Arkadiusz Denisiewicz

W artykule przedstawiono wyniki badań belek dwuteowych z drewna, w których analizowano wpływ wadliwych połączeń klinowych w pasach dolnych na ich nośność i sztywność. Pasy wykonano z drewna sosnowego klasy C24 łączonego na mikrowczepy, a środnik z płyty OSB. Próby zginania czteropunktowego przeprowadzono na belkach o długości 540 cm, w których złącza umieszczono w strefie maksymalnych momentów zginających. Wady obejmowały brak pełnego sklejenia, przesunięcie profilu oraz rozwarstwienie w strefie styku. Stwierdzono, że wadliwe połączenia obniżają sztywność giętną o około 12% i nośność o 15–20% w porównaniu z belkami bez wad. Pęknięcia inicjowały się w strefie rozciąganej, prowadząc do gwałtownej utraty nośności. Wnioski wskazują na konieczność unikania lokalizacji złączy w strefach rozciąganych oraz kontroli jakości procesu klejenia. Wyniki badań potwierdzają kluczową rolę jakości połączeń klinowych dla niezawodności belek dwuteowych i stanowią podstawę dalszych analiz optymalizacyjnych.

The article presents the results of comparative studies of I-beams and laminated beams made of OSB boards, aimed at demonstrating the impact of flange joint defects in I-beams on their load-bearing capacity and at presenting an alternative structural solution. As part of the experimental research, destructive bending tests were carried out on beams with a span of 540 cm and a cross-sectional height of 30 cm, in accordance with EOTA guidelines. The results revealed a significant sensitivity of I-beams to the presence of material defects in the flanges. In contrast, the double-glued laminated beams, despite their slightly lower stiffness, achieved substantially higher load-bearing capacities as well as more repeatable and predictable behavior. The analysis showed that OSB laminated beams can be a viable alternative to I-beams in applications where greater reliability is required.

The paper focuses on problems of the rheology of wooden beams. The main aim of the theoretical and experimental research was to select a linear viscoelastic rheological model best describing the behavior of wooden beams. The experimental elements were full-size beams made of pine wood. The beams were subjected to a long-term multistage loading program. Simple models of linear viscoelastic materials, i.e., the three-parameter standard model and the four-parameter Burgers’ model, reveal essential restrictions and are too poor to describe processes of wood creeping, particularly in the initial period of the phenomenon, as well as in the case of multistage loads. Our research has shown that, under constant heat and moisture conditions, the five-parameter rheological model is sufficient to describe wood creep under constant loading. In contrast, the model deviates significantly from experimental results in the case of a multistage loading program. In view of this, a six-parameter rheological model was used, which fits the experimental data perfectly. Thus, the decisive verification of the assumed rheological model can be ensured only by carrying out experiments with the use of a multistage program of loads (clear separation of the identification of the model’s parameters from its verification).

The study presents experimental and numerical analyses comparing two types of wood-based structural beams—laminated beams made of oriented strand board (OSB) and traditional wooden I-beams. Load-bearing capacity, stiffness, and susceptibility to loss of stability were compared. Full-scale four-point bending tests were conducted on 5400 mm-long beams with 300 mm cross-sectional height, in accordance with the European Organisation for Technical Approvals (EOTA) guidelines. The results showed that OSB laminated beams, despite having about 20% lower bending stiffness, achieved up to 46% higher ultimate load capacity compared to I-beams. Failures in I-beams were mainly initiated by material defects and weaknesses in the glued joints of flanges, whereas laminated beams exhibited more uniform and predictable behaviour with greater repeatability of results. Numerical simulations performed in Abaqus/Standard 2022, including linear buckling and modal analyses, confirmed the experimental findings and indicated higher global stability and dynamic stiffness of laminated beams. The numerical model was validated in the elastic range and subsequently used to assess stability and dynamic behaviour, which are governed by linear elastic stiffness. The obtained results demonstrate that OSB laminated beams can serve as a potential alternative to conventional I-beams in structural applications requiring high safety and durability, offering a structurally efficient and more failure-tolerant configuration.

