Study on flexural behaviour of glulam beams reinforced by Near Surface Mounted (NSM) CFRP laminates

• NSM-CFRP reinforcement was adopted for reinforcing glulam beams made by Douglas fir and Poplar.
• The flexural behaviour of the glulam beams was improved significantly by using NSM-CFRP reinforcement.
• The glulam beams reinforced by NSM-CFRP reinforcement exhibit pseudo-ductile behaviour.
• The reinforcement in the tension zone was seen to lower the location of the neutral axis of the reinforced beams.

Near Surface Mounted (NSM) reinforcement is an effective strengthening technique for timber engineering. This study investigated the flexural behaviour of glulam beams reinforced by NSM–CFRP laminates. A