Structural Mechanics of Engineering Constructions and Buildings

Thermoplastic polymeric materials have found wide application as protective and antifriction coatings and interlayers of friction units. Spherical bearings include relatively thin sliding layers made of antifriction materials. Polytetrafluoroethylene (PTFE) is widely used as a material for sliding layers. However, at present, there are modern composite and modified materials with improved physical and mechanical properties that can be used as sliding layers. Antifriction materials are often modeled in terms of elasticity theory or elastoplasticity theory. However, it has been established that these materials exhibit viscoelastic properties. A series of experiments to determine the thermomechanical properties of the materials is performed in the current work. PTFE, a metal composite based on PTFE with bronze inclusions (MAK (F4BR40M2)) and structurally modified Arflon AR-200 PTFE were investigated using dynamic mechanical analysis. The temperature change range [-40; +80] °C was considered, it corresponds to the operating temperatures of bridge structures. Temperature dependencies of the storage modulus, loss modulus and loss tangent were obtained. Viscoelastic models of material behavior, such as Maxwell bodies using Prony series and temperature-time analogy, were constructed based on experimental data. Viscoelastic behavior of materials was analyzed in terms of deformation of a bridge spherical bearing under static and periodic loads, taking into account the ambient temperature. The relationships for the effect of temperature on the stress-strain response and contact parameters were obtained. The influence of the thermal expansion coefficient of materials on the structure behavior was considered. It was found that the sliding layer made of MAK allows for a more favorable stress-strain state compared to the structure including a sliding layer made of PTFE: the maximum stress intensity is less by ~ 3%; the maximum strain intensity is less by ~ 20%; displacements along the normal to the sliding layer are less by ~ 17.2%.

The paper presents a justification of the parameters of the Concrete Damage Plasticity (CDP) model used for numerical analysis of reinforced concrete structures. It is shown that the results of nonlinear simulations are highly sensitive to the choice of plasticity parameters and the adopted concrete stress-strain relationships. The aim of the study is to analyse the sensitivity of the key CDP parameters and to verify the applicability of the model under static loading conditions. Numerical simulations were performed using the finite element method in Abaqus. The influence of the dilation angle, yield surface parameters and energy-consistent stress-strain diagrams on stiffness and load-bearing capacity was investigated. The model was verified at both the material and structural levels. It is demonstrated that the use of physically justified parameters ensures an accurate reproduction of the nonlinear behaviour of reinforced concrete elements up to failure.

Timber structures, in particular glued laminated beams, have a number of advantages that contribute to their wide use in industrial and civil construction. The development and research of design solutions that utilize the strength properties of structural timber more efficiently is a key area for improving the performance of timber structures. The object of this study is a timber beam of rectangular cross-section loaded with a uniformly distributed load, the outline of which is based on the uniform-strength trajectories of beams in bending and horizontal shear. The construction of the outline of rational timber beams (RTB) was based on determining the coordinates of nodal points by constructing straight lines tangent to the contour of a beam of uniform strength. The RTB is a beam with a zone of constant rigidity in the middle of the span and undercuts in the support zones. The purpose of this approach was to create a resource-efficient beam structure made of glued timber, characterized by lower material consumption compared to beams of constant cross-section height along the entire span, as well as relative ease of manufacturing. The results of the study show that the relative values of the RTB parameters, such as: the height of the support section relative to the maximum height of the section h sup/ h , the length of the undercut relative to the span l cut/ L and the angle of the undercut acut, depend only on the ratio of the maximum height of the section to the span h / L . The change in the width of the section b and the value of the external load q have no effect on them. The theoretical savings of structural timber of grades 1 and 2 are 6.2%...18.3%.

The problem of determining the dynamic characteristics of buildings based on microseismic observations is considered. The relevance of the research is associated with regulatory requirements that necessitate the determination of actual dynamic parameters of buildings during structural inspection and monitoring. Existing approaches based on microseismic background analysis allow the identification of natural frequencies; however, they do not always provide unambiguous identification of vibration modes and their type (bending or torsional). The aim of this study is to refine the methodology for building surveys by improving the identification of vibration types and mode shapes through the comparison of experimental observations with numerical modeling results. The object of the study is the building of the Institute of Geophysics of the Ural Branch of the Russian Academy of Sciences (IG UB RAS). Ambient vibration (microtremor) recordings were performed, followed by spectral analysis of the signals to determine the natural frequencies of the building. The obtained experimental data were compared with the results of numerical modeling carried out in the SCAD software environment, taking into account the structural characteristics of the building and the geological properties of the foundation. The comparison showed good agreement between experimentally determined and calculated frequencies. It was also found that different vibration modes, including bending and torsional modes, may dominate in different parts of the building. The results demonstrate the effectiveness of a combined approach based on instrumental observations and numerical modeling for refining the dynamic characteristics of buildings and may contribute to the development of criteria for the interpretation of microseismic data and the improvement of methodologies for evaluating building dynamics.

Concrete remains the most widely used construction material, yet its brittleness and susceptibility to cracking limit its application in high-load structures such as aerodrome pavements. Improving mechanical strength and durability is therefore essential. While fiber reinforcement has been widely studied, mono-fiber systems often yield only partial benefits. Hybrid reinforcement using basalt macro fibers and microfibers presents a sustainable alternative, but remains underexplored, particularly for aerodrome pavements. This study investigated the influence of hybrid basalt fibers on the compressive strength of concrete at 7, 14, and 28 days, with the goal of identifying the most effective fiber proportion. Concrete mixes with different ratios of basalt macro fibers (A) and microfibers (B) were produced, cast into standard cubes, and tested for compressive strength following established guidelines. Results indicated that hybridization significantly improved strength development compared to the control. Fiber concrete mixture series achieved the highest 28-day compressive strength of 72.8 MPa, outperforming both mono-fiber and control samples. This confirms the synergistic role of hybrid fibers in enhancing crack control and load transfer. The findings suggest that hybrid basalt fiber reinforcement offers a practical, sustainable solution for high-performance concrete, with strong potential for application in aerodrome pavements and other demanding structural works.