Flexural behaviour of old wooden beams strengthened with CFRP: Experimental and numerical investigations

Abstract

The flexural performance of old wooden beams strengthened with Carbon Fiber Reinforced Polymer (CFRP) strips was investigated through a combination of experimental and numerical analyses. Timber specimens were sourced from three historic wooden structures in Türkiye. CFRP strips were bonded to the tension zone of the beams to enhance flexural performance, while transverse CFRP strips were applied at regular intervals to improve shear resistance. A total of thirty-one beam specimens, varying in wood type, span length, and CFRP strip spacing, were tested under three-point bending. Key variables included chestnut and elm wood, span lengths of 300–700 mm, and CFRP strip spacings of 50 mm, 75 mm, and 100 mm. Beams with 50 mm strip spacing (S5) exhibited the highest values with load capacity (52.7 kN), stiffness (3.55 kN/mm) occurred in elm beams, while the largest displacement (25.3 mm) and energy dissipation (494 kN-mm) occurred in chestnut beams. Digital Image Correlation (DIC) was employed to assess strain distributions, while numerical models were developed using finite element analysis (FEA) to validate experimental results. DIC analysis confirmed that peak strains occurred near the loading point, while minimum strains were observed at the supports. FEA models closely matched experimental data, with parameter ratios mostly ranging between 0.64 and 1.16, confirming their reliability. The numerical analysis aligned closely with experimental outcomes, showcasing its effectiveness in modelling the anisotropic and heterogeneous nature of timber. These findings highlight CFRP’s effectiveness in strengthening and preserving historic wooden structures, offering a sustainable solution for modern timber engineering applications.