Iskanje po repozitoriju

Opis: Reusing timber in load-bearing applications is a strategy for extending material lifecycles and reducing the environmental impact of construction. However, uncertainty in mechanical properties of reclaimed timber due to the absence of standardized strength grading is a key barrier. The aim of this study was to produce and evaluate the bending properties of dowel-laminated timber (DLT) from reclaimed boards and to assess whether its bending stiffness can be predicted from board-level non-destructive testing (NDT) data. For this, several reclaimed spruce beams with ~200 years of service life were obtained from a heritage building. The beams were 3D-imaged, sawn into boards, and the recovery yield was calculated. The relationship between the dynamic (Edyn) and static (Em,g) modulus of elasticity of the boards was evaluated and benchmarked against virgin boards (strength class C24). DLT specimens with beech dowels were then produced using a stiffness-informed lamination process in three configurations: (i) DLT from reclaimed boards, (ii) DLT from virgin boards, and (iii) hybrid DLT combining reclaimed and virgin boards. The DLT specimens were tested in bending until failure. Based on the results, the recovery yield after initial sawing was 79%, calculated as the volume of the sawn boards relative to the volume of the beams. After defect removal and planing, the recovery yield decreased to 32.1% for the final full-length boards plus about 1.9% shorter pieces. Service-related biological and physical degradations had a greater in- fluence on the recovery yield than the sawing process itself. A strong relationship (R² = 0.823) was found be- tween Edyn of the reclaimed boards before defect removal and planing and their Em,g after full processing. The DLT specimens from the reclaimed boards exhibited bending strength and stiffness comparable to those of DLT from the virgin boards. A simplified analytical model based on board-level stiffness (Edyn or Em,g) predicted the average DLT bending stiffness within ±2%. Overall, the findings demonstrate that stiffness-informed lamination based on board-level NDT can be used to produce DLT from reclaimed timber with predictable performance
Ključne besede: reuse, repurpusing, reclaimed timber, recovered timber, beech dowels, DLT, non-destructive testing, bending test, dynamic modulus of elasticity, failure analysis
Objavljeno v RUP: 14.09.2026; Ogledov: 327; Prenosov: 23
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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: 1066; Prenosov: 11
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