This study investigates the fatigue performance of timber joints with connector plates through experimental testing and numerical simulation. A displacement-controlled fatigue test was conducted on a timber connection composed of C24-grade wood elements and a T150 steel connector plate. Failure occurred due to progressive shearing of the plate teeth. Numerical analyses were performed using Abaqus (for static FEM simulation) and fe-safe (for fatigue prediction), applying two models: Morrow and Goodman. Simulations evaluated the effects of varying displacement amplitudes (0.5 mm, 2.5 mm, 5.0 mm), friction coefficients (0.1, 0.3, 0.5), and load frequencies (6 Hz, 10 Hz). Results show that increased displacement and friction lead to lower fatigue life due to localized stress concentrations. The predicted damage locations corresponded with experimentally observed failure zones. The applied Critical Plane methodology enabled reliable fatigue life estimation. The approach confirms the usefulness of FEM-based modeling in predicting fatigue failure in timber-steel joints and highlights key parameters affecting durability.

The article presents the results of laboratory studies on the impact of replacing part of the cement and natural aggregate with amphibolite dust and aggregate on the properties of concrete. The dust and amphibolite aggregates used in the research are by-products generated during the industrial processing of amphibolite rock. The study included a sieve analysis of the applied aggregates, the design of concrete mix formulas, determination of their consistency, as well as an examination of concrete shrinkage, assessment of specimen absorbability, and evaluation of compressive, flexural, and splitting tensile strength in accordance with relevant standards. The research results enabled an assessment of the impact of recycled amphibolite additives on the mechanical and physical properties of concrete, which is significant for optimizing concrete mix compositions.

This paper presents the results of numerical investigations focused on a structural assembly consisting of thin-walled perforated steel beams joined to a particleboard panel. The simulations were performed using the finite element method (FEM), incorporating both physical and geometric nonlinearities, along with detailed modeling of contact interactions between the beams and panel elements. The primary objective was to establish load-capacity curves for the central beam in structural systems with spans ranging from 3 to 6 m, and to identify failure modes associated with different span lengths. To verify the reliability and accuracy of the numerical approach, laboratory tests were conducted on two representative configurations with spans of 3 and 6 m. Additionally, the mechanical properties of the beam materials were evaluated using samples extracted from the tested elements. The experimental findings confirmed the numerical model’s accuracy and its suitability for analyzing structural responses across the full span range considered.

This article presents the results of numerical simulations of a structural system consisting of steel perforated thin-walled beams and a steel grating. The simulations were conducted using the finite element method. The analysis took into account physical and geometric nonlinearity as well as the contact between the steel grating and the beams. The main goal of the research was to develop load-bearing curves for the main beam in the span range of 3–6 m and to identify destruction patterns depending on the span of the structural system. For the purpose of validating the developed numerical model, laboratory tests were conducted on two structural systems with spans of 3 m and 6 m, as well as tests on the strength parameters of the material taken from the tested beams. The laboratory tests confirmed the correctness of the proposed numerical model, which allowed for the simulation of the behavior of the structural system in the full range of spans.

Polyurethane (PU) has been used in a variety of industries during the past few years due to its exceptional qualities, including strong mechanical strength, good abrasion resistance, toughness, low-temperature flexibility, etc. More specifically, PU is easily “tailored” to satisfy particular requirements. There is a lot of potential for its use in broader applications due to this structure–property link. Ordinary polyurethane items cannot satisfy people’s increased demands for comfort, quality, and novelty as living standards rise. The development of functional polyurethane has recently received tremendous commercial and academic attention as a result. In this study, the rheological behavior of a polyurethane elastomer of the PUR (rigid polyurethane) type was examined. The study’s specific goal was to examine stress relaxation for various bands of specified strains. We also suggested the use of a modified Kelvin–Voigt model to describe the stress relaxation process from the perspective of the author. For the purpose of verification, materials with two different Shore hardness ratings—80 and 90 ShA, respectively—were chosen. The outcomes made it possible to positively validate the suggested description in a variety of deformations ranging from 50% to 100%.