In recent years, concrete technology has advanced, prompting engineers and researchers to adopt advanced materials to improve strength and durability. Steel-fiber-reinforced concrete (SFRC) represents the substantial modification of concrete materials to improve their structural properties, particularly their flexural and tensile strength. Whether SFRC is stronger than conventional concrete depends on a variety of variables, including the volume, size, percentage, shape, and distribution of fibers. This article provides a comprehensive discussion of the properties of SFRC, such as durability, fire resistance, and impact resistance or blast loading, as well as the application of SFRC in structural members including beams, columns, slabs, and walls. The application of steel fibers in various types of concrete, including pre-stressed, pre-cast, self-compacting, and geopolymer concrete, was also examined in this comparative analysis review, and recommendations for the future scope of SFRC were identified.

Taking into account the requirements to reduce the release of harmful emissions into the environment, the EU’s environmental standards when transitioning to the Euro 7 standard in 2025 will actually lead vehicles having to operate without producing emissions in all driving situations. Carmakers believe that the new, much stricter regulations will mark the end of the internal combustion engine era. For example, in 2030, the manufacturer SEAT will cease its activities, leaving behind the Cupra brand, which will be exclusively electric in the future. This trend will apply not only to private vehicles (passenger cars), but also to utility vehicles, which is the subject of our research, namely the spatial tubular frame in the Bogdan ERCV27 garbage truck, presented in the form of a solid model. The peculiarity of the studied model is the installation of a battery block behind the driver’s cabin, causing an additional load to be placed on the spatial frame of the garbage truck, which in terms of its architecture is more like the body of a bus. During the conditions involving various modes of operation of a full-scale Bogdan ERCV27 garbage truck sample, questions about the strength and uniformity of its load-bearing spatial frame inevitably arise, which are decisive, even at the stage of designing and preparing the technical documentation. The main static load mode, which, despite its name, also covers dynamic conditions, was modeled using the appropriate coefficient k_d = 2.0. The maximum stresses on the model during the “bending” mode were 381.13 MPa before structure optimization and 270.5 MPa as a result of the improvement measures. The spatial frame mass was reduced by 4.13%. During the “torsion” mode, the maximum deformation values were 12.1–14.5 mm, which guarantees the normal operation of the aggregates and units of the truck.

This article investigates the degradation of stiffness in high and standard-strength concrete due to the influence of repeated loading and considers the non-linear behavior arising from localized or natural defects of concrete. The article also refers to the models from existing literature that evaluate the characteristics of concrete by enhancing its physicochemical properties through the application of natural and synthetic fibers. The impact of the service load, which influences the change in concrete stiffness, is illustrated using the elastic–plastic concrete model. The elastic–plastic model of concrete, combined with experimentally determined data such as elastic and residual deformations, simplifies the analysis of concrete beams or surface elements. This model enables static solutions of inelastic materials based on the classical theory of elasticity. The degradation of element stiffness in this model is described by the local increment of the rotation angle. Based on the model we can assume a constant stiffness along the length of the beam before as well as after exceeding the value of the cracking moment. In the case of cyclic loads, it can be assumed that residual deformations have the greatest influence on the displacement values, which in the calculation model are described by the component of the angle of rotation in the crack, describing permanent displacements.

In the mechanics of concrete constructions, one distinguishes between residual and elastic strains. Cyclic loadings evoke changes mainly in the elastic strains; however, the total strains are decided by the sum of the residual and elastic strains. The knowledge of the ratio between the residual and total strains allows to predict the total deformations of a construction assuming it is made from an ideally elastic material. This paper presents the effect of the load level at the values of the residual strains for beams made of high-strength concretes and subjected to bending. The investigations showed that the share of residual strains for these concretes differed from the share of residual strains for concretes of lower classes. The investigations were made for cyclically loaded concrete samples and ferroconcrete beams for various relative load levels. The ratio between the residual and total strains was presented in the form of a dependence on the relative load level of the element. An important conclusion was that, after the crack formation, the share of residual stresses reduced, along with the increase in the concrete strength and elastic features of the construction which started to predominate.

The aim of our work was to investigate how electric guitar strings wear out. There are many myths about string wear. We decided to investigate what the wear process looks like in real life. In our work, sound processing methods such as DTFT and spectrogram were used. However, the most important research method is the use of time-frequency analysis to study the sound of the string and its wear process. Another key method used in our work is the application of a phenomenon known from psychoacoustics, pitch. In our work, we have been able to show that the use of pitch in combination with time-frequency analysis makes it possible to demonstrate string wear. This was not achievable for previously known methods. We have also shown that the string yield limit is exceeded immediately when the strings are placed on the guitar neck. This affects the sound equation of the string. In this work, we have proposed a transformation of the classical string equation so that it correctly describes the sound of the string as it is worn. The research method we have developed, combining pitch and time-frequency analysis, could presumably be used in the future to study the wear and tear of other vibrating systems, such as bridges and viaducts.

Na podstawie badań doświadczalnych wykonanychna belkach w skali półnaturalnej z betonu o wysokiej wytrzymałościpokazano, jak stopień zbrojenia i średnica stalowychprętów zbrojeniowych wpływają na wartości rezydualnych ugięćbelek przy jej cyklicznych obciążeniach. Badania przeprowadzonona 4 seriach belek, w których na poszczególnych poziomachobciążenia pomierzono ugięcia całkowite i pozostające w zależnościod poziomu wytężenia belki. Wyniki pokazano w postacistosunku ugięć resztkowych do całkowitych w zależności od wartościobciążenia. Zmiana stosunku deformacji dla każdego zestawubelek jest analizowana pod kątem wymuszających cykli obciążeńna podstawie założeń sprężysto-plastycznego modelubetonu. Artykuł przedstawia również analizę dotychczasowychwyników badań opisanych w literaturze oraz wniosków autorów,które mają na celu ulepszenie współpracy betonu i stali dla betonówo wysokiej wytrzymałości