Advances in Science and Technology Vol. 176

Abstract: This article follows earlier publications dealing with reinforced concrete arch overpasses on the D3 0311 motorway section located near Ceske Budejovice, Czech Republic, close to the Austrian border. While previous work provided a basic overview of the bridge’s structural layout and construction, this article focuses on a detailed static analysis and related assessments. Attention is given to serviceability limit states and stability, as well as to the analysis of the construction stages and its possible alternatives. A detailed description of the results from static load testing, including the monitoring of crack initiation and propagation, is presented. The study also addresses the problem of differential shrinkage in the concrete at the arch-deck interface. The results demonstrate that detailed numerical analysis combined with experimental verification through static load testing provides valuable insight for optimizing design and ensuring long-term reliability of these bridge structures.

Abstract: The topic of medium-span bridges combined with longitudinal segmentation of the structure using precast components made of UHPC material was a challenge for the grant research team. The researchers' goal was to optimize the shape of the parapet beam from both a structural and architectural perspective. It was necessary to find the most suitable solution for connecting the beams to the bridge deck and to design the technology for manufacturing the individual structural elements and connecting them into a single functional unit. All this had to be done with an emphasis on maintaining the required parameters for safe and secure operation of the structure.The article presents a new Medium Span Footbridge System (MSFS) with a span of up to 30 meters. The system consists of a combination of parapet beams with longitudinal prestressing, ribbed bridge deck slabs, and grout joints. The article mentions the static analysis of the structure. The method of manufacturing individual parts is documented, together with the specific procedure for constructing the footbridge, which is designed to minimize work on the construction site while minimizing traffic restrictions under the footbridge under construction. The article also presents a functional sample of the structure – the first medium-span footbridge (MSF) made of UHPC with a span of 26.0 m and a clear width of 3.0 m.

Abstract: Massive structures are exposed to the risk of high temperatures due to cement hydration. With the requirement for sustainable development, the clinker content of conventionally manufactured cements is being reduced, resulting in the development of blended cements, which are gradually being introduced into production. Therefore, the development of temperatures in massive concrete structures containing modern blended cement is the subject of an experimental program. Its results are evaluated not only in terms of the properties of the resulting concrete, but also in terms of the possibility of concrete production and the technology of mixing. Finally, recommendations are given for the design of concrete mixtures for massive structures. Furthermore, the article deals with the comparison of the measured values with the thermal analysis of the structures.

Abstract: UHPC (“UHPC” will be used in the paper for UHPFRC with steel fibres) offers great potential in terms of extending the service life of structures and reducing material consumption in bridge construction. One way to achieve the economical application of UHPC is to mechanically connect optimized UHPC structures with other structural elements made of conventional materials into a single functional unit. This paper describes the development of a structural system that provides effective use of the properties of UHPC and conventional concrete. An innovative coupling element made of UHPC material was developed for the connection. During development, computational and experimental analyses were performed, including static and fatigue resistance tests of the coupling and full-scale load tests of a prototype bridge girder. The article briefly summarizes the individual parts of the research and presents its results.

Abstract: The aim of this article is to compare the punching shear resistance of flat slabs without shear reinforcement, obtained from experiments, with the results of nonlinear analysis and the second generation of Eurocode 2. The experiments were conducted at the Slovak University of Technology over the past few years. The article deals with five axisymmetric full-scale flat slabs with dimensions of 2.50 × 2.50 m, each with a varying reinforcement ratio. The tested specimens had thicknesses ranging from 180 to 250 mm and were supported by square or circular columns with side lengths or diameters ranging from 200 to 300 mm.Subsequently, a nonlinear analysis of these specimens was carried out using the ATENA software. The results from the experiments and the nonlinear finite element analysis (NLFEA) were then compared with the predicted punching shear capacities according to the second generation of EC2. The punching shear resistances obtained from the tests show good agreement with the predictions by the EC2 (2023) and NLFEA when the CoV of the ratio V_R,exp/V_R,model reached a value of 0.05 in the case of NLFEA and 0.057 with the EC2 (2023) model. However, the results from the nonlinear analysis indicate differences in the deformation of the slabs at the failure load.

