Krzysztof Robert Czech

This paper attempts a probabilistic analysis of the load-bearing capacity of adhesive anchor connections, taking into account the variability of embedment depth, concrete grade, and resin properties. It is a method for assessing the strength of the steel anchor, epoxy resin, and concrete, considering material and installation uncertainties. Previous experimental studies have shown differences in the load-bearing capacity of adhesive anchors depending on embedment depth and concrete grade. The probabilistic approach involves treating material, geometric, and installation parameters as random variables.

Numerical simulations, unlike experimental studies, eliminate material and setup costs while significantly reducing testing time. In this study, a random distribution program for steel-recycled polyethylene terephthalate hybrid fiber recycled concrete (SRPRAC) was developed in Python (3.11), enabling direct generation in Abaqus. Mesoscopic simulation parameters were calibrated through debugging and sensitivity analysis. The simulations examined the compressive failure mode of SRPRAC and the influence of different factors. Results indicate that larger recycled coarse aggregate particle sizes intensify tensile and compressive damage in the interfacial transition zone between the coarse aggregate and mortar. Loading rate strongly affects outcomes, while smaller mesh sizes yield more stable results. Stronger boundary constraints at the top and bottom surfaces lead to higher peak stress, peak strain, and residual stress. Failure was mainly distributed within the specimen, forming a distinct X-shaped damage zone. Increasing fiber content reduced the equivalent plastic strain area above the compressive failure threshold, though the effect diminished beyond 1% total fiber volume. During initial loading, steel fibers carried higher tensile stresses, whereas recycled polyethylene terephthalate fibers (rPETF) contributed less. After peak load, tensile stress in rPETF increased significantly, complementing the gradual stress increase in steel fibers. The mesoscopic model effectively captured the stress–strain damage behavior of SRPRAC under compression.

This paper analyzes the seismic performance and damage characteristics of high-rise frame-core-tube structures on soft soil, explicitly incorporating dynamic soil–pile–structure interaction (SSI). A refined 3D finite element model of a 52-storey soil–pile–structure system was developed in ABAQUS, utilizing viscous-spring boundaries and the equivalent nodal force method for seismic input. Nonlinear analyses under six seismic waves were compared to a fixed-base model neglecting SSI. Key findings demonstrate that SSI significantly alters structural response; it amplifies lateral displacements and inter-storey drift ratios throughout the structure, particularly at the top level. While total base shear decreased, frame column base shear forces substantially increased. SSI also reduced peak top-storey accelerations, diminished short-period spectral components, and prolonged the predominant period of response spectra. Analysis of member damage revealed SSI generally reduced compressive and tensile damage in core walls, floor slabs, and frame beams. Principal compressive stresses at the base of frame columns increased under SSI. These results highlight the necessity of including dynamic SSI in seismic analysis for high-rises on soft soil, specifically due to its detrimental amplification of forces in frame columns.

The manuscript reviews the methods and mathematical relationships for estimating the theoretical load capacity of steel anchors – both single-anchor (bonded perpendicularly and diagonally to the surface) and multi-anchor systems. Input data for comparative analyses (experimental load capacity of anchors) were obtained from laboratory tests. A total of 62 R-STUDS bonded anchors, made from metric studding M12 threaded rods, made of carbon steel class 5.8, were tested. The scope of the tests included: 22 single anchors bonded at an angle of 90° to the concrete surface, 12 single diagonal anchors (4 anchors at 30°, 45° and 60° each), 16 anchors in twin-anchor systems at 30° and 45° angles, and 12 anchors in three-anchor systems (2 diagonal anchors at an angle of 60° and one at an angle of 90°). Laboratory tests, with the use of the HYSDOZOK hydraulic load-setting system, were carried out at Bialystok University of Technology in three stages. Comparison of the actual anchor load capacities (experimental load capacities) with the corresponding theoretical load capacities in each of the tested anchor groups showed very large discrepancies in the results (from -97.2% to +139.5%). Most of the results obtained indicate higher values of theoretical anchor load capacity (Pult) than experimental load capacity (Pexp). Further work on adjusting the mathematical relationships used to estimate the load capacity of steel anchors was needed. However, due to limitations in the size of the current manuscript, the results of work related to the application of heuristic algorithms to optimize the mathematical models will be presented in the authors' next publication.

This paper presents an overview of representative up-to-date research and the authors’ own experimental results from tests of wall elements and a horizontally loaded timber-framed modular building. The research has been conducted in connection with the development of timber-based structures in recent years. In the present research, wall elements and modules of timber-frame construction with life-size dimensions were used. So far, these types of structures have mainly been tested in laboratories—especially with regard to anchoring and cyclic loading. An experimental testing was carried out on a natural scale in two stages based on the standard procedure described in EN 594. In the first stage, wall panels were tested. In the second stage, tests were carried out on a complete four-storey building. Dowel fasteners were used to fix the sheathing to the load-bearing wall structures. Additionally, the sheathing was glued to the timber frame of the walls. The same type of wall element was used for the construction of the tested building. Horizontal loads were applied at the height of the top of the walls in both stages. The building loads were applied in a direction perpendicular to the longitudinal axis of the modules. Based on test data, the stiffnesses of the wall panels and the whole building were derived, as well as the type of interaction between the modules and the influence of the walls on the spatial work of the building. On the basis of the conducted studies, both the stiffness of the walls in different configurations and the stiffness of the complete building were determined, as well as the nature of the interaction of neighbouring modules and the influence of wall connections on the 3D working of the building. The results show that the stiffness of the building in the horizontal plane in the direction of the applied load is almost twice as high as the sum of the stiffnesses of the building walls in the same direction.

