Flexural performance of glulam strengthened with flax-fiber reinforced polymer composites

Glulam is a construction material widely used all over the world. Common glulam often exhibits brittle damage under bending loads due to natural defects in the wood, which results in low load-bearing arid deformation capacities. To improve the flexural performance of glulam beams, a new type of glulam longitudinally strengthened with flax-fiber reinforced polymer (FFRP) composites is proposed. Eighteen full-scale timber beams with and without FFRP were tested, where the bonding length and the bonding layers of the FFRP are varied for FFRP strengthened beams. Results demonstrate that the flexural performance of strengthened beams improves significantly with increasing bonding length. The number of layers of FFRP had a minor effect on the flexural performance when the bonding length was 2700 mm. Moreover, the reliability of load capacity of beams can be improved by bonding FFRP with lengths over 1400 mm. A theoretical calculation predicts the ultimate flexural capacity of the strengthened beam, and exhibits good agreement with the experimental results. Finally, a cost analysis is made to evaluate the economics of various reinforcement methods, indicating that three-layer FFRP of 2700 mm strengthening length significantly increases the flexural performance at lower cost than other strengthened types.