Abstract: The presented study focuses on the theoretical and experimental analysis of slabs with non-metallic GFRP (glass fiber reinforced polymer) bars as a prestressing reinforcement in concrete structures [25]. In this study, experimentally designed GFRP-reinforced prestressed concrete slabs were developed as a lost formwork on the bridge girders. Using prestressed GFRP could effectively minimize thickness, reduce crack widths, improve flexural performance, and lower the deflections of the slabs. Due to the corrosion-resistant behavior of GFRP, it is possible to minimize the thickness of the slab by reducing the concrete cover, which leads to a reduction in the self-weight of the member. Members with GFRP reinforcements deformed approximately linearly under increasing load. The first elastic part with no cracks observed during loading is typical for small increments of deflection within the rising bending moment. The stiffness of the member reduces after crack formation. The second part of the diagram is called linear-elastic, with increasing deflection of the slab due to the linear-elastic behavior of GFRP. The results obtained were compared with analytical models for ultimate flexural resistance and load deflection behavior at each loading step evaluated using the design equations introduced in ACI 440.1R-15 and ACI 440.4R-04. For a non-linear analysis software for FEM, Atena was used, which considered geometrical and physical non-linearity. The differences in the analytically calculated models to estimate the bending capacity and deflections in the middle span of the prestressed slabs with experimental results and nonlinear FEM analysis were evaluated.

Abstract: This paper presents the numerical modeling of a reinforced concrete deep beam (DB) with dimensions of 1100mm, 400mm, and 150mm under two-point loading conditions using the same reinforcement technique. The study evaluates specimens cast from three distinct concrete types: normal-weight concrete (NWC), lightweight concrete (LWC), and high-strength concrete (HSC), while maintaining identical reinforcement configurations. The analysis indicates that the concrete grade significantly influences the ultimate load-bearing capacity of the members. Specifically, the LWC specimens exhibited a 40–41% reduction in capacity compared to the NWC specimens. Conversely, the NWC beams demonstrated a 15–21% lower capacity than the HSC beams. Despite these variations in peak load, all specimens displayed similar failure mechanisms and crack propagation patterns. A comparison between the numerical results and experimental data showed strong correlation, validating the accuracy of the proposed model.

Abstract: In prestressed elements with shear reinforcement, according to the current design procedures EN 1992-1-1 (2004), the effect of axial force is taken into account by using a lower angle θ of the compression concrete strut compared to reinforced concrete elements. However, there is no direct procedure for calculating this angle and it is up to the experience and discretion of the designer, who may take into account the recommendations of the authors of professional publications. The article deals with the theoretical evaluation and experimental load test of the shear resistance of prestressed beams. It examines the effect of axial force on the shear resistance with shear reinforcement, which in the analyzed element is greater than that defined by the minimum degree. The theoretical analysis evaluates the approach of the design model for shear with shear reinforcement according to EN 1992-1-1 with experimentally obtained values. The analysis is also based on the results of an experimental campaign. The beam with a standardized cross-section, which is still used today for concrete road bridge structures, was tested. The full-scale experiment was therefore carried out on a 600 mm high beam with an I-shaped cross-section. The total length of the experimental beam was 7.0 m, while the effective span of the beam during testing was 4.9 m, which allowed obtaining 2 results from testing one element. The result is the demonstration of a positive influence of axial force on the shear resistance of an element with shear reinforcement, although the level of influence is not significant.

Abstract: Fiber-reinforced polymers (FRP) have been used for decades in aerospace, sports, the automotive industry, and other sectors. In the construction field, they found their application in the early 1950s. Typically, they are used in structures as direct reinforcement in areas with aggressive or chemically demanding environments. This paper focuses on glass fiber-reinforced polymer (GFRP) stirrups combined with longitudinal GFRP reinforcement in elements. It explores the possibility of an alternative solution to traditional steel reinforcement in concrete structures. This application would be suitable, for example, on bridges exposed to an aggressive environment containing chlorides from de-icing salts, where stirrups are the first to corrode after the concrete cover is damaged by carbonation, due to their position closest to the surface.The article is primarily focused on the assessment of the shear resistance of a concrete element reinforced with GFRP shear reinforcement. It is relatively problematic to develop a calculation model that would correctly capture the effect of GFRP stirrups on shear resistance, as well as the decrease in the tensile strength of the stirrups at the bend location. The analysis in this paper deals with determining the predicted shear resistance of a concrete element reinforced purely with GFRP reinforcement and comparing these values with experimentally measured values from a selected experimental study. The article compares the measured results with the experiment, with the most accurate agreement achieved by the results according to EN 1992-1-1:2023 and ACI 440.11-22. The shear resistance calculated by the CNR-DT 203/2006 standard was higher, thereby significantly overestimating the capacity compared to the experimental results. The updated version, CNR-DT 203/R1/2025, provides relatively accurate results that can be considered acceptable for practical use. Conversely, the values calculated by the CSA S806-12 and AFGC standards are significantly lower, meaning they substantially underestimated the shear resistance of the beams.