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2. Reusing timber for a circular, low-carbon future : challenges and the path forwardMohammad Derikvand, 2026, drugi znanstveni članki Opis: Load-bearing timber is usually not reused in a second structural application after its first service life, not due to proven inadequacy, but largely because prevailing standards recognize only first-use material. When buildings are dismantled, the recovered timber is typically routed toward energy recovery, re- or down-cycling, or disposal, while functionally equivalent components for new construction are manufactured from newly harvested logs. The current regulatory framework favors virgin timber, even where reused elements could technically perform the same structural functions. Therefore, one of the primary barriers to structural timber reuse is the absence of codified pathways for qualification, certification, and market acceptance.
Ključne besede: timber, reuse, reclaimed timber, circular economy, standards and certification
Objavljeno v RUP: 03.02.2026; Ogledov: 627; Prenosov: 7
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3. Moisture-activated set-recovery of thermo-hydro-mechanically densified hardwood dowels for high-tolerance timber connectionsLei Han, Alexander Scharf, Mohammad Derikvand, Matthew Schwarzkopf, Bogdan Mitkovski, Dick Sandberg, Andreja Kutnar, 2026, izvirni znanstveni članek Opis: Conventional wooden dowel connections in timber structures rely on tight press-fit installation, which requires high insertion forces and often loosens over time due to stress relaxation. This study investigates an alternative approach that exploits the moisture-activated set-recovery of thermo-hydro-mechanically (THM) densified hardwood dowels to enable slip-fit assembly followed by self-tightening in service. To this end, European beech and black poplar were densified radially and tangentially at different compression ratios. They were then evaluated for swelling kinetics, swelling pressure, bending performance, and moisture-activated expansion using in-situ X-ray CT in water at 20 °C and 100 °C. Results show that activation kinetics can be controlled by temperature. Expansion was rapid within minutes in hot water and slower but equivalent in magnitude at room temperature. Beech outperformed poplar, with radial densification at 35 % compression ratio producing a peak swelling pressure of 5.7 MPa and a modulus of rupture of 268 MPa after activation. Poplar generated higher free expansion but significantly lower pressure due to its lower stiffness. Radial densification was consistently more effective than tangential, enhancing both expansion magnitude and pressure generation. Capillary uptake triggered expansion along the dowel length (∼30 mm in 1 h) and produced an elliptical expansion profile. Importantly, mechanical strength was retained post-activation, which confirms structural suitability. These results demonstrate that THM-densified beech dowels can offer a robust self-tightening mechanism, combining low-force installation with durable pressure generation and stable mechanical performance. This provides a viable path toward adhesive-free, metal-free, high-tolerance timber connections.
Ključne besede: THM densification, dowel laminated timber, CT scanning
Objavljeno v RUP: 28.01.2026; Ogledov: 820; Prenosov: 0
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4. Long-term durability of flax-glass hybrid FRP-timber composite structures subjected to hygrothermal environment : experimental and simulationSilu Huang, Libo Yan, Bohumil Kasal, Wei Yang, 2025, izvirni znanstveni članek Opis: This paper focuses on the experimental and numerical analysis of long-term performance of flax-glass hybrid FRP (HFRP)-laminated veneer lumber (LVL) joints and beams subjected to hygrothermal environment (50℃ and 95 %RH) for six months. The joints and beams with different fibre fabric stacking sequences of HFRP exposed at different exposure intervals (0, 1, 2, 3 and 6 months) were tested under block shear and four-point bending, respectively. The tensile properties of epoxy and HFRP composites under those exposure intervals were also examined to explore degradation mechanisms of HFRP in LVL-HFRP beams. Tensile strength and strain of HFRP showed a major reduction (26.7 – 32.1 %) in the first month of exposure. Hydrolysis and oxidation of epoxy were found to have insignificant effects on HFRP tensile properties, based on Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) results. A significant decrease (34.7 – 35.7 %) of LVL-HFRP joints in their shear strength was attributed to weakened hydrogen bonds between cellulose and lignin-hemicellulose matrix, along with the degradation and softening of hemicellulose. LVL-GF beams in which the glass fibre layer of HFRP was adhered to LVL exhibited a major reduction in bending strength (23.4 %) after the first month of exposure. In LVL-FG beams where the flax fibre layer was adhered to LVL, a major decrease in bending strength (25.8 %) was observed after two-month exposure. The postponed reduction in LVL-FG beams compared with LVL-GF beams was caused by the slower moisture diffusion in HFRP of LVL-FG beams than that in LVL-GF beams. A diffusion–stress coupled finite element (FE) model was developed, incorporating moisture diffusion and moisture-dependent mechanical properties for both the timber and HFRP components. Based on this model, the flexural response of LVL–HFRP beams after hygrothermal exposure was simulated, showing satisfactory agreement with experimental results. This research developed a step towards the long-term performance evaluation of HFRP-timber composite structures with different fabric stacking sequences of HFRP.
Ključne besede: long-term durability, hybrid FRP, timber-hybrid FRP composite structure
Objavljeno v RUP: 23.12.2025; Ogledov: 704; Prenosov: 3
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5. Experimental and analytical evaluation of shear capacity of reclaimed timber connections with thermo-mechanically densified wooden dowelsMohammad Derikvand, Donya Bazyar Khoshroodi, 2025, izvirni znanstveni članek Opis: The reuse of reclaimed timber in structural applications is increasingly recognized as a strategy to extend ma- terial life cycles and reduce waste. Particular attention has recently turned to reusing reclaimed timber in adhesive-free laminated products with wooden dowels, where connection performance is critical. The aim of this study was to investigate the mechanical performance of double-shear connections assembled from reclaimed spruce timber using thermo-mechanically densified wooden dowels. The dowels were first evaluated in bending and embedment tests on lamellae made from both reclaimed and virgin spruce timber. The shear capacity of the connections was then evaluated in three layups: two homogeneous (all-reclaimed lamellae and all-virgin spruce lamellae) and one hybrid (reclaimed side lamellae with a central virgin spruce lamella). Analytical predictions were performed based on the draft of the new Eurocode 5, however, with two alternative definitions of dowel bending resistance (ultimate moment Mu and yield moment My), and three alternative definitions of embedment strength (f 0.05d h calculated using the 0.05 d offset method, f Fmax h calculated from Fmax, and f 0.8Fmax h calculated from 0.8 Fmax). The three lamellae layups exhibited relatively similar mean capacities (7.3–8.3 kN). The all-reclaimed connections were on average 13 % stronger than the other assemblies, but this was not statistically significant. Among the model input variants, Mu with f 0.05d h showed the closest agreement with the experimental mean values, while My with f 0.05d h led to more conservative predictions preferable for design. In both cases, excluding outliers from the embedment test results reduced overestimation in the predictions. All other input variants overestimated the shear capacity. Overall, both homogeneous and hybrid connections with reclaimed timber lamellae performed comparably to virgin timber connections and exhibited predictable mechanical behavior.
Ključne besede: reclaimed timber, wood densification, structural reuse, embedment strength, dowel connections, European yield model, Eurocode 5
Objavljeno v RUP: 17.12.2025; Ogledov: 758; Prenosov: 7
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6. Vibration-based serviceability and acoustic assessment of timber floorsAngelo Aloisio, Dag Pasca, Thomas Hillberger, Roberto Tomasi, Thomas Reynolds, Chiara Bedon, Sven Vallely, Rok Prislan, Kemal Edip, Mohammadreza Salehi, 2025, samostojni znanstveni sestavek ali poglavje v monografski publikaciji Opis: Timber floors are particularly susceptible to noise and vibration issues when compared to other construction methods, such as concrete floors. This is due to the relatively high stiffness-to-mass-density-ratio of timber floors, which enables so-called ‘lightweight’ floor constructions, in contrast to ‘heavyweight’ floor constructions consisting, for example, of concrete slabs and steel girders.
Ključne besede: vibrations, tall timber buildings, floors
Objavljeno v RUP: 21.10.2025; Ogledov: 740; Prenosov: 8
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8. Feasibility of portable NIR spectrometer for quality assurance in glue-laminated timber productionJakub Michal Sandak, Peter Niemz, Andreas Hänsel, Juana Mai, Anna Malgorzata Sandak, 2021, izvirni znanstveni članek Ključne besede: near infrared spectroscopy, glue-laminated timber, glulam, delamination, quality assurance
Objavljeno v RUP: 18.10.2021; Ogledov: 5178; Prenosov: 27
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