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Abstract Dynamic compaction is a soil improvement technique which involves the repeated application of an impact load to a contact area of the soil surface induced by heavy weights. Experimental measurements were prepared for evaluation of the ground wave propagation induced by the rapid impact compaction. Influence of increase of subsoil stiffness during compaction and terrain configuration were investigated. When the shear strength of soil is exceeded during the penetration of the compaction footing, increase of peak particle velocities is slower but still clearly visible along the measurement line. The peak particle velocity is damped by the subsoil below 5 mm s−1 within 40–50 m from the source of excitation. Attenuation radius is affected by the terrain configuration, when terrain elevations cause the increase of acceleration amplitudes. Rigid bodies in the ground, such as foundation structures, could have similar influence. Dominant frequencies are in the interval from 20 to 40 Hz regardless the distance from the source of excitation or the density of the treated subsoil. Obtained results are preferably related to the given boundary conditions. However, wave propagation pattern and change of its characteristics during densification of the subsoil are applicable at another construction sites considering their particularities.

This article presents the results of tests carried out to assess the condition of PP-modified concrete. The tests were carried out on samples previously stored at ambient temperature and exposed to temperatures corresponding to fire conditions—300 °C, 450 °C, and 600 °C. Axial compression tests of cube-shaped samples and three-point bending of beams were carried out. During strength tests, acoustic emission (AE) signals were recorded and the force and deformation were measured. Recorded AE events were clustered using the k-means algorithm. The analysis of the test results allowed for the identification of signals characteristic of the individual stages of the material destruction process. Differences in the methods of destruction of samples stored in ambient conditions and those exposed to fire temperatures were also indicated. While loading the samples, measurements were carried out using the digital image correlation (DIC) method, which enabled the determination of displacements. Based on the results of the laboratory tests, a numerical model was developed. The results obtained using different research methods (DIC and FEM) were compared. Tomographic examinations and observations of the microstructure of the tested materials were also carried out. The analyses carried out allowed for a reliable assessment of the possibility of using the acoustic emission method to detect destructive processes and assess the technical condition of PP-modified concrete. It was confirmed that the acoustic emission method, due to differences at low load levels, can be a useful technique for assessing the condition of PP-modified concrete after exposure to fire temperatures. So far, no research directions in a similar field have been identified.

In addition to traditional building materials, such as steel and concrete, wood has been gaining increasing prominence in recent years. In the past, the use of wood was limited due to its susceptibility to damage by fungi, insects, and temperature. These shortcomings were gradually eliminated as the quality of wood processing increased and thanks to modern high-quality insulating and protective materials. The return to the utilisation of this natural building material was also supported by the development of new wood-based materials, such as glued laminated wood, and new types of mechanical fasteners, as well as by the introduction of new design methods provided in the Eurocodes. Within this context, this paper focuses on using wood in transport infrastructure, especially as the basic material for footbridges and small road bridges. Combined timber–steel bridges emerge as a very effective type of superstructure in contemporary road bridges and footbridges, especially in areas with natural exposure. Usually, wood is used for the main bridge girders, while steel is preferred for bridge deck elements—stringers and cross-girders. The results of this parametric study offer optimal structural solutions for footbridges with spans of 12.0–24.0 m, reflecting satisfactory static and dynamic footbridge behaviour. Particular attention is paid to a problematic structural detail—the connection between the steel cross-girder and the timber main girder. Firstly, this connection’s characteristics were measured experimentally using nine laboratory samples made of two glued laminated timber blocks, simulating main girders connected with a hot-rolled steel cross-girder. The connection was prepared in three variants, with different heights of the end plates and different numbers of bolts. Subsequently, these characteristics were computed using two numerical FEM models. The first model was created using SCIA Engineer software with a combination of shell and beam finite elements. The second, more sophisticated model was created in the ANSYS software environment using 3D finite elements, allowing us to better take into account the plasticity and orthotropic properties of wood and the points of contact between the individual members. Finally, the experimental results produced by sample testing in the laboratory were compared to the outputs of FEM numerical studies.

The use of composite precast or steel bars as reinforcements for timber beams is an important technique that can improve effectiveness or allow cross sections to be reduced. This paper presents experimental, theoretical, and numerical studies of full-size timber beams measuring 82 × 162 × 3650 mm3 using prestressed steel bars and 10 mm diameter basalt and glass bars with a prestress of 10 MPa. In addition, parametric studies were carried out using FEM numerical simulations. In the experimental tests, an increase in load-bearing capacity and stiffness of up to 58% and 10.7% for steel bars, 32% and 10.1% for basalt bars, and 27% and 7.8% for glass bars, respectively, was obtained compared to unreinforced beams. The different levels of improvement in reinforcement efficiency was also related to the different elastic modulus of the reinforcement itself. Unreinforced beams showed a linear elastic range. In contrast, on beams reinforced with steel bars, the curve had a slightly steeper line than the control beam, and the slope of the curve then decreased when a certain load was reached. All beams failed when the lower wood fibers reached maximum tensile strain. The allowable compressive strain then decreased by 36.6% for basalt bars, 32.9% for glass bars, and 30.4% for steel bars. The use of prestressing further exploited the strength of the reinforcement beyond the yield point. All unreinforced beams primarily failed in the tension zone due to fracture of the timber fibers. Prestressed and reinforced beams were already failing due to bending and shear. The experimental and numerical analysis was also compared, and the results showed a good agreement and a maximum difference of approximately 5.7%.

