Jarosław Michałek

The durability of prestressed spun-cast concrete poles is typically assessed on the basis of the nominal mix design parameters and the assumption of material homogeneity. However, the centrifugal spinning of fresh concrete mix results in an uneven distribution of its components throughout the wall thickness, which may affect the actual cement content in individual layers and consequently, the durability. As part of this study, the distribution of cement content in spun concrete poles was analysed using an experimental approach based on the analysis of hardened concrete composition. Samples were taken from various locations along the height of the pole and divided into layers across wall thickness. Cement content, aggregate distribution, porosity, and water absorption were determined using a combination of chemical and physical methods. The results indicate that although the average cement content meets the design requirements (minimum amount of cement exceeds 300 kg/m³), there are significant local variations, particularly in the inner and outer layers of the cross section. The inner layer is characterized by increased cement content and porosity, while the outer layer is characterized by a higher coarse aggregate content and reduced cement content. It was also observed that the spinning program used in the production of the poles resulted in a homogeneous concrete structure at the top of the pole, where the spinning radius is smallest, with no signs of delamination. However, delamination of the concrete structure was observed at lower sections of the pole. These results highlight the limitations of assuming homogeneous material properties in durability design and suggest that the actual performance of spun concrete elements may deviate from predictions based on the standards. The results have direct implications for assessing the durability of spun concrete poles used in exposure classes such as XC4 and XD1.

Steel and prestressed concrete traction poles can be fixed to reinforced concrete pile foundations using typical bolted connections. The stainless steel fastening screw is connected to the ordinary steel foundation pile reinforcement by friction welding under specific friction welding process parameters. From the perspective of the structural strength of the connection between the traction pole and the foundation pile, regarding the transfer of tensile and shear forces through a single anchor bolt, the yield strength of stainless steel bolts should be R_e,min ≥ 345 MPa for M30 anchors, R_e,min ≥ 310 MPa for M36 anchors and R_e,min ≥ 300 MPa for M42 anchors. This requirement is reliably met by martensitic stainless steels, while other stainless steels have yield strengths below the required minimum. What truly determines the foundation pile’s load capacity is not the satisfactory mechanical strength of the stainless steel (here, the parameters are met), but the quality of the friction-welded end connection between the reinforcement and the threaded bars. Incorrect selection of the type of prestressing steel in the analyzed connection can have enormous consequences for foundation pile manufacturers. Annual production of foundation piles amounts to thousands of units, and an incorrect decision made by the pile designer at the design stage can result in significant financial losses and a high risk to human life. This article presents the results of studies on friction-welded connections of M30, M36, and M42 threaded bars made of austenitic 1.4301 (AISI 304) and martensitic 1.4021 (AISI 420) stainless steel with B500SP reinforcement bars. The tests yielded negative results for 1.4021 (AISI 420) steel, despite its yield strength exceeding R_e ≥ 360 MPa.

18 grudnia 2024 roku zostało opublikowane w Dzienniku Urzędowym Unii Europejskiej Rozporządzenie Parlamentu Europejskiego i Rady (UE) 2024/3110, które ustanawia zharmonizowane zasady dotyczące wprowadzania do obrotu wyrobów budowlanych na terenie Unii Europejskiej. Rozporządzenie 2024/3110 weszło w życie w zakresie kluczowych wymagań od dnia 7 stycznia 2025 roku (w pełnym brzmieniu stosowane będzie od dnia 8 stycznia 2026 r. poza art.92, który będzie stosowany dopiero od dnia 8 stycznia 2027 r.) i zastępuje wcześniejsze przepisy zawarte w Rozporządzeniu 305/2011. Rozporządzenie 2024/3110 na nowo reguluje: wymagania związane z oznakowaniem CE; zasady sporządzania deklaracji właściwości użytkowych i zgodności z uwzględnieniem zasadniczych charakterystyk środowiskowych, zasady opracowywania dokumentacji technicznej i towarzyszącej dla wyrobów budowlanych. Wprowadza nowe definicje, nowe wymagania dotyczące obiektów budowlanych związane z ich wpływem na środowisko zewnętrzne, rozszerza system oceny i weryfikacji, który łączy rygorystyczną ocenę techniczną z kompleksową analizą środowiskową, a także określa zasady funkcjonowania cyfrowego paszportu dla wyrobu budowlanego. Rozporządzenie 2024/3110 wytycza kierunek zmian na rynku wyrobów budowlanych w zakresie przede wszystkim dwóch obszarów, tj. cyfryzacji oraz zrównoważenia środowiskowego

Geological surveys provide important information for many sectors, from construction project planning to mineral exploration and environmental protection. The seismic cone penetration test with pore water pressure measurement (SCPTu) is a truly valuable tool in geological surveys. It provides detailed information on the subsurface conditions and geological characteristics of the area. The manuscript describes the methodology used to characterize the geological layers at the construction site and quantify the characteristics obtained from SCPT probing. The aim of the scientific study was to identify soft layers in the subsoil and to focus on the impact of pile driving technology on the foundation environment and SCPT probing results. The driving technology involved the implementation of 4.0 m long pyramidal precast concrete piles with pile head dimensions of 0.5 × 0.5 m and tip dimensions of 0.12 × 0.12 m. Probing of the SCPT before and after driving showed that the pile driving led to a significant increase in the velocity of shear waves in the soil at a distance of 0.5 m from the edge of the pile head, which was also reflected in the evaluation of the shear modulus G_max derived directly from shear wave velocity.

For several years now, fruit-growers have increasingly often used pre-tensioned, pre-stressed concrete posts for supporting branches of fruit trees and suspending protective nets in order to limit damage to fruits caused by hail, wind, snow, heavy rainfall, insects and birds. Pre-tensioned, pre-stressed concrete posts most often have a trapezoidal cross-section, which is ideally suitable for mass production in a self-supporting non-dismantlable steel mould on a pre-stressing bed. Posts with 70 mm × 75 mm, 80 mm × 85 mm and 90 mm × 95 mm cross-sections are typically produced, whereas 100 mm × 120 mm and 130 mm × 140 mm posts are manufactured to order. Furthermore, it is proposed to produce hollow posts. Such posts are lighter than solid posts, but they require a more complicated production technology. This paper presents selected parts of a comparative computational–experimental analysis of solid and hollow posts. In the Building Structures Laboratory in the Building Structures Department at the Civil Engineering Faculty of the Wrocław University of Science and Technology, experimental tests of pre-stressed concrete orchard posts of 70 mm × 75 mm and 90 mm × 95 mm with solid and hollow cross-sections were carried out on a full scale. The theoretical analysis and research has shown that the resistance to bending, cracking resistance and rigidity of hollow posts (with their cross-sectional outline unchanged) will not significantly differ from those of the currently produced solid posts. At same time, material savings will be achieved. Therefore, the main task is to master the continuous moulding of hollow posts from dense plastic concrete with the simultaneous pulling out of the cores, producing longitudinal hollows in the posts.

Przedmiotem artykułu są wyniki badań laboratoryjnychw skali naturalnej elementów nawierzchni przejazdu kolejowo-drogowego. Nawierzchnia analizowanego przejazdu kolejowo-drogowego składa się z wewnętrznych i zewnętrznychmałogabarytowych płyt żelbetowych oraz belek podporowych.Płyty wewnętrzne opierają się obustronnie na stopkach szyn poprzezwewnętrzne amortyzatory polimerowe, które redukują oddziaływaniadynamiczne kół samochodów i stabilizują płyty w kierunkuprostopadłym do szyny. Natomiast płyty zewnętrzne z jednejstrony opierają się na stopce szyny za pośrednictwem polimerowychamortyzatorów zewnętrznych, a z drugiej na pasie gumowymułożonym na żelbetowej belce podporowej, która może stanowićjednocześnie krawężnik. Elementy nawierzchni przejazduzaprojektowano na maksymalny nacisk koła samochodu S o wartościcharakterystycznej Pk = 60,0 kN. Badania laboratoryjne zrealizowanow laboratorium Katedry Konstrukcji Budowlanych na WydzialeBudownictwa Lądowego i Wodnego Politechniki Wrocławskiej.Program badań obejmował sprawdzenie zarysowania i ugięcia oraznośności granicznej na zginanie wewnętrznej płyty przejazdowej.Badania płyt przejazdowych na zginanie potwierdziły ich właściwąnośność w stanie eksploatacyjnym i granicznym oraz możliwośćich stosowania na liniach kolejowych i tramwajowych.

This paper describes a study of the chloride content in the concrete lagging of prestressed concrete elements of the roof structure of an aluminium foundry building. Sources of chloride pollution in industrial facilities are discussed. Methods for collecting dust deposited on the structure and sampling concrete for chloride concentration testing are presented in detail. The test methods used and the apparatus used to assess the chloride content at the thickness of concrete reinforcement lagging are presented. Investigations of the chloride content in the concrete of the reinforcement cover showed a very high concentration of chloride in the near-surface layer, depending on the location of the element in relation to the source of chloride emission into the environment. In contrast, the concrete of the deeper layers of the lagging contained very small amounts of Cl⁻ chlorides. The results of the chloride content of the lagging concrete were plotted against the distance from the surface of the specimen and approximated by the function C(x,t) based on Fick’s second law and its solution. A satisfactory fit of the course of this function to the experimental results was obtained. Based on the obtained C(x,t) function, the durability of the main structural components of an aluminium foundry industrial hall operating in a chloride environment was estimated.

W artykule przedstawiono stan techniczny elektroenergetycznych żerdzi z betonu wirowanego po ponad trzydziestoletniej eksploatacji. Słupy te są jednymi z pierwszych wytworzonych w Polsce w technologii betonu wirowanego na laboratoryjnej linii produkcyjnej zlokalizowanej na terenie Politechniki Wrocławskiej. Na fotografiach przedstawiono istniejące uszkodzenia żerdzi, omówiono je oraz wskazano potencjalne przyczyny

Small wind turbines (SWT) generate electricity up to several dozen kilowatts. They can be divided into turbines with a horizontal axis of rotation (Horizontal Axis Wind Turbines) and turbines with a vertical axis (Vertical Axis Wind Turbines).The paper discusses design issues related to various types of wind turbines, and lays down general principles for the selection of support structures for small wind turbines (SWT) with a horizontal axis of rotation. The possibilities of using E-type spun prestressed-concrete poles used in medium voltage overhead power lines as SWT supporting structures are presented and discussed with regard to technical benefits of their application.