rss_2.0Slovak Journal of Civil Engineering FeedSciendo RSS Feed for Slovak Journal of Civil Engineering Journal of Civil Engineering Feed Angle of the Shear Resistance of Danube Gravel Derived from the Dynamic Penetration Test<abstract> <title style='display:none'>Abstract</title> <p>The dynamic penetration test was used to investigate the angle of shear strength of Danube gravel. The correlations for its determination are available in the standards and literature. From the data set of the results, the characteristic value of the angles of shear strength was derived according to the recommended statistical procedure from the second generation of Eurocode 7. The characteristic values of the angle of shear strength were evaluated for well-graded gravels, poor-graded gravels, and gravels with fine-grained particles of the Danube. The correlations, which were based on field tests and considered the genesis of the soil, were compared with laboratory test results and a table of the values from the Slovak standard, which are used for purposes of comparison.</p> <p>In our research we compared the characteristic field values of the angle of shear strength obtained in the laboratory to observe the effect of their genesis on the appropriateness of the correlations used. We conclude with recommendations for the regional correlations and suggest values of the angle of shear strength for the classes of gravels tested.</p> </abstract>ARTICLEtrue of Cracks in Concrete with the Microbial-Induced Calcite Precipitation (MICP) Method<abstract> <title style='display:none'>Abstract</title> <p>In this study, the microbiologically-induced calcium carbonate precipitation (MICP) method was employed to examine its potential for repairing cracks in concrete. In addition, specific gravity and porosity values were measured to examine the effect of calcite formations on concrete surfaces and microstructures. Bacteria-supplemented concrete repaired cracks up to 0.4 mm wide by filling them with CaCO3. Furthermore, this study not only examined the healing of the width but also the length of cracks. However, as the width of the treated cracks decreased, their length increased. This indicated that the MICP treatment is more effective in a limited crack range. Specific gravity values increased, and porosity values decreased in concrete supplemented with calcifying bacteria. SEM analyses showed that calcite is a bacterial product that forms a very tight bond with a cement gel and that calcite fills visible cracks and voids and creates more of a void-free and undamaged concrete structure.</p> </abstract>ARTICLEtrue of Recovered Fibers on the Behavior of Concrete in Tension<abstract> <title style='display:none'>Abstract</title> <p>This study evaluates the performance of concrete under the effect of the addition of non-straight fibers recovered during the machining of steel parts and then studies the effect of the addition of corrugated fibers (chips) on their behavior in direct traction of the fiber concrete. In order to characterize the mechanical behavior and tearing of these fibers, three lengths of fibers were used (4 cm, 5 cm, and 6 cm); for each length we varied the percentage by volume (0.3%, 0.5%, 0.8%, 1%, and 1.2%). To make a comparative study, a second series of tests was carried out with control concrete (BT) without any fibers of the same composition. The results of the tests carried out indicate that the resistance and stiffness are significantly improved and that the fibers imparted significant ductility to the material compared to the control concrete. It was also observed that the percentage of fibers significantly influences the appearance of cracks. Moreover, with an increase in the percentage of fibers from 0.3% to 0.8%, the resistance increases, but beyond a content of 0.8%, the mechanical characteristics decrease.</p> </abstract>ARTICLEtrue Contribution to Study the Physico-Mechanical and Thermal Properties of Lightweight Cellular Concrete Prepared With Different Types of Sand and Waste Marble Powder<abstract> <title style='display:none'>Abstract</title> <p>Algeria is currently undergoing an evolution in civil engineering, which has resulted in a higher use of aggregates, especially sand. This study contributes to the development of locally produced materials. Its goal is to explore how the type of sand and waste marble powder (WMP), which can be used as a partial replacement of cement and aluminum powder (Al) with different percentages as an expansive agent, can affect physico-mechanical properties such as the bulk density and mechanical strength at 28 and 90 days, as well as the thermal conductivity of lightweight cellular concrete. Non-autoclaved cellular concretes (CC) were investigated based on three types of sand, i.e., sea sand (SS), river sand (RS), and waste marble sand (WMS); a hydraulic binder (a mix of cement and waste marble powder), and aluminum powder. The experimental results indicate that the nature and particle size distribution of the sand used had an impact on the properties of the CCs. Furthermore, it can be seen that the increased aluminum contents decrease the density, mechanical strength, and thermal characteristics of the CCs. Using 10-15% WMP as a cement substitute improves the mechanical strength, offers better thermal conductivity values, and contributes to sustainable development by developing a new class of environmentally friendly cellular concrete.</p> </abstract>ARTICLEtrue Use of Vertical Gardens as a Network of Urban Navigation Elements with a Positive Impact on Biodiversity and Microclimate in a Dense Urban Environment<abstract> <title style='display:none'>Abstract</title> <p>Horizontal green areas are becoming valuable, yet extruded spots, and their constant elimination at the expense of commercial and housing developments is disrupting green infrastructure. Interlocked existing urban structures seldom allow for the creation of parks and larger green open spaces, which could provide a habitat for a wide range of insects, birds, and other small animals. The lack of green spaces causes urban heat islands (UHI) over the cities. Vertical gardens are alternative solutions for urban areas, where it is not possible to increase biodiversity by creating new horizontal green areas. They effectively utilise surfaces that would otherwise be unused and transform them into effective green infrastructure elements.</p> <p>Using the example of the historical city district of Bratislava, i.e., Old Town (Staré Mesto) in Slovakia, we present an alternative approach for resolving the lack of green areas. A case study was conducted to create a map of all the potentially suitable areas for the construction of vertical gardens. We divided these spots into three groups, i.e., walls, columns, and free-standing structures and proposed construction methods for each type. Regarding the placement of potentially suitable areas along the roads connecting important transport hubs with the city centre, we created an original proposal for a district-wide network of vertical gardens as orientation elements for tourists and residents with significant aesthetic merit as well as ecological and hygienic values.</p> </abstract>ARTICLEtrue of the Indoor Climate in a Small, Newly-Built Auditorium<abstract> <title style='display:none'>Abstract</title> <p>The article focuses on an analysis of the indoor climate in a small, newly-built auditorium. Providing optimal indoor climate parameters in the interiors of a university is extremely important for students. Meeting these parameters is essential not only from a physiological point of view, but also to achieve desirable student performances. The parameters of CO2 concentration are also influenced by the air distribution system in a small auditorium. The correct positions of the supply and extract air is very important. The first experimental measurements of CO2 concentration were carried out in a small auditorium in an old building. The natural ventilation of the small auditorium was evaluated. The second experimental measurements of the CO2 concentration were made in a small auditorium in a newly-built building. The ventilation system and the modern air distribution system of the small, newly-built auditorium were evaluated based on the CO2 concentration and the PMV index. A Testo 480 was used for the measurements. The conclusion of this paper contains the recommendations for the design of a newly-built ventilation system in a small auditorium.</p> </abstract>ARTICLEtrue of an Embankment on Stone Column-Reinforced Soft Soil<abstract> <title style='display:none'>Abstract</title> <p>Reinforcing soft soils with good drainage and load-bearing material is a common practice in the construction of embankments. Stone columns are among the granular materials that accelerate consolidation settlements due to their high drainage capacities. This study aims to investigate the behavior of an embankment on stone column-reinforced soft soil. The embankment was analyzed using the Plaxis 2D Finite Element Method. The columns were converted into equivalent walls using the plane strain conversion method. This method was validated with field measurement results from previous studies and showed good agreement. According to the research findings, stone columns significantly reduced deformations and improved consolidation. For instance, the ultimate settlement was decreased from 54.3 mm to 33.1 mm for 10% and 20% area replacement ratios, respectively. As the safety analysis verified, basal geosynthetics contributed substantially to the embankment’s stability. Furthermore, the safety factor values increased for all stages of the construction, and the global safety factor increased at the end of the construction. Stone columns and basal geogrid-reinforced soft soil can reduce settlement and increase the stability of an embankment.</p> </abstract>ARTICLEtrue of a Conceptual Snow Sub-Model: Application in Meteorological Stations, Slovakia<abstract> <title style='display:none'>Abstract</title> <p>A semi-distributed rainfall-runoff Approximate Redistributive Balance (ARB) model is currently in development as a tool for the assessment and analysis of the water management balance at the level of micro-basins on the territory of Slovakia. For the winter season, it is necessary to supplement the model with a sub-model for calculating the snow water equivalent (SWE) with a comparatively low amount of the input data necessary. Since SWE models generally operate in a daily time step, a new sub-model was developed and tested in monthly and weekly time steps in 30 meteorological stations in the north of Slovakia. When compared in a weekly time step with the snow sub-model of the HBV rainfall-runoff model and when the impact of switching from a monthly to weekly time step on the quality of the runoff simulation was evaluated, the results showed that the snow sub-model does react to sudden snowmelt better when compared to the modified version of the HBV snow sub-model used. Using a weekly time step for the snow sub-model in a monthly ARB model runoff simulation showed an increase of accuracy (NSE change from 0.89 to 0.92) in one case, while maintaining the same level of accuracy in the second one.</p> </abstract>ARTICLEtrue of Embankment of an Ore Tailings Pond and an Analysis of its Stability<abstract> <title style='display:none'>Abstract</title> <p>The article presents a method for the intensification of a tailings pond. A tailings pond serves for the hydraulic storage of silt-sand waste arising during a flotation treatment and the processing of polymetallic ores. The intensification of the tailings pond consisted of raising its dam system to increase its accumulation space. The total proposed height of the tailings pond dam system after its elevation will be 60 m. The structural and shape arrangement of the dam in the dam system of the tailings pond was the result of a stability analysis of the state of the tailings pond before and after the dam system was raised. The article presents the results of experimental verifications of the geomaterial properties that form quasi-homogeneous units of the tailings pond (subsoil, dam system, and sediment) that serve as the inputs for stability analyses. New limiting and critical water levels are modelled based on the stability analysis for the intensified dam system of the tailings pond, taking into account the standard requirements for its overall stability.</p> </abstract>ARTICLEtrue of the Probability of Exceeding the Limiting Deformations of a Building Foundation<abstract> <title style='display:none'>Abstract</title> <p>The level of ground settlement under the effect of certain factors is one of the markers indicating the adequacy of adopted design solutions. By comprehending settlement values, it is possible to infer the degree of risk associated with a project and, if necessary, introduce changes to the design. The concept of reliability management here manifests itself in the timely adjustment of the decisions made, while it is necessary to use the procedure of the quantitative assessment of the probability of the occurrence of a particular limit state. A qualitative assessment indicates only the limits of an area, which approximately characterizes the effects of changes in the geotechnical situation. In this article, a method for determining the probability of exceeding the limit deformation of a building-base massif using the Monte Carlo statistical method is developed, and an algorithm and computer program implementing the proposed calculation method are created.</p> </abstract>ARTICLEtrue and Modification of Chip-Cement Wooden Composites Based on Recycled Plastics<abstract> <title style='display:none'>Abstract</title> <p>The production of plastics and the associated increasing amount of plastic waste is currently a serious environmental problem that has a negative impact on the environment. It is necessary to develop new methods of recycling and also solutions for the further use of already recycled plastics. Thus far, a lot of research has been devoted to this issue, which focuses on the effective recycling and reuse of recycled plastic in the construction sector. One of the possibilities is the application of a filler substitute in concrete, which is an economically and ecologically advantageous solution that ensures optimal thermal insulation and acoustic properties. The aim of this study was to analyze the potential replacement of conventional aggregates in lightweight concrete, with a filler made of recycled plastic with a lower bulk density. In the research, wood chips were used in combination with recycled waste fillers including polystyrene (SE), polyethene (SP), and polyurethane foam (SU) in ratios of 1:3, 1:1, and 3:1 as an alternative to conventional filler. Concrete composites from these materials were prepared and characterized by their bulk density, thermal conductivity and compressive strength parameters.</p> </abstract>ARTICLEtrue of the Constructive Nonlinearity of Ribbed Reinforced Concrete Slabs of Self-Stressed Covering Panels<abstract> <title style='display:none'>Abstract</title> <p>Precast reinforced concrete constructions meet the requirements of industrialization, high manufacturability, and cost-effectiveness at a reasonably high level. The ribs in constructions perform load-bearing functions, and the slab part performs enclosing functions. Often before the installation of such structures at a construction site, they are mounted from assembly elements. The overall dimensions of the elements are limited by transportation requirements. During such an aggregated mounting, the assembly units work according to a calculation scheme that differs from an operational scheme. The structural nonlinearity of ribbed reinforced concrete slabs during transportation, mounting, and installation, and the operation of a combined spatial covering panel were investigated in this paper. The effects were identified, and a rational design of nodes connecting the individual prefabricated units into a spatial structure was developed. With the help of these nodes, it is possible to create unloading support moments, which will reduce the internal forces in the design cross-sections. The effects of changes in the width of the reinforced concrete slab shelves on the internal forces of the load-bearing ribs of a wall and a roof panel were investigated.</p> </abstract>ARTICLEtrue Study on Concrete by Adding Polyester Fibres<abstract> <title style='display:none'>Abstract</title> <p>There are increased innovations in the field of concrete because there are endless opportunities for innovative materials, techniques, applications, and design. Today’s construction industry is looking for cost-effective materials to improve the strength of concrete structures. As a result, an attempt has been made in the current research to investigate the impact of adding polyester fibres (Recron 3s) to concrete. Fibres improve concrete's tensile and flexural strength, fatigue properties, durability, shrinkage properties, impact and erosion resistance, and serviceability. Polyester fibres (Recron 3s) are micro fibres; they contribute to enhancing the resistance of concrete to shrinkage and cracking and also help to improve mechanical properties such as the flexural / split tensile and transverse strength of concrete along with improvements in abrasion and impact strength. An experimental study was done using a M30 mix design. Polyester fibres (Recron 3s) were used in the concrete with varying dosage rates of 0.50 kgs / cu.m – 2.00 kgs / cu.m. This study describes the enhancement in the strength of the M30 grade mix concrete by the addition of polyester fibres (Recron 3s) in the proportions of 0.5, 1, 1.5, 2.0kg/cu.m, and M30 concrete with varying dosages of the polyester fibres (Recron 3s) were mixed and cast.</p> </abstract>ARTICLEtrue Study of the Sedimentation and Storage Capacity Depletion of a Reservoir<abstract> <title style='display:none'>Abstract</title> <p>Theoretical and empirical equations have previously been proposed to compute the sediment trap efficiency of a reservoir. The empirical equations were developed by analyzing a limited amount of field data for reservoirs in selected areas; thus, their suitability is restricted to reservoirs in regions with similar hydrological characteristics. In this study, a sediment trap-efficiency equation, which accounts for the dynamic behavior of sedimentation and the hydraulic conditions of a reservoir, was deduced from the principle of mass conservation. Using this equation, the approximate analytical expression for the storage capacity of the reservoir was obtained. Both equations were applied to investigate real-life problems involving the impacts of reservoir sedimentation, and their predicted solutions were compared with the field data and the results of the theoretical and empirical equations. The results of this investigation reveal that the proposed equations are capable of simulating the sediment trapping and storage capacity depletion characteristics of large reservoirs, which are a measure of the adverse effect of sedimentation on the performance of hydraulic structures. These equations can potentially be incorporated into a large-scale watershed model for estimating a sediment budget.</p> </abstract>ARTICLEtrue of Coarse Aggregate Rap Content on the Mechanical and Shear Performance of HMA by the UPT Method<abstract> <title style='display:none'>Abstract</title> <p>In recent years, the use of materials derived from recycled asphalt has attracted the attention of airfield and highway construction researchers. Since the making of these products is economically cost-effective, one idea about how to use them is to use coarse-grained crumbs from recycled Asphalt Pavement (RAP), which are agglomerates that can be found in coarse RAP, as a replacement for virgin asphalt.The goal of the current study is to investigate the performance of hot mix asphalt created with various percents of RAP. The punching shear strength of cylindrical specimens versus the penetration of steel rods with fixed and determined diameters into an asphalt specimen is one of the tests used to study the shear strength of asphalt. Other typical tests include a test of the structural strength and resilient modulus with two rectangular and sinusoidal loading shapes, respectively, as well as the specimen's strength against different temperatures of asphalt mixtures containing 10, 20, and 30% coarse-grained RAP. The results show that the resilient strength of the samples with a maximum 30% coarse-grained RAP is within reasonable limits. Furthermore, the semi-sinusoidal loading has a higher resilience modulus than rectangular loading. It is also observed during uniaxial penetration testing (UPT) that increasing the RAP increases the penetration of the steel rod, thereby implying that the shear strength of the asphalt has decreased.</p> </abstract>ARTICLEtrue of a Measurement Turbulence Model of the Wind Pressure on the Ruin of a Fortified Tower<abstract> <title style='display:none'>Abstract</title> <p>An analysis of the external pressure coefficient on the surface of a ruin in different flow directions is presented. The ruin has almost cube-like proportions with an open roof plane and a destroyed corner. Flow simulations were performed using 3D Time Steady RANS and compared with experimental results from the boundary layer wind tunnel at the Slovak University of Technology in Bratislava. The optimal turbulence model and internal mesh settings were selected based on their statistical evaluation. For an evaluation of the critical directions of the wind flow around the ruin, the values of the external wind pressure coefficient were obtained from the selected calculation model and settings.</p> </abstract>ARTICLEtrue Investigation of the Performance of Buried Flexible Pipe in Reinforced Sand<abstract> <title style='display:none'>Abstract</title> <p>The experimental work of this study deals with the performance of pipe in sand with various responses subjected to incremental static loading where the backfill is reinforced with two types of reinforcement (geogrid and geocell) to investigate the effects of backfill cover. The pipes considered are installed in sand with different densities; i.e., loose, medium and dense sand, and a constant burial depth (2D, where D is the pipe diameter). It was concluded that the maximum deformation occurs at the crown of the pipe. The deformation increases when the sand density decreases. For a burial depth equal to 1.5 D, the maximum strain on the pipe crown increases by about 22.5% when the sand changes from dense to medium and 36.8% when it changes from dense to loose. The vertical stress above a pipe buried in loose sand is reduced by 8.3% when the geogrid width is 2B where B is the footing width, while it is equal to 22% when the geogrid width is B. When a geocell is used, the percent reduction is equal to 62%. The percent reduction in the vertical stress above a pipe buried in medium sand is about 28% when the geogrid width is 2B and 40% when the geogrid width is B and equal to 68% when the geocell is used.</p> </abstract>ARTICLEtrue Study of the Lightening of Concrete Through the Use of Recycled Tire Rubber and Expanded Clay Aggregate<abstract> <title style='display:none'>Abstract</title> <p>The waste of tire rubber is characterized by the generation of huge amounts, which is annually discarded. This waste causes problems for human health and the environment. Thus, the valorization of recycled tire rubber in concrete production is considered as an alternative and sustainable solution. This experimental work is a comparative study, which aims to investigate the possibility of using recycled tire rubber as a fine aggregate in the production of lightweight concrete. To achieve this objective, two types of lightweight concrete containing (35, 70 and 100%) of expanded clay and (5, 10 and 15%) of recycled tire rubber as a fine aggregate were produced. Their fresh properties were investigated using slump, density and air content tests, while the hardened properties were investigated by compressive strength, flexural strength, ultrasonic pulse velocity, and water absorption tests. The results obtained showed that the utilization of both expanded clay aggregate and recycled tire rubber leads to a reduction in density and mechanical strength but increases the porosity of lightweight concrete. However, the lightweight concrete containing the expanded clay aggregate had a higher efficiency factor than those containing recycled tire rubber.</p> </abstract>ARTICLEtrue of the Ramberg-Osgood Material Model for the Fire Design of Steel Members<abstract> <title style='display:none'>Abstract</title> <p>In this paper, the modified Ramberg-Osgood constitutive equations for calculating the stress-strain of steel at elevated temperatures using the parameters determined based on the transient state tensile test results achieved at the Helsinki University of Technology are verified. This is done by numerically comparing the global and local buckling capacities of I-shaped steel members incorporating the modified Ramberg-Osgood model along with the material model given in the fire section of Eurocode EN1993-1-2. For this purpose, a numerical model using the ABAQUS software was developed. Then, nonlinear analyses with imperfections (GMNIA) were performed to compare the buckling capacities of the steel columns and beams of four different hot-rolled cross-sections (IPE160, IPE180, HE100B, HE500B), made of steel grade S355, at three different temperatures (400°C, 500°C, 600°C). The results showed that adopting the modified Ramberg-Osgood model can lead to the same buckling capacities resulting when using the EN1993-1-2 material model for steel temperatures of less than 400°C. However, adopting this model for 600°C overestimates the buckling capacities in most cases.</p> </abstract>ARTICLEtrue of Indoor Air Quality in a Kindergarten<abstract> <title style='display:none'>Abstract</title> <p>Today in addition to the design of structures, layout solutions, and the design of suitable materials, the modern construction industry also addresses meeting the requirements for the energy performance of a building, with which the topic of the quality of the indoor environment is fully intertwined. Comfort in the use of buildings, and especially the provision of thermal comfort, is a fundamental aspect in the design of technical equipment systems, where a properly selected system regulating the indoor environment can affect b oth t he e nergy p erformance o f t he building and the quality of the indoor environment. One of the important factors is the air quality, where the main factor that af-fects the indoor environment is the concentration of CO<sub>2</sub>, whose value affects the biological functions of the human organism. The subject of this research is an evaluation of the indoor air quality in a kindergarten because children are more sensitive to environmental influences.</p> </abstract>ARTICLEtrue