This article presents the results of tests conducted to identify the failure process and evaluate the deformation of axially compressed concrete specimens modified with polypropylene fibers (PP). The test specimens were previously stored at ambient temperature and subjected to fire temperatures of 300 °C, 450 °C, and 600 °C. Acoustic emission (AE) signals were recorded during loading, along with force and strain measurements. The recorded AE signals were analyzed using the k-means clustering method. The compilation of the test results made it possible to determine the classes of signals characteristic of different stages of the material failure process and to indicate the differences in the failure mechanisms of specimens stored under ambient conditions and subjected to fire temperatures. Digital image correlation (DIC) measurements were conducted during the strength tests. A numerical model of the material (FEM) was also prepared, and a comparison of the obtained results was carried out.

Components of civil buildings are frequently made of low-alloyed steel, which can suffer from corrosion damage. This damage reduces their bearing capacity and/or redistributes the load to neighboring regions with the potential risk of their collapse. For this reason, this study deals with the non-destructive monitoring of bodies made of these steels based on Barkhausen noise emission. The superimposing contribution of corrosion extent and exerted tensile load is investigated on samples of variable yield strength in the range from 235 to 1100 MPa. It is found that the presence of a corroded layer attenuates Barkhausen noise and makes the body harder from a magnetic point of view. The reduced effective thickness of the samples as a result of corrosion damage increases the true stress. Barkhausen noise grows along with the tensile stress in the direction of exerted stress at the expense of decreasing Barkhausen noise in the perpendicular direction. The evolution of Barkhausen noise versus tensile stress is mostly shifted to the lower values of Barkhausen noise, along with the increasing degree of corrosion damage. The evolution of Barkhausen noise versus tensile stress is also affected by the initial microstructure and the corresponding yield strength of the low-alloyed steel. Corrosion attack results in the growth of FWHM, which is compensated by the decreasing evolution along with the tensile stresses. The effective values drop down with the higher extent of corrosion damage. However, the response with respect to the tensile stress is asymmetric in RD and TD due to the realignment of DWs into RD. Finally, PP tends to increase with the corrosion attack as well as the tensile stress and this parameter only exhibits the systematic behavior in RD as well as TD. On the other hand, MBN-extracted parameters as well as their combination provide no exclusive values on which the pure contribution of corrosion and tensile stress can be distinguished.

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.

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.

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%.

In the case of existing 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 lifetime. This is even more important in the case of existing prestressed concrete bridges, which are exposed to a more aggressive environment than the other prestressed concrete structures. The level of prestressing is affected and reduced by prestress losses at a given time. In calculating the internal forces and stresses, required for the assessment of the Ultimate Limit State and the Serviceability Limit State, it is necessary to know not only the prestressing level but also the cross-sectional area of the prestressing steel (wire, strand or cable), which can change in time due to corrosion. In practice, in the case of the pre-tensioned concrete members, it has often happened in the past that cable ducts have been grouted only partially, or not at all, due to poor grouting technology. Experts did not realize what this could cause in the future—the penetration of water with aggressive agents directly into the cable duct and consequently corrosion of the prestressing steel, which means not increased protection of the steel, but rather acceleration of degradation. On the other hand, in many cases, corrosion also occurs in ducts that are not grouted and no water has entered them. This paper deals with this phenomenon—the formation of corrosion of prestressing steel in cable ducts in ungrouted ducts due to moisture. This problem was investigated experimentally and numerically in the simulation program ESP-r. Experimental measurements and numerical simulations have shown that the water vapor condenses in the cable ducts, which can subsequently cause corrosion of the prestressing steel.

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.

This paper investigates the potential of a non-destructive magnetic technique based on Barkhausen noise emission for the monitoring of prestressing bars with respect to their undesired over-stressing. Barkhausen noise signals are correlated with tensile stress, residual stresses, and microhardness measurements. It was found that prestressing bars exhibit strong magnetic anisotropy which becomes more pronounced along with the increasing degree of the bar’s over-stressing. Barkhausen noise emission becomes strongly attenuated in the direction of the tensile stress at the expense of the perpendicular direction. However, the Barkhausen noise emission in the direction of the tensile stress exhibits a continuous and remarkable decrease, whereas the Barkhausen noise steep increase for lower degrees of over-stressing is followed by early saturation for higher over-stressing. This study demonstrates that the Barkhausen noise technique is capable of distinguishing between the prestressing bars loaded below yielding, and those which are over-stressed.

