PSI - Issue 54

Anna Karolak et al. / Procedia Structural Integrity 54 (2024) 460–467 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

466

7

presented. The beams jointed with the simple laps and inclined laps obtained the flexural load-carrying capacity values between 8 and 10 kNm, which corresponds to the ratio of 35%-40% of the solid beam capacity. The beams jointed with the the stop-splayed scarf joint that were created in the horizontal plane obtained the flexural load-carrying capacity level of 7 kNm, which corresponds to the ratio of around 30% of the solid beam capacity. The beams with stop-splayed scarf joint created in the vertical plane obtained the values of the flexural load-carrying capacity higher than 8 kNm, which corresponds to the ratio of around 35% of the solid beam capacity. On the basis of the failure images of the tested joints, the identifying of the regions of the highest stress, is possible, along with the description of the failure modes characteristic for the joints. Generally, a significant loosening of the joints, and cracking at some specific points and in some specific areas was observed, in the result of the increasing loading. The joints in the beams were working asymmetrically. In the case of the simple lap or the inclined lap joints strengthened with 4 metal bolts applied, failure was in result of cracking of the beam in the tensile zone, at the level of the lower connectors. What is more, cracks that were a result of the deformation of the joint and the compression of one part against the other part were noticed. Similar phenomenon was observed in the case of the inclined lap joint with 2 metal bolts applied, however, the breakage was observed in the middle height, at the level of the connectors and also below, in the tensile zone. The applied strengthening elements in the stop-splayed scarf joints in the horizontal more or less prevent loosening of the joint, nevertheless, in each case, significant loosening of the joint at the failure occurred. The cracks appeared in the result of compression of the one part of the joint – the upper part, against the other – the lower part, at the edges of the joint. These were the areas of the stress concentration. In turn, the failure of the stop-splayed scarf joint in the vertical plane was similar to the failure mechanism of the beams with the laps in the vertical plane. This was due to breakage – delamination of the fibres in the lower part of the beam, that was under tension, and also due to excessive compression of one part of the joint against the other part pf the joint. In this case cracks appeared at the level of the upper connectors. Additionally, in all beams, the occurring cracks were noticed in the areas and at the points of the material discontinuity, e.g. at the holes for the applied connectors or in the places where the natural wood defects (like knots or precracks) existed. These regions were sometimes the weakest, and the destruction of the whole element appeared for this reason. Finally, what should be pointed out, although from the statistical point of view of only three samples was small and the associated variability of the results in some series was high, the study results and conclusions confirmed the ones of other researchers in this topic. Certainly, in some cases the high results variability was a result of the above mentioned material imperfections of wood and not a result of the static behaviour of the joints. Nevertheless, the tests results and conclusions presented in this paper may consist a great help, not only for the researchers, but above all for the engineers and conseravators when working with the carpentry joints in historic and historical objects. Acknowledgements The research was carried out as part of the research project no. 2015/19/N/ST8/00787 funded by the National Science Centre. References Ross P. (2002). Appraisal and repair of timber structures. Thomas Telford Ltd, London. Jasieńko J., Nowak T., Karolak A. (2014). Historical carpentry joints. Journal of Heritage Conservation, 40, 58 - 82. Karolak A, Jasieńko J, Raszczuk K. (2020). Historical scarf and splice carpentry joints: state of the art. Heritage Science, 8, 105 Corradi M.; Osofero A.I.; Borri A. (2019). Repair and Reinforcement of Historic Timber Structures with Stainless Steel – A Review. Metals, 9, 106. Rapp P. (2015). Methodology and examples of revalorization of wooden structures in historic buildings. Journal of Heritage Conservation, 43, 92 108. Perez L. P. (2003). Design and construction of timber roof structures, built over different structural systems. Cases studium at the Valencia Community. In: Proceedings of the First International Congress on Construction History, Madrid, Spain, 20 - 24 January, 2003. Tampone G., Semplici M. (2006). Rescuing the Hidden European Wooden Churches Heritage, An International Methodology for Implementing a Data Base for Restoration Projects. In cooperation with Fly Events and Alter Ego Ing Arch S.r.l. (a Subsidiary Company of the Collegio degli Ingegneri della Toscana), Città di Castello. Parisi M. A., Piazza M. (2008). Seismic strengthening of traditional carpentry joints. In: Proceedings of the 14th World Conference on Earthquake Engineering, Beijing, China, 12 - 17 October 2008.