PSI - Issue 59

Valentin Aleksiievets et al. / Procedia Structural Integrity 59 (2024) 710–717 Valentin Aleksiievets et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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strength (Yasniy et al. (2022); Green and Kretschmann (1992); Sobczak-Piastka et al. (2020); Gomon et al. (2023)), low density, chemical stability (Homon et al. (2023); Huang et al. (2006)), plasticity (Thygesen et al. (2010); Homon et al. (2023); Janiak et al. (2023); Madsen (1974)), and considerable durability (Zhao et al. (2020); Soriano et al. (2016); Mascia et al. (2018); Patton-Mallory and Cramer (1987); Donadon et al. (2020)).

Nomenclature a

width of the outer element width of the middle element height of the nail connection diameter of the nail 2 mm shear deformations design bending moment tensile strength of the nail flexibility coefficient initial modulus of elasticity

с h d

Δ u R k

bearing capacity of the nail connection

f h,1,k , f h,2,k stresses in wood M y,k

f u β

Е 0 ρ k

density of wood

Materials and structures made of wood are most commonly used in the construction of civil, industrial, and hydraulic engineering projects (Zhou et al. (2018); Nsouami et al. (2022); Gomon et al. (2022); Bosak et al. (2021); Pavluk et al. (2023)). In construction practice, nails, glued (Sobczak-Piastka et al. (2023); Gomon et al. (2022)) and other connections of wooden elements and structures are widely used. Nails are extensively used in modern wooden structures, nodes and junctions of multi-span trusses, rigid frame joints, and continuous beams of wooden floors. In cases with significant loads, they are designed as multi-nail connections, allowing for various design options. Consequently, there is a practical need for optimizing such connections. Research on the strength and deformation characteristics of nail connections in wooden elements under single load conditions is significant. According to current design standards, existing calculation methods do not fully account for numerous factors influencing the stress-strain state of elements (DBN B.2.6-161:2017, Eurocode 5: 2004; NDS:2018). In many cases, there is material waste, the labour-intensive manufacturing of connections, and sometimes insufficient reliability of structures. Therefore, issues related to investigating the development of the deformative state and determining the bearing capacity of nail connections in wooden structures under single-load conditions are becoming increasingly practical. This study aims to conduct theoretical and experimental research to optimize nail connections of wooden elements and provide suggestions for determining the bearing capacity of such connections. 2. Methods of experimental research The experimental research program included studying the influence of single-load conditions on the performance of nail connections in wooden structures. Samples were manufactured to investigate the behaviour of nail connections under static loads to achieve the set goal. A total of 45 samples were studied (3 nail connections for each variable geometric characteristic). Among them were 18 connections with different thicknesses of middle elements (35, 40, 42.5, 45, 47.5, 50 mm) with nail diameter 4.5 mm, 18 connections with different thicknesses of outer elements (10, 15, 20, 25, 30, 35 mm) with nail diameter 5.5 mm, and 9 connections with different nail diameters (4.0, 5.0, 5.5 mm). The sample testing was conducted with a moisture content of 12% for second-grade pine wood. During the experimental research, the change in shear deformation was recorded at each level. The samples were symmetrical nail elements made of wood with a total height of 260 mm. The number of nails