Reliability is one of the most significant requirements for structures given in Eurocodes. Thus, the specific level of safety, serviceability, and durability have to be satisfied to fulfill the reliability of structures. In the case of reinforced concrete (RC) members, the corrosion of reinforcement is not assumed in the stage of structure design, which is in contrast with the structures in service, where the corrosion of reinforcement can significantly decrease their diameter ø in time. In these cases, the moment resistance in time MRd(t) decreases during the designed lifetime Td of a structure. The corrosion speed is as a basis for the calculation of moment resistance in time MRd(t), i.e., a first-year corrosion rate rcorr and a corrosion model as well. The corrosion itself is a very complicated issue, so the first-year corrosion rate rcorr and also the corrosion model can be different under various conditions in Slovakia. The paper is focused not only to determine the corrosion speed (first-year corrosion rate rcorr and the corrosion model) and parametric study of the moment resistance in time MRd(t) under various conditions in Slovakia but also shows an overview on some parameters that may influence the corrosion process.

This paper deals with the assessment of a real prestressed tendon by the use of Barkhausen noise emission. The tendon was obtained from a real highway bridge after 33 years in service. Barkhausen noise is studied as a function of the stress state, and the Barkhausen noise signals received directly from the tendon on the real bridge are compared with the Barkhausen noise signals received from the tendon during loading in the laboratory. Assessment of the prestressing is based on the analysis of the effective value of the Barkhausen noise signal as well as the position in which the Barkhausen noise envelopes attain a maximum.

The tempcore process is implemented in rolling mills to produce high strength reinforcing steel. Besides being used as reinforcement, rebars are also used as the base material for the manufacturing of anchor bolts. The mechanical properties of reinforcement bars used in Europe are assessed in accordance with Eurocode without the recommendations for cast-in anchor bolts. The material properties of Tempcore rebars are not homogenous over the bar cross section. The European Assessment Document (EAD) for the cast-in anchor bolts does not exactly specify the mechanical properties of the thread part. The aim of these experiments is to show the different mechanical properties of rebars and their thread parts. The experiments were performed on rebars modified by peeling to characterize the reduction of diameter in a thread part. As a possible way to predict mechanical properties in a non-destructive way, the hardness tests were performed. Next, the application of the correlation relationship between hardness and tensile strength has been determined. The paper formulates preliminary recommendations for assessment of the cast-in anchor bolts in practice.

Real bridge structures are affected by environmental conditions. The environmental loads in time cause the degradation of concrete and reinforcement. The diagnostics of real state of existing bridges are very important due to actual degradation and corrosion. In the frame of research activities of Department of Structures and Bridges, Civil Engineering Faculty, University of Žilina, the real bridge structure was observed for a few years. It is girder reinforced concrete bridge near town of Žilina in Slovakia. The results of diagnostics which focused on reinforcement corrosion are presented. The paper deals with reinforcement corrosion and its influence on the moment resistance of the existing concrete structures.

Ageing infrastructure leads to the need for a proper assessment and final decisions considering its state. In the case of prestressed concrete structures, knowledge of the residual state of prestressing is the crucial factor. Therefore, reliable diagnostic techniques for determining the residual value of the prestressing force are needed. This information is subsequently used in the process of the quantification of the load-carrying capacity and remaining service life of prestressed concrete structures. The presented paper introduces an evaluation of a monolithic 62-year-old prestressed concrete bridge, which was built in 1959. The assessment was carried out as a result of concerns after exposure of the anchorage area of the bridge, which was executed during the construction of the new system of anti-flood barriers in the town of Banska Bystrica in central Slovakia. Therefore, the diagnostic survey and subsequent determination of the residual prestressing force included the application of the saw-cut method, the structural response method, and the Barkhausen noise technique. Finally, the experimental program supported by numerical analysis provided information about the actual state of prestressing in the bridge. Results of performed analysis suggested that the state of prestressing of the bridge in question does not significantly differ from the expected level of prestressing after 62 years of service. Subsequently, obtained conclusions enabled the determination of the load-carrying capacity for future use in the form of a pedestrian bridge.

In recent years, the technology of optical fibers has rapidly gained ground in many areas of science and industry, including the construction industry. In this article, the technology of optical fibers based on a fiber Bragg grating (FBG) was used to determine tensile forces acting in a basal reinforcement of a scaled down physical model, which included piled embankment and basal reinforcement. Installing FBG sensors on the geogrid made monitoring of axial strains possible, thus allowing determination of the behavior of the basal reinforcement of the piled embankment. On the basis of three tests performed on the physical model, numerical model calibration with the physical model was carried out using the software PLAXIS 3D Tunnel 2.4. The results showed accurate predictions, especially for the low and middle part of the measured deformations where the numerical analysis proposed a solution that can be considered as safe. Installing FBG sensors on biaxial geogrids was a bold idea that was not easy to implement. However, other possibilities have been successfully tested, such as high-frequency measurements of the response of reinforced soil structure under dynamic loading.

Headed stud shear connectors are commonly used to transfer longitudinal shear forces across the steel-concrete interface in composite structures. This paper is focused on the experimental and numerical study on the behaviour of this type of connectors. The push-out tests of headed studs, 10 mm in diameter and 50 mm in length, in normal C25/30 concrete with transverse reinforcement were carried out. The experimental study also treated the influence of the connectors spacing, in the longitudinal and transversal directions, and the thickness of the concrete slab on the shear resistance.