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The paper deals with diagnostics, recalculation, and determination of the current load capacity of three concrete arch bridges on the original railway line Bratislava - Žilina. This was built in 1954 in connection with the relocation of the line, caused by the exhibition of the Nosice reservoir. At present, the railway line has been relocated to a new location and the existing original line, including the existing engineering facilities, will be used for the construction of a new road connecting the district towns of Púchov and Považská Bystrica. The task was solved within the cooperation of Faculty of Civil Engineering with the Railways of the Slovak Republic (ŽSR in Slovak) and the Research and Development Institute of Railways (VVÚŽ in Slovak). The conclusions from the recalculations and the subsequently determined load capacity show that the bridge structures in question are suitable for further use, however, their reconstruction is necessary.

The paper is focused on diagnostics and calculation of load-carrying capacity of the two atypical girder bridge objects on the railway line between Púchov and Považská Bystrica in Slovakia. These are skewness reinforced concrete (RC) girder bridges with three girders. The non-typicality is given by the fact that the spandrel girders are in the longitudinal direction, but the middle girder is relatively wide and is perpendicular to the clearance (not in the longitudinal direction). The diagnostics was performed on the objects aimed at determining the material and geometric characteristics, which served as a basis for the numerical model. A 3D scanner was also used to determine the geometric dimensions. The load-carrying capacity was subsequently determined on the bridges. The recalculation and diagnostics revealed the fact that bridge structures can still be used, but have to be reconstructed. This is a prime example of reusing in practice, i.e. how the old bridges can be further used, which means a significant saving of CO2 emission that would be produced by demolishing the old bridges and building new ones

Damage often develops in glued laminated timber members under high bending loads due to natural defects in the timber, which results in their low load-bearing capacity and stiffness. In order to improve the bending mechanical properties of glulam beams, a new type of longitudinal glulam reinforcement with pre-stressed basalt fibre-reinforced polymer composites (BFRP) was developed using the Near Surface Mounted (NSM) technique. The strengthening method consisted of two pre-stressed BFRP bars glued into the grooves at the bottom side of the beam; meanwhile, for the second strengthening alternative, the third BFRP bar was embedded into the groove at the top side of the beam. Therefore, an experimental study was carried out to verify this strengthening technique, in which fifteen full-size timber beams were tested with and without bonded BFRP bar reinforcement in three series. According to the results of this experimental study, it can be seen that the effective load-bearing capacity of the reinforced beams increased up to 36% and that the stiffness of the beams increased by 23% compared to the unreinforced beams. The tensile stresses in the wooden fibres were reduced by 11.32% and 25.42% on average for the beams reinforced with two and three BFRP bars, respectively. On the other hand, the compressive stresses were reduced by 16.53% and 32.10% compared to the unreinforced beams. The usual failure mode saw the cracking of the wood fibres at the defects, while for some specimens, there were also signs of cracks in the epoxy adhesive bond; however, the crack propagation was, overall, significantly reduced. The numerical calculations also show a good correlation with the experimental results. The difference in the results between the experimental and numerical analysis of the reinforced and unreinforced full-sized beams ranged between 3.63% and 11.45%.

The paper presents an extensive study aimed to determine the applicability of the demountable Bailey bridge (BB) system on construction sites or in other temporary conditions while meeting the regulations for the design and assessment of steel bridges. The analysis is focused on whether and to what extent the BB system with spans between 12 and 36 m is usable for on-site freight transport with conventional lorries with a total weight of up to 22–28 tons. At the same time, the BB system within these spans should be utilized for construction vehicles with a total weight of up to 32–40 tons. To calculate the load-carrying capacity, spatial numerical models were analysed using FEM and procedures of actual design codes were utilized. In the case of the main girders, analysis is focused on the out-of-plane stability of their compressed chords. Recommendations for the use of this bridge system in different arrangements of the main girder and bridge deck are then summarized and discussed.

In the case of prestressed concrete structures, information about the actual state of prestressing is an important basis for determining their load-carrying capacity as well as remaining service life. During the service life of the prestressed concrete structure, the initial level of prestressing is inevitably reduced as a result of the actions of various factors. These reductions of prestressing force are considered as prestress losses, which are influenced by construction stages, used materials, prestressing technology, or required length of service life. Available standards enable the determination of the expected values of prestress losses. Ultimately, their calculation is part of the design procedure of every prestressed concrete structure. However, aging and often neglected infrastructure in Europe is also exposed to factors, such as environmental distress, that are not considered in standard calculations. Therefore, verified and reliable methods for determining the actual state of prestressing are needed. This paper presents an experimental program of an indirect method for the evaluation of the value of prestressing force in seven prestressed concrete sleepers. Particularly, the non-destructive saw-cut method as a pivotal object of this study is performed and assessed. Furthermore, the Barkhausen noise technique is used as a comparative method. Subsequently, the experimental campaign is supported by the numerical analysis performed in the ATENA 3D software. Finally, the experimentally determined values of residual prestressing force are compared to the expected level of prestressing according to Eurocodes.

Structures and bridges are being designed on the proposed and requested design lifetime of 50 to 100 years. In practice, one can see that the real lifetime of structures and bridges is shorter in many cases, in some special cases extremely shorter. The reasons for the lifetime shortening can be increased of the load cases (e.g., due to traffic on bridges, or due to other uses of a structure), using the material of lower quality, implementation of new standards and codes according to Eurocode replacing older ones. During the whole lifetime the structures must be maintained to fulfil the code requests. If the constructions are not able to fulfil the Ultimate Limit States (ULS) and the Serviceability Limit State (SLS), the structures or bridges have to be strengthened (whole or its elements). The purpose of the paper is the presentation of using a layer of the fibre concrete for a columns&rsquo, strengthening. Using the fibre reinforced concrete (FRC) of higher tensile strength makes it possible to increase the load-bearing capacity of the cross-section the column. The contact between the old concrete (core of column) and newly added layer (around column) is very important for using that method of strengthening. In the article, there is also a comparison of the surface modification methods.

The optimisation of the design method for verification of slender steel beam-columns is still a current issue not only from scientific point of view, but also for design practice. Therefore, the main objective of this paper is comparison of the suitability of established design approaches, according to the European standards for steel and aluminium structures, on the basis of numerical simulations. Thus, a finite element model was validated on the basis of experimental analysis available in the scientific literature. To perform the comparison of accuracy of design approaches according to European standards, a commercial software program ANSYS was used for observation of the resistances of beam-columns. The resistance of european I beams with parallel flanges (IPE) and a rectangular hollow cross-section (RHS) were investigated for four load cases on a simply supported member and also on a pinned-fixed beam column with linear bending moment distribution, where the resistance of the cross-section governs. Finally, the conclusions for suitability of the respective design approaches are discussed, together with some findings that arose from this work.