Marija Spasojević Šurdilović

This study examines the load–deflection response of continuous self-compacting concrete (SCC) beams incorporating recycled coarse aggregates. Nine two-span beams with reinforcement ratios of 0.65–0.94% were experimentally tested using 50% and 100% aggregate replacement. Recycled aggregate beams showed slightly reduced stiffness and increased post-cracking deflections, while ultimate load capacities remained comparable, particularly for 50% replacement. The influence of recycled aggregates was more pronounced at lower reinforcement ratios. Experimental ultimate loads exceeded EC2 and ACI 318 predictions, indicating effective moment redistribution and ductile behavior. The results confirm the structural applicability of high-quality recycled aggregates in continuous SCC beams.

This paper presents an experimental investigation on the flexural performance of continuous two-span reinforced concrete beams made with self-compacting concrete (SCC) incorporating natural and recycled coarse aggregates. A total of nine beams were tested under static loading conditions. The beams were divided into three groups based on different reinforcement ratios, and within each group, three aggregate replacement levels were used: 0%, 50%, and 100% recycled coarse aggregate. All beams were designed with identical cross-sections and subjected to two-point loading to simulate continuous support conditions. The study focused on evaluating cracking behavior, load–deflection response, and failure modes. The experimental results highlight that partial replacement with recycled aggregates (RAC50) can achieve comparable or even improved mechanical performance compared to natural aggregate beams, including enhanced compressive strength and ductility. Beams with 100% recycled aggregates (RAC100) showed slightly higher deflections and earlier crack initiation, particularly at lower reinforcement ratios, although overall flexural behavior remained consistent with natural aggregate concrete (NAC) beams. It was also observed that as reinforcement ratio increases, the influence of aggregate type diminishes, indicating that steel reinforcement predominantly governs the structural response at higher ratios. Crack widths and propagation patterns were systematically monitored, confirming that RAC beams maintain acceptable deformation and ductility under load. These findings emphasize the feasibility of using high-quality recycled aggregates in structural SCC elements, providing a sustainable alternative without compromising performance, and offering guidance for the design of continuous RAC beams.

This paper presents a comparative analysis of the design and verification of an existing steel industrial building according to traditional JUS standards, based on the allowable stress method, and current Eurocode (EC) standards, based on the limit state concept. Although existing structures designed according to JUS standards have generally performed satisfactorily, stricter Eurocode load combinations, partial safety factors, and stability criteria may result in non-compliance with current requirements. The objective of this study is to identify the key differences between the two design approaches, determine the critical structural members that do not satisfy Eurocode requirements, and consider appropriate strengthening measures for adapting the existing structure to current engineering standards.

Modern architectural solutions in densely populated areas require structures with multiple underground levels. With advancements in construction technology, numerous solutions have been developed to secure the excavation of foundation pits and adjacent structures. The most rational solution adopted is the securing of the excavation and adjacent structures with reinforced concrete diaphragm walls supported by steel struts at two levels. The paper outlines the specifics of the structural solution, with a detailed analysis of the steel struts. Special emphasis is placed on the stability control of the struts, which was conducted using various methods outlined in Eurocode 3. The control of flexural buckling was performed through the application of the equivalent column method, the use of equivalent geometric imperfections, and the implementation of both geometrically and materially nonlinear analysis with imperfections.

This paper analyzes the influence of high damping rubber bearings (HDRB) on the dynamic response of a reinforced concrete frame structure under earthquake excitation. Both base-isolated and fixed-base structures are considered, as well as regular and irregular configurations in plan and elevation. A comparative analysis was carried out for natural periods of vibration, base shear forces, maximum horizontal displacements, interstory drifts, and the occurrence of plastic hinges. Conclusions were drawn on the effectiveness of HDRB application and the impact of structural regularity on the dynamic response during seismic loading.

The subject of this paper is the vibration analysis of steel beams with hexagonal web openings. In addition to verifying the limit states of existing structures where new web openings are introduced, beams with web openings are also used in newly planned structures. This paper presents a comparative analysis of serviceability limit state calculation methods according to the methods provided in prEN 1993-1-13. A comparative calculation of natural frequencies of oscillation is analyzed, as this represents the main parameter for assessing structural vibrations.

The behavior of welded steel I-girders presents a complex stability and elastic-plastic problem. The girders are loaded over a short length of the flange and within the plane of the web, under either concentrated or uniformly distributed loads, commonly referred to as patch loading. This study analyzes welded steel I-girders both with and without longitudinal web stiffening. The girders, or sections of the girders, are not perfectly flat in terms of their geometry, and the materials from which the girders are made exhibit certain deviations, referred to as geometric and structural imperfections. These imperfections can influence the behavior of the girders, and they are accounted for in this research. The load was progressively increased until the ultimate load capacity was reached, which was characterized by the buckling of the web. The analysis was conducted using the ANSYS software package, and the results were compared with experimental data from the literature.

The aspect of resonant vibrations due to pedestrian movement is of great significance in engineering practice. Therefore, understanding the variations in the natural frequency of bridge structures under varying positions of additional mass is of particular interest. This paper presents a procedure for the straightforward determination of the natural frequencies of a beam pedestrian bridge for various positions of pedestrians or a service vehicle based on derived analytical solutions. The calculation takes into account the inertial effects of the additional load mass, modeled as either uniformly distributed or concentrated. The importance of additional load mass effects on the fundamental frequency of a beam pedestrian bridge and its dynamic response to a moving pedestrian load is demonstrated on a bridge example. The proposed solutions are also applicable to other girder system structures with uniform mass and stiffness along their span.

This paper introduces algorithms for computer-aided calculation, based on a proposed computational model for stay cables, decomposed from a bridge’s structural system. These algorithms determine the necessary tension forces and corresponding deformations in the cables for individual strand tensioning using lightweight hydraulic jacks. Two tensioning methods are discussed: the first involves single-cycle tensioning with varying force intensities, while the second employs multiple cycles by applying forces of constant intensity until achieving an equalization of forces in all strands of the cable. The efficiency of the proposed procedures is demonstrated through a numerical example.

Welded structural hollow sections are becoming increasingly used in contemporary civil engineering buildings. More specific design techniques are needed for connections in steel structures with welded structural hollow sections than for traditional connections made with gusset plates. At the connecting site, stress and local deformations show very complex, non-linear behaviors. The application of non-linear numerical analyses to determine the ultimate bearing capacity of “T” connections was demonstrated in this study. A non-linear material model was used in the analysis. In order to validate the applicable steel modeling method, a comparative study between experimentally obtained results and analytically and numerically computed ultimate bearing capacities was carried out. The comparison showed good agreement between the numerical and experimental results and pointed out the highly conservative design of such joints was obtained using the analytical solution.