Glass fiber-reinforced polymer (GFRP) utility poles are becoming more widespread in European countries. To ensure the integrity and safety of poles, it is necessary to carefully examine their structural features. The purpose of this paper is to present the numerical model of a column made with the engineering simulation software ANSYS and to compare the experimentally determined values of the stresses that lead to column failure close to the inspection hole with the results obtained using the numerical model. The critical buckling and failure loads for GFRP poles, as well as the associated modes of failure, were correctly predicted by the finite element method used in this study. Failure occurred in the middle of the inspection hole’s longer edge at a stress level of 220–250 MPa. A comparison of the stress using the ANSYS simulation software that led to the destruction of the column with those measured experimentally using strain gauges revealed a good agreement between their values.

The work concerns the influence of the method of numerical modelling of the connections of the roof truss and vaults with the walls of historic masonry objects structures on the local stress distribution in the walls. At the outset, the need to search for rational modelling was justified due to the large size of the calculation models and the erroneous results obtained with oversimplification of the model. Four methods of modelling the connections between the walls and roof truss and vaults were analysed. The first method was to describe the elements of walls and foundations as solid elements, the ribs of the vaults and the roof truss as beam elements, and the vaulting webs as shell elements. The remaining methods 2–4 describe the walls as shell elements. In places where the walls join with the roof truss and vaults, fictitious/fictional elements in the form of rigid horizontally-oriented shells were used in model No. 2. In model No. 3, fictitious rigid horizontally-oriented shell elements in addition to local rigid vertically-oriented shells were used, while in model No. 4, only fictitious rigid vertically-oriented shell elements with stepwise decreasing protrusions were introduced. The best solution in terms of local stress distribution turned out to be the description of connections with fictitious shell elements in the case of model No. 4. This approach slightly increases the number of unknowns, and makes the results of stresses in the connection areas realistic in relation to full modelling with solid finite elements.

Compounds with lower dynamic stiffness are a better solution from the tyre/road noise point of view. The article presents the constructed test stand for the evaluation of dynamic stiffness both in in situ and in laboratory conditions. As a result of the tests, it was found that poroelastic pavements have a much lower dynamic stiffness (from 138.3 to 143.0 dB re. 1 N/m) compared to the asphalt concrete pavement (150.3 dB re. 1 N/m). In the group of poroelastic pavements, lower dynamic stiffness is characteristic for pavements with a binder course of porous asphalt. The results of the research are a contribution to further work on the influence of the dynamic stiffness of the pavements on the tyre/road noise level. The conducted measurements and analysis of the results prove the usefulness of the proposed test stand for determining the dynamic stiffness of bituminous mixtures in laboratory and field conditions. This is confirmed by the coherence between the force and acceleration signals at the level of at least 0.96—which indicates a very good validation of the test results with a random error lower than ±5% with 90% confidence level.

In predicting the impact of vibrations propagated in a ground on newly designed construction objects, it is extremely important to reliably measure the time histories of velocity or acceleration at the site of the planned investment. As some studies show, the method of coupling accelerometers and geophones to the ground can affect not only the level of peak particle accelerations (PPA) or peak particle velocities (PPV)—commonly used in this type of evaluation—but also vibration frequency distribution of recorded signals. This makes it difficult to compare and analyze the results obtained by various research teams. Conclusions based on this type of comparison may be wrong. For this reason, it is extremely important that reliable dynamic measurements related to the propagation of ground surface vibrations should be carried out using not only appropriately selected measuring equipment (with the required sensitivity and measurement ranges—both in the time domain and frequency domain), but also the measurement bases/setups used for mounting various types of transducers, whose natural frequencies will be outside the frequency range relevant to the possible impact of vibrations on buildings and human beings inside. The paper presents the results of modal analyses carried out with the use of Ansys Engineering Simulation and 3D Design Software (based on the Finite Element Method) for three different types of measuring bases used to coupling accelerometers to the ground. Measuring bases selected for numerical analyses were in the form of a stiff steel spike of an X-shaped cross section (a measuring base No. 1) and two steel spikes of L-shaped cross-sections (a measuring bases No. 2 and No. 3). In the places of screwed accelerometers (three different types of IEPE/ICP transducers of varying sensitivity and a weight) point masses were attached to the measuring bases. As a result of the analyses, it was possible to determine the impact of individual methods of coupling of accelerometers to the ground on the reliability of recorded ground surface accelerations. Among others it was concluded that in each analyzed case the lowest natural frequencies of the measuring bases with attached accelerometers significantly exceeded 100 Hz. The widest frequency band free of resonance vibrations can be provided by the measuring base No. 3 (L50 × 50 × 5).