1. Structural fire behaviourFelix Wiesner, Daniel Brandon, Andrea Lucherini, Pedro Palma, 2025, independent scientific component part or a chapter in a monograph Abstract: Fire safety and fire protection objectives require that buildings and parts of buildings do not collapse during a fire. This requires that the load-carrying capacity is maintained to a minimum acceptable level during a fire. This chapter briefly describes the historical background and state of the art of fire resistance and its determination for timber members through testing or calculations. The thermal and mechanical principles that underpin structural behaviour of wood at elevated temperatures are explained in the context of explicit calculation methods that enable explicit evaluation of the structural capacity beyond fire resistance, which is a formalised and codified assessment of structural elements against a standard fire. The importance of connections to the overall structure in fire is explained along with suitable design considerations. Ultimately, knowledge gaps with respect to novel and more complex engineered timber products for taller timber buildings are highlighted alongside potential limitations of established design parameters.
Keywords: fire resistance, fire safety, structures, load-carrying capacity, timber, connections
Published in DiRROS: 18.11.2025; Views: 281; Downloads: 118
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2. Overstrength in timber engineering : general discussion and proposal for a more reliable and broader applicationReinhard Brandner, Boris Azinović, 2025, original scientific article 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: 431; Downloads: 226
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3. Influence of test methodology on the characterization of the parallel-to-grain timber embedment strength and foundation modulus of dowelsCaroline D. Aquino, Rodrigues Leonardo G., Michael Schweigler, Meta Kržan, Zheng Li, Jorge M. Branco, 2024, original scientific article Abstract: A reliable determination of the embedment strength and foundation modulus of timber elements is critical for the design and safety assessment of joints in timber structures. However, the existence of various test configurations for characterising the embedding properties of large diameter steel fasteners in timber elements poses challenges in directly comparing and utilising available test data. This paper aims to provide an insight into the influence of embedment property test methods, comparing experimental results from different test setups within the guidelines of the EN 383 and ASTM D 5764-97a standards for European softwood species, Scots pine wood (Pinus sylvestris) and Norway spruce (Picea abies). In addition to the test guidelines, the thickness of the specimen and the application of the load was evaluated within the protocols. A comprehensive statistical analysis was performed to identify statistically significant differences between the groups evaluated. The results of the analysis revealed disagreement between the standards in the evaluation of the strength of the embedding, highlighting the potential bias inserted by the experimental setup and protocol. Furthermore, it was proven that the thickness of the specimens influences both the embedding strength and the foundation modulus of the wood species tested. Finally, no distinctions were observed between tensile and compressive loading within the guidelines of the EN 383 standard.
Keywords: embedment strength, foundation modulus, dowel-type connections, test methods
Published in DiRROS: 15.04.2024; Views: 1186; Downloads: 770
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4. Flexible polymer connections for clt structuresBoris Azinović, Andreja Pondelak, Jaka Gašper Pečnik, Václav Sebera, 2020, published scientific conference contribution Abstract: This paper explores the possibility of using flexible polymer adhesives to dissipate energy in CLT buildings during earthquakes. In the first series of tests, pull-off tests of various polyurethane (PUR) adhesives were performed. The connection was tested in pull-pull configuration using monotonic, tension-only loading. The tests have shown that the adhesive can resist large deformations already in tension loading and with small thicknesses of the bond-line. Based on the pull-off test results, one adhesive has been selected for further testing. Monotonic lap-shear tests were performed with the selected adhesive and thick bond-line (3 mm and 6 mm). The results show, that the standard method for lap-shear testing (EN 205) needs to be adapted for thick glue-line. It was found that the strength of 3 mm glue-line is higher than 6mm one, which is in agreement with adhesion theory. The flexible PUR adhesives could potentially be used in CLT structures for anchoring the CLT wall with “flexible” glued-in rods or as a “flexible” vertical shear connection between the CLT walls. Such systems have a potential to dissipate energy in seismic areas.
Keywords: CLT connections, flexible adhesive, polyurethane, energy dissipation, pull-off, lap-shear
Published in DiRROS: 19.01.2024; Views: 1488; Downloads: 700
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5. Brittle failure of laterally loaded self-tapping screw connections for cross-laminated timber structuresBoris Azinović, José Manuel Cabrero, Henrik Danielsson, Tomaž Pazlar, 2022, original scientific article Abstract: The performance of structural timber connections is of utmost importance since they control the global response of the building. A ductile failure mechanism on the global scale is desirable, especially in the design of structures in seismic areas, where dissipative components in which ductile failure modes need to be ensured are considered. Therefore, the knowledge of possible brittle failure modes of connections is crucial. The paper investigates the brittle failures of laterally loaded dowel-type connections in cross-laminated timber subjected to tensile load in a lap joint configuration through experimental investigations and analytical estimations. A set of 13 different test series has been performed with fully threaded self-tapping screws of 8 mm diameter and different lengths (40 to 100 mm) in cross-laminated timber composed of 3 or 5 layers (layer thickness range from 20 to 40 mm), giving rise to the activation of different brittle failure modes at different depths. Plug shear was among the most typically observed failure modes. A previously proposed model for the brittle capacity was applied to the tested connections at the characteristic level. As shown by the performed statistical analysis, the existing model is not reliable and mainly unconservative. A very low performance is observed (CCC = 0.299), but with a good correlation (c = 0.750) for the tests in the parallel direction. Further research work is required to improve the current model predictions and to gain a better understanding of the underlying resisting mechanisms.
Keywords: cross-laminated timber, dowel type fasteners, connections, brittle failure, experimental investigations, self tapping screws, open access
Published in DiRROS: 31.05.2023; Views: 1307; Downloads: 798
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