Archives for Technical Sciences最新文献

The bridge's span structure comprises a connected beam designed to support a concrete slab poured over parallel steel supports. Simultaneously, segmental construction, shrinkage, and the flow of concrete play a significant role in stress redistribution over time. The span construction is statically indeterminate due to its connections with the abutments, and temporal deformations occur under additional complex conditions. In this analysis, we employed a calculation model based on the layered finite elements method developed by the authors. This model can be utilized to analyse both statically indeterminate supports and the predicted phased construction method. It accounts for changes in the static system and loading, as well as variations in the layers within the coupled section and the viscous properties of the concrete over time. The calculation analysis results reveal that viscous concrete deformations, combined with different moments of activation of individual segments, have a significant impact on stress redistribution over time. Such intricate analyses are indispensable for ensuring the required safety and cost-effectiveness of the bridge span construction.

Complexity of geological terrain built demands different level of research in order to obtain all necessary characteristics for the establishing of connections between the structure of the objects and the terrain. Frequent changes of rocks in vertical profile and their irregular settling related to creasing of the terrain during geological history makes choosing representative parameters harder. Layers of similar characteristics that are interconnected are separated into geological environments by taking medium values of the parameters within that environment.

During the research, for the purpose of constructing of the silos objects, boreholes were drilled in the axis of each silos to a depth of 10.0 m. In a small area, there is a complex structure of the terrain, which, in addition to changes in the lithological composition, is also dictated by tectonic activity. Directly in the hinterland of the research conducted with boreholes, there is an open terrain profile with a height of about 6.0 m. By connecting the layers from the investigation works and the open profile on the terrain, a clearer picture of their position on the narrow part of the terrain was obtained.

Frequent changes of layers of marly rocks and sandstones and their synclinal deposition demanded separation of certain geological environments with layers of the same characteristics. In addition to taking samples for laboratory tests, field tests of the solubility of marly rocks in the void at different temperatures were also conducted. In parallel with the samples from the investigation works, samples from the open terrain profile were examined. The results showed a shorter dissolution time of marly rocks from the open terrain profile compared to the same rocks taken from the core of the borehole.

Urban public spaces play a crucial role in holding various public events. Although events positively enrich the urban environment and encourage real social interactions, there are no guidelines for their spatial organization, posing a challenge in terms of using public spaces. This paper introduces new classifications of public events and temporary structures intended for their maintenance, applied to investigate their role and impact on urban spaces, using Liberty Square in Novi Sad as a case study. This research provides valuable insights for improving urban planning, considering the need for a balance between events and preserving the quality of urban spaces.

The main subject of this manuscript is mountain streams used by construction of small hydro power plants. The motivation for this research stemmed from a number of conflicting opinions about the justification of the construction of small hydropower plants and their facilities. This research encompasses different methods for the analysis of the justification of the construction of a small hydropower plant, starting from tradition in correlation with water mills, through a techno-economic approach to a complex multi-criteria research model. All methods are represented by objective formulas.

World experiences are also presented, through the level of potential utilization, compared to the degree of development. The possible positive and negative impacts of the construction of such facilities for the exploitation of the potential of small watercourses were analyzed. After the conducted research, and with respect to the principle of minimum energy, which has become the paradigm of modern civilization, it can be concluded that using the potential of small watercourses by building small hydropower plants belongs to the domain of using renewable energy sources and that it is a function of sustainable development.

Decision makers are recommended to exclusively apply a multi-criteria methodology, which can holistically include all technical, economic, environmental, social and other non-profitable but important impacts.

As a result of the planned change of use, the imposed load on the existing reinforced concrete mezzanine slab will be significantly increased, wherefore a diagnostics and assessment of the current state of the structure has been carried out. The control calculation showed that the slab does not have sufficient bearing capacity for the increased load. After qualitative analysis of possible strengthening methods, two methods were selected for detailed analysis: strengthening with steel strips and strengthening with carbon fiber-reinforced polimer (CFRP) plates.

The criterion for choosing the optimal solution was the total cost of the material. It has been shown that the total price of materials for strengthening with steel strips is almost 40% lower than the price of strengthening with CFRP plates. It has also been observed that, when using steel strips, the contribution of the price of adhesive in the total cost of material is extremely high. When varying the level of strengthening, for imposed loads from 3 to 7.5 kN/m2, the ratio of the total costs of materials for steel and CFRP strips ranges between 60 and 73% and shows a slight tendency to increase with the increasment of loads.

Thermal comfort of urban areas is a highly researched field of science, which is gaining more and more importance in the field of ecology. The research of the area from the aspect of the convenience of physical activities and outdoor life provides data that is also useful in the health sector. This research included the area of Semberija in Bosnia and Herzegovina, which is characterized by unfavorable conditions during summer, due to high temperatures, swampy land and increased artificial presence of construction and industries.

Not all areas have the same weather conditions, therefore other factors such as relief and presence of forests are important in the overall state of the area. Therefore, data from two meteorological stations, at a short distance from each other, but in a different natural and artificial environment, were analyzed. These are the station in the town of Bijeljina and the station within the Mine and Thermal Power Plant in Ugljevik.

Within this research, the WBGT bioclimatic model was used, which is widely used in the world for the purposes of calculating the time that the human body can spend in direct sunlight during work or exercise, without rest. Given that the same time period is not covered, an average of 14 years (period 2005 – 2018) was analyzed for the area of Bijeljina, and an average of 8 years (period 2015 – 2022) for Ugljevik. The period from 2015 to 2018, which covers both locations, was also analyzed in order to make a comparison and notice the differences and determine the factors that affect the thermal comfort of the space.

Using limited materials for numerical modeling of structural samples and comparing the behavior of samples with each other in order to reduce the number of straw test samples in order to reduce laboratory costs is one of the best methods today. ANSYS is one of the finite element software that is used for modeling reinforced concrete elements by Solid65 element. As a case study, a concrete-filled steel column under cyclic loading is examined and the best value for the Crushed Stiffness Factor (CSTIF) parameter that is one of Solid65 element parameters is suggested to confirm the modeling. By investigating the results, it can be concluded that this parameter is one of the most important factors that plays a significant role in convergence in ANSYS software for modeling CFT columns.

The aim of this study is to identify and map the zones of different vulnerability to flash floods based on the geospatial analysis of natural conditions in the Porečka River basin (Republic of Serbia). The analysis covers the catchment area of the Porečka River (493.82 km2 ). Geospatial analysis was conducted using GIS software (QGIS 3.18). The Flash Flood Potential Index (FFPI) was used to determine the terrain's predisposition to flash floods, where the input data for determining the value of the index were the values of the following coefficients: the terrain slope, the type of geological substrate, the way of land use, and the bareness of the terrain.

The analysis determined that 50.43% of the total territory of the basin belongs to the class of high and very high susceptibility to flash floods, and when looking at the length of watercourses in the basin, that percentage is 81.94%. The results of this study clearly indicate the advantages of using modern GIS technologies in the land use and risk management. Geospatial analysis is of particular importance in the field of managing regions that stand out as particularly vulnerable to some natural disasters. 

Vehicle classification is a crucial task owing to vehicles' diverse and intricate features, such as edges, colors, shadows, corners, and textures. The accurate classification of vehicles enables their detection and identification on roads and facilitates the development of an electronic tollcollection system for smart cities. Furthermore, vehicle classification is useful for traffic signal control strategy. However, achieving accurate vehicle classification poses significant challenges due to the limited processing time for real-time applications, image resolution, illumination variations in the video, and other interferences. This study proposes a method for automated automobile detection, recognition, and classification using statistics derived from approximately 11,000 images. We employ SURF-based detection and different classifiers to categorize vehicles into three groups. The Traffic Management System (TMS) is crucial for studying mobility and smart cities. Our study achieves a high automobile classification rate of 91% with the medium Gaussian Support Vector Machine (SVM) classifier. The paper's main objective is to analyze five object classifiers for vehicle recognition: Decision Tree, Discriminant Analysis, SVM, K-Nearest Neighbor Classifier (KNN), and Ensemble Classifier. In the discussion section, we present the limitations of our work and provide insights into future research directions.