PSI - Issue 72

Sviatoslav Homon et al. / Procedia Structural Integrity 72 (2025) 301–307

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et al. (2024)). When designing products, components, and elements, it is crucial to consider various factors such as temperature (Sinha et al. (2012)), humidity (Madsen (1974); Homon et al. (2023); Thygesen et al. (2010); Janiak et al. (2006); Roshchuk et al. (2024)), aggressive environments (Homon et al. (2023)), and other significant properties (Zakic (1974); Zhao et al. (2020)) that can impact the mechanical properties of wood during its use. The utilization of glued wood enhances the range of its applications. Glued timber elements and structures are used in the design of long-span industrial and civil buildings, as well as bridges and bridge crossings (Sobczak-Piastka et al. (2023); Ansharietal.(2017); Gomon et al. (2022); Sobczak-Piastka et al. (2020)). In such cases, it is permissible to use not only first-grade wood but also material of lower grades.

Nomenclature σ с

compressive stress

relative tensile strains of glued wood along the fibers

u c

relative tensile strains of glued wood along the fibers to the end of the 1-st section tensile stress of glued wood along the fibers to the end of the 1-st section

u c1 σ с1 E 0

initial modulus of elasticity ultimate strength of glued wood

f c,0,d u c,0,d u c,el u c,pl

relative ultimate tensile strains of glued wood along the fibers elastic component of relative tensile strains of glued wood along the fibers plastic component of relative strains of glued wood along the fibers ultimate relative tensile strains of glued wood along the fibers stress of modified wood that correspond the ultimate relative strain

u c,u σ с,u

residual (final) relative strains of modified wood

u c,fin σ с,fin

stress of modified wood that correspond the residual (final) relative strains

An equally important aspect is the investigation of wood performance during the subcritical and critical stages. Understanding this process will facilitate further calculations of elements and structures through the deformation method (Gomon et al. (2022); Pavluk et al. (2024); Gomon et al. (2024)) and will significantly reduce material consumption. We have conducted both experimental and theoretical studies on solid and modified hardwood and coniferous wood, taking into account the wood's age and moisture content (Homon et al. (2023); Janiak et al.; Homon et al. (2024); Yasniy et al. (2022)). The key parameters determined include temporary ultimate strength, critical, ultimate, and residual deformations, as well as the modulus of deformation. For laminated wood, such studies are largely absent, with the notable exception of bamboo laminated wood (Zhou et al. (2018)). The objective of this article is to perform experimental and theoretical studies on glued hardwood and coniferous wood under axial compression along the fibres, utilizing short-term loading, and to establish the primary strength and deformability parameters during the subcritical and critical stages of the material's performance. 2. Methods of experimental research The following wood species were chosen for the experimental studies: larch, pine, spruce, birch, alder, and ash. In line with the current standards (DSTU 3129: 2015), we selected trees featuring straight trunks and minimal branching. This approach helped us reduce the occurrence of knots in the wood and enhance the parallelism of the fibres. Once the selected trees were felled, the trunks were transported to the carpentry workshops and processed into timber. After drying the elements in thermal chambers to achieve the average standard moisture content, the timber of all studied species was cut into boards. Subsequently, these boards were planed to a cross-section of 10x40 mm and a length of 100 cm. The planed boards were then glued together in a layer-by-layer fashion using Casco Silva resorcinol adhesive, classified as moisture resistance class D3 under EN 204/205. The plank-glued wooden beams were manufactured in the factory. To ensure strong glue joints, a specific gluing regimen was followed. The moisture content of the workpieces was maintained within specified limits 12%, and the surface roughness of the wood was not lower than class 8. The