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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

These elements are innovative and of interest to many researchers for the reinforcement of wooden elements. For the reinforced beam elements, the effect of the reinforcement factor, FRP and steel elastic modulus or FRP and steel arrangement of the reinforcement on the performance of the flexural elements was determined, followed by reading the load-displacement diagram of the reinforced beam elements. The finite element model was then developed and verified with the experimental results, which was mainly related to the fact that the general theory took into account the typical tensile failure mode, which can be used to predict the flexural strength of reinforced timber beams. From the tests, it was determined that reinforced timber beam elements had relatively ductile flexural strengths up to brittle tension for unreinforced elements. As for the reinforcements of FRP, the highest increase in load-bearing capacity was for carbon mats at 52.47%, with a reinforcement grade of 0.43%, while the lowest was for glass mats at 16.62% with a reinforcement grade of 0.22%. Basalt bars achieved the highest stiffness, followed by glass mats. Taking into account all the reinforcements used, the highest stiffness was demonstrated by the tests of the effectiveness of the reinforcement using 3 mm thick steel plates. For this configuration with a reinforcement percentage of 10%, this increase in load capacity was 79.48% and stiffness was 31.08%. The difference between the experimental and numerical results was within 3.62–27.36%, respectively.

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%.

Reinforced concrete (RC) structures are basically composite elements because they consist of two materials—concrete and reinforcement (reinforcing steel bars). From the point of view of the design of new constructions, it is necessary to design them in such a way as to ensure their reliability, safety and durability throughout their design lifetime, Td. However, all elements, including RC members, are affected by the environment in which they are located. An aggressive environment causes degradation of materials. In the case of reinforcement, corrosion of the reinforcement is considered to be the most well-known and at the same time the most serious way of degradation. From the point of view of existing reinforced concrete elements, it is therefore important to know whether and how the corrosion of the reinforcement affects the mechanical properties of the given reinforcement. The mechanical properties of reinforcement are very important when assessing the actual condition of reinforced concrete (RC) elements, to determine the resistance and load-carrying capacity of the elements. Therefore, it is necessary to investigate the effect of corrosion on mechanical properties of reinforcement. The paper reports on the results of an experimental analysis of the effect of corrosion on the change in the mechanical properties of reinforcement. Furthermore, it presents both the redistribution of mechanical properties along the cross-section of reinforcement, produced by various techniques, such as hot-rolling, hot-rolling with controlled cooling from rerolling temperature and cold-rolled as well as the mechanical properties under the action of corrosion.

The assessment of the resistance and remaining service life of precast prestressed concrete structures is becoming a crucial aspect of civil engineering. This fact is even more significant in the light of the first generation of precast prestressed concrete bridges’ failures in northern Slovakia. Recently, the collapse of a footbridge in Spisska Nova Ves underlined the need for proper diagnostic and assessment of existing prestressed concrete structures in Slovakia and abroad as well. Problematic precast prestressed concrete bridges of the first generation have been in service for more than sixty years, and thus knowledge of the current state of prestressing is the base for later determination of their load-carrying capacity. Hence, the present paper aims to introduce an overview of the present-day knowledge of indirect destructive and non-destructive methods for determining the state of prestressing in existing structures. Finally, the pros and cons of the mentioned techniques are discussed and compared.

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.

Railway bridges represent crucial points within railways, because of its strategy meanings in transportation infrastructure. During the decades of exploitation, degradation processes and external influences attack the bridge structures. Typical 70-years old riveted railway bridge with main plate girders and the upper member deck is analysed in the paper. Load-carrying capacity, possible reserves and analysis of critical details are presented. Provisions of the new guideline for determination of load-carrying capacities of railway bridges were applied. Data needed for numerical analysis and subsequent calculation were supported by enhanced diagnostics and measurements. Actual behaviour of the whole structure and chosen members, respectively, were verified by the static and the dynamic load tests. Both the researches academics from the university and the R&D institute staff of the state railway administrator were involved in this pilot project.

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.

When designing slender steel beam-columns, verification of their resistance have to satisfy design criterions according to approaches given in EN 1993-1-1. Torsten Hoglund (2014) also presented proposal for verification of beam-column resistance, which is based on design approach accepted in EN 1999-1-1, together with comparisons between these two standards on simply supported members subjected to compressive force and constant or linearly distributed bending moment. In this paper, further comparisons between these two approaches with different end conditions and different distribution of internal forces are presented.

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.

Verification of beam-column resistance can be accomplished according to design approaches given in EN 1993-1-1 [1]. These approaches are derived from verification of single span beam with pinned end conditions subjected to compression and bending moments. In the case of different end conditions, the application of those approaches is not so accurate and more difficult. Therefore, the comparison of verification according to above standard EN 1993-1-1 [1] as well as EN 1999-1-1 [2] to results of experimental analyses of beam-columns having pinned-fixed end conditions subjected to an eccentric compressive force simulating the behaviour of columns integrated into frames is presented in this paper.

The paper is focused on diagnostic and calculation of load-carrying capacity of bridge object in village Vitanova, Slovakia. The bridge is on the road II/520 connecting town Trstenná and village Suchá Hora near border with Poland and bypass the river Oravica. The bridge object was built in 1957, so, it was 60 years old bridge in time of calculation in 2017. It is reinforced concrete slab bridge of two single spans. In 2016, the Department of Structures and Bridges, the Faculty of Civil Engineering, University of Žilina, was asked to carry out the construction and technical survey and diagnostic of above mentioned bridge. The visual inspection, diagnostic, verifying real dimensions and material characteristics were requested. In 2017, the calculation of load-carrying capacity was done. For determining the load-carrying capacity, the standard approach given in Eurocodes was used. As an alternative, the modified (lower) reliability levels and their adequate partial safety factors according to Eurocodes were used.

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.

Recommended reliability levels and their adequate partial safety factors can be found in Eurocodes only for design of new structures and bridges. Modified reliability levels and partial safety factors for verifying bridge structures for their remaining lifetime were determined by theory of reliability at Department of Structures and Bridges at Civil Engineering Faculty, University of Žilina. This paper is focused on verification of modified partial safety factors of materials and load effects using calibration.