PSI - Issue 81

Victor Datsiuk et al. / Procedia Structural Integrity 81 (2026) 73–77

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Fig. 2. Failure mode of an experimental timber beam

An analysis of the observed damage indicates that the failure process developed gradually and was accompanied by the formation of local folds, followed by a loss of structural integrity of the timber in the critical cross-section. The recorded failure characteristics make it possible to assess the influence of long-term service and operational moisture on the mechanical behaviour of bending elements and confirm the established patterns of bearing capacity degradation of timber beams subjected to short-term loading (Fig. 2). 4. Conclusions 1. Full-scale experimental tests have demonstrated that the long-term service of pine bending beams in roof rafter structures leads to a slight reduction in their bearing capacity. 2. A clear relationship between the ultimate bearing capacity of the beams and their service life was identified. At a timber moisture content of 12%, increasing the service life from 25 to 75 years results in an approximately 9% reduction in ultimate bearing capacity, whereas at a moisture content of 15% the corresponding decrease reaches about 17%. 3. An increase in operational moisture content from 12% to 15% has a negative effect on the bearing capacity of pine beams for all investigated age groups. 4. The obtained results indicate that the influence of the temperature-humidity regime on the loss of bearing capacity is more significant than the effect of service duration alone. 5. The failure mode of the beams after long-term service was gradual and was accompanied by the development of local folds and a loss of structural integrity in the critical cross-section. 6. The results obtained provide a scientific basis for assessing the technical condition and predicting the residual service life of timber bending elements in service, as well as for substantiating decisions regarding their strengthening or replacement. Aleksiievets, V., Gomon, S., Aleksiievets, I., Homon, S., Ivaniuk, A., Zadorozhnikova, I., Bandura, I., 2024. Influence of thicknesses of outer and middle elements on the performance of nail connections. Procedia Structural Integrity 59, 710-717. Andor, K., Bellovics, B., 2020. Analysis of modulus of elasticity of spruce beams under bending with and without fibre reinforcement. Wood research 65(1), 101 110. Anshari, B., Guan, Z. W., Wang, Q. Y., 2017. Modelling of Glulam beams pre-stressed by compressed wood. Composite Structures 165, 160 – 170. Bader, M., Nemeth, R., 2018. The effect of the relaxation time on the mechanical properties on longitudinally compressed wood. Wood research 63(3), 383-398. Betts, S. C., Miller, T. H., Cupta, R., 2010. Location of the neutral axis in wood beams: A preliminary study. Wood Material Science and Engineering 5 (3-4), 173 180 BulaE,uSr.opaneadnPJeoluerknha,lAo.f, E2n0t2e3r.prCiosme Tpeacrhinngoltohgeieesff5ic(7ie-n1c2y5)o,f1s4trengthening timber beams reinforced with carbon composite rods and plates. Eastern- – 22. Datsiuk, V., Homon, S., Gomon, S., Dovbenko, V., Petrenko, O., Parfentyeva, I., Romaniuk, M., 2024. Effect of long-term operation on the strength properties of pine wood. Procedia Structural Integrity 59, 583-587. DBN B.2.6-161, 2017. Constructions of houses and buildings. Wooden constructions. Main provisions. Kyiv: Ukrarchbudinform. Diza Lestari, A. S. R., Hadi, Y. S., Hermawan, D., Santoso, A., 2018: Physical and mechanical properties of glued laminated lumber of pine (Pinus merkusii) and jabon (Anthocephalus cadamba). Journal of the Korean Wood Science and Technology 46 (2), 143-148. References