20.500.12556/RUP-22120 Size effect on bending strength and failure modes of finger-jointed timber Finger-jointed timber boards for cross-laminated timber production are typically assigned the same characteristic bending strength (fm,j,k) if produced from the same strength class, regardless of differences in their cross-sectional dimensions. To validate the relevance of this approach, this study investigated the effects of cross-sectional dimensions on the bending performance of finger-jointed timber produced from spruce (strength class: C24). A large industrial dataset of 1100 specimens, with seven thicknesses (ranging 20 to 40 mm) and variable widths, were statistically analyzed. The bending tests were performed with a constant span-to-depth ratio (l/h = 18), meaning thinner specimens had a shorter test span. Bending strength was modeled with Bayesian multilevel linear model, and the proportions of three quality-control failure modes (joint interface failure, joint base failure, and outside-joint failure) were analyzed with a zero-one-inflated Dirichlet regression. Based on the results, all groups with n ≥ 100 exceeded the declared fm,j,k of 27.6 MPa, with characteristic strengths of 43.7 MPa (+58.3 %), 40.0 MPa (+45.0 %), and 38.3 MPa (+38.8 %) for the 20-, 30-, and 40-mm thickness groups, respectively. Thinner specimens demonstrated higher bending strength with convincing evidence (pairwise contrasts PD = 100 % with 95 % HDPIs entirely below zero), while width had no credible effect (PD < 95 %). Dirichlet regression revealed shifts in failure mode proportions with varying strength. Higher bending strengths were associated with a higher proportion of joint interface failure. Outside‑joint failure was observed with a higher proportion in lower-strength and thicker specimens. Overall, assigning uniform fm,j,k to various cross-sectional dimensions proved to give adequate safety margins. Beyond the uniform fm,j,k, however, statistical evidence of a size effect on both bending strength and failure modes was observed. The magnitude of the observed size effect reflects the combined influence of increasing thickness and test span under the current quality control bending test regime, which means a coupled change in stressed volume and geometry rather than a pure cross-section scaling effect. These findings are relevant to flatwise four-point bending tests on finger-jointed boards from industrial production made with visually graded C24 spruce with thickness ranging 20 to 40 mm. wood finger joint strength les zobati spoj trdnost true false true Angleški jezik Slovenski jezik Članek v reviji 2025-11-18 11:02:33 2025-11-18 11:02:35 2025-11-22 03:02:49 0000-00-00 00:00:00 2025 0 0 str. 1-12 [article no.] ǂ108208 Vol. 28 Dec. 2025 0000-00-00 Zaloznikova NiDoloceno NiDoloceno 0000-00-00 0000-00-00 2025-11-13 694 2590-1230 10.1016/j.rineng.2025.108208 257590275 RAZ_Derikvand_Mohammad_2025.pdf RAZ_Derikvand_Mohammad_2025.pdf 1 0312FAC6805DDEEB6C66C898CC035691 b3dc8a15596a44d3a647145f7ec9ada295b46f20feb0b4ffa74013b1a0613305 27d5b63d-c466-11f0-8f0b-005056ac49c0 https://repozitorij.upr.si/Dokument.php?lang=slv&id=32076 https://www.sciencedirect.com/science/article/pii/S2590123025042549?via%3Dihub 1 f2f13502-c465-11f0-8f0b-005056ac49c0 https://repozitorij.upr.si/Dokument.php?lang=slv&id=32075 Inštitut Andrej Marušič Fakulteta za matematiko, naravoslovje in informacijske tehnologije 0 0 0