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Abstract: The increased use of engineered wood in the built environment is attracting much attention because of the significant sustainable attributes. The formation of high quality reliable structural adhesive bonds is essential during the manufacture of such products. This research examines and compares the performance of bonded European beech and Radiata pine subject to natural weathering, comparing untreated, preservative treated and mineralized wood. Bonded joints were naturally weathered in Slovenia and New Zealand, respectively. The fracture energy was evaluated through Mode I fracture tests using the double cantilever beam arrangement at various ageing stages. FTIR analysis was conducted to assess chemical changes in the adhesives and wood substrate. The research provides insights into the interactions between ageing, wood species, and adhesive performance, enhancing timber structures sustainability.
Keywords: durability, weathering, climate, adhesive bond, mode I fracture testing
Published in DiRROS: 27.08.2025; Views: 483; Downloads: 202
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Abstract: This review paper explores the concepts of overstrength and ductility as fundamental components of capacity- based design with a focus on timber engineering. It addresses the necessity of implementing overstrength and capacity-based design principles for effectively managing both accidental and characteristic load scenarios. Current approaches define overstrength either within the Load and Resistance Factor Design (LRFD) framework or by means of structural reliability analyses at component level, both with clear limitations in controlling the overall structural reliability and the target failure hierarchy, which is exemplified and demonstrated by a parameter study. In response, a new thematic approach for overstrength factors is proposed, formulated within the structural reliability framework, which enhances the understanding and application of ductility in design. This new methodology is benchmarked against existing approaches, therefore demonstrating its effectiveness. A clear and concise definition of ductility is emphasised as essential for a meaningful application of capacity-based design in clear conjunction with the concept of overstrength. The aim is to create a clear classification of component failure modes either as brittle (non-dissipative, non-ductile) or ductile (and dissipative, i.e. connections which provide also ductility in reverse loadings without severe pinching), which is crucial for reliably achieving a failure hierarchy where ductile failures precede brittle failures. The findings underline the importance of integrating overstrength and ductility into timber engineering practice to improve structural safety and at the same time to achieve resilient designs.
Keywords: overstrength, timber engineering, connections, joints, ductile failure, brittle failure
Published in DiRROS: 14.07.2025; Views: 425; Downloads: 224
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Abstract: Experimental tests of Cross Laminated Timber (CLT) under in-plane beam loading conditions are presented. The influence of the element layup, the individual lamination width, and the beam overhang at the supports on the shear force capacity was investigated. All the CLT beams had the same gross cross section, and a 4-point-bending test setup was used. The experimentally determined load-bearing capacities are compared with the load-bearing capacities resulting from analytical methods proposed for structural design, focusing on shear failure in the crossing areas of flatwise bonded laminations (shear failure mode III). The test results indicate no or very small influence of the element layup and the lamination width on the shear force capacity. These results partly contradict the predictions of the proposed design methods. Of the three studied beam geometry parameters, the beam overhang at the support had the greatest influence on the load-bearing capacity.
Keywords: cross laminated timber, CLT, beam, shear testing, shear capacity, design methods
Published in DiRROS: 15.04.2024; Views: 1384; Downloads: 724
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Abstract: This paper presents results from an experimental assessment of glued-in rods in cross laminated timber (CLT). For the purposes of the study more than 60 pull-pull tests were performed, where the specimens varied in terms of bonded-in length (from 80 to 400 mm), rod diameter (16-24 mm) and rod-to-grain angle (parallel and perpendicular). Several different failure modes that are not common for other applications of glued-in rods (e.g., a failure between CLT layers) were obtained for the analysed CLT specimens. It was found that these failure mechanisms can substantially influence the obtained ultimate tension loads. At the end, the experimental results were compared with empirical and semi-empirical equations for estimating the pull-out strength of glued-in rods in structural timber and glulam. The comparison showed that most of the existing equations overestimate the ultimate tension loads for specimens with the rod parallel to the grain and underestimate the ultimate tension load for specimens with the rod perpendicular to the grain. The results vary because the possible CLT failure modes were not included in previous studies. Further studies are proposed to improve the equations for glued-in rods in CLT.
Keywords: glued-in rods, cross laminated timber (CLT), pull-pull experiment, glued-in length, rod-to-grain angle, failure mechanisms in CLT
Published in DiRROS: 29.11.2023; Views: 1298; Downloads: 1014
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Abstract: Numerical simulations and parametric studies of glued-in rods in cross-laminated timber have been performed. The simulations were based on 3D finite element analysis, using a cohesive surface model for the bond-lines between the laminations and the bond-line along the rod. The parametric studies investigated the influence of the glued-in length, the rod diameter, and the rod-to-grain angle on the load-bearing capacity and stiffness of the connection. The analyses showed that the load-bearing capacity generally increases with the glued-in length and the rod diameter, which agrees well with experiments. For different rod-to-grain angles, different mechanical behaviour was observed, especially considering the failure modes.
Keywords: glued-in rods, cross laminated timber (CLT), parametric study, nonlinear numerical modelling, glued-in length, rod diameter, rod orientation
Published in DiRROS: 13.09.2023; Views: 1544; Downloads: 801
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