000+00:00Investing in European market real property through reits<abstract xml:lang="en"><title style='display:none'>Investing in European market real property through reits</title><p>For institutional and private investors, investing in real estate represents an attractive form of the consignment of their money. Real estate provides a regular source of income in the form of the rent from or interest on the credit provided. At the same time, real estate is a good investment instrument, because it provides diversified contributions and security against inflation for investors. In their efforts to diversify risk, investors are expressing growing interest in investing in the whole European Union. The success of Real Estate Investment Trusts (REITs) in the U.S. also opened the door for investing in this market for small investors, which is the reason for the development of this type of investment company in the European arena. One problem concerning the development of European real estate investment funds is the unsolved issue of the harmonization of the legislation and regulatory safety measures, which would enable the creation of a common market for new investment products in Europe.</p></abstract>ARTICLE2011-06-07T00:00:00.000+00:00The global economy and its influence on the Slovak construction sector<abstract xml:lang="en"><title style='display:none'>The global economy and its influence on the Slovak construction sector</title><p>For the construction industry, globalization is a trend that means two things: many opportunities and many threats. In the conditions of globalization many management approaches, such as organization structure, strategy forming, planning, motivation and control procedures, communication channels, risk management, etc., must transform. The aim of the paper is to analyze the influence of globalization on the construction industry in Slovakia and identify the impact of globalization on construction companies in this area.</p></abstract>ARTICLE2011-06-07T00:00:00.000+00:00Deterministic and probabilistic analysis of damping device resistance under impact loads from nuclear fuel container drop<abstract xml:lang="en"><title style='display:none'>Deterministic and probabilistic analysis of damping device resistance under impact loads from nuclear fuel container drop</title><p>This paper presents a deterministic and probabilistic solution of damping devices for the protection of the reinforced concrete structure of a nuclear power plant (NPP) from impact loads from a container of nuclear fuel of the type TK C30 drop. The finite element idealization of the building structure is used in space. The interaction soil-structure, as well as the fluid-structure of the deactivated basin is considered in space. A steel pipe damper system is proposed for the dissipation of the kinetic energy of the container in free fall. The Newmark integration method is used for the solution of the dynamic equations. The sensitivity and probabilistic analysis of the damping devices was realized using the AntHILL and ANSYS software.</p></abstract>ARTICLE2011-06-07T00:00:00.000+00:00Applications of mathematical methods in the supervision of the technical safety of water constructions<abstract xml:lang="en"><title style='display:none'>Applications of mathematical methods in the supervision of the technical safety of water constructions</title><p>In this paper, we present the use of time series (stochastic models) in order to predict water seepage in the wells of water constructions. The aim of this paper is to assess the agreement between the predicted and measured levels of the water seepage in the wells of the Liptovska Mara water construction. We assume that the predicted values will match the values that were measured. The ability to predict the level of the water in observation wells and the total filtration stability of water constructions by using real measures in a time series is a desirable step in ensuring adequate safety with the possibility of remedying potential defects at an early stage.</p></abstract>ARTICLE2011-06-07T00:00:00.000+00:00Method for the Accelerated Testing of the Durability of a Construction Binder using the Arrhenius Approach<p>The single most reliable indicator of a material’s durability is its performance in long-term tests, which cannot always be carried out due to a limited time budget. The second option is to perform some kind of accelerated durability tests. The aim of the work described in this article was to develop a method for the accelerated durability testing of binders. It was decided that the Arrhenius equation approach and the theory of chemical reaction kinetics would be applied in this case. The degradation process has been simplified to a single quantifiable parameter, which became compressive strength. A model hydraulic binder based on fluidised bed combustion ash (FBC ash) was chosen as the test subject for the development of the method. The model binder and its hydration products were tested by high-temperature X-ray diffraction analysis. The main hydration product of this binder was ettringite. Due to the thermodynamic instability of this mineral, it was possible to verify the proposed method via long term testing. In order to accelerate the chemical reactions in the binder, four combinations of two temperatures (65 and 85°C) and two different relative humidities (14 and 100%) were used. The upper temperature limit was chosen because of the results of the high-temperature x-ray testing of the ettringite’s decomposition. The calculation formulae for the accelerated durability tests were derived on the basis of data regarding the decrease in compressive strength under the conditions imposed by the four above-mentioned combinations. The mineralogical composition of the binder after degradation was also described. The final degradation product was gypsum under dry conditions and monosulphate under wet conditions. The validity of the method and formula was subsequently verified by means of long-term testing. A very good correspondence between the calculated and real values was achieved. The deviation of these values did not exceed 5 %. The designed and verified method does not also consider the influence of other effects, for instance, chemical corrosion or corrosion caused by frost-thaw cycles. However, this method could be a supplementary tool applicable to the study of degradation processes and the estimation of a binder´s durability as well.</p>ARTICLE2016-04-18T00:00:00.000+00:00Morphometrical Analysis and Peak Runoff Estimation for the Sub-Lower Niger River Basin, Nigeria<p>This study utilized Spatial Information Technology (SIT) such as Remote Sensing (RS), a Geographical Information System (GIS), the Global Positioning System (GPS) and a high-resolution Digital Elevation Model (DEM) for a morphometrical analysis of five sub-basins within the Lower Niger River Basin, Nigeria. Morpho-metrical parameters, such as the total relief, relative relief, relief ratio, ruggedness number, texture ratio, elongation ratio, circularity ratio, form factor ratio, drainage density, stream frequency, sinuosity factor and bifurcation ratio, have been computed and analyzed. The study revealed that the contribution of the morphometric parameters to flooding suggest catchment No. 1 has the least concentration time and the highest runoff depth. Catchment No. 4 has the highest circularity ratio (0.35) as the most hazardous site where floods could reach a great volume over a small area.</p>ARTICLE2016-04-18T00:00:00.000+00:00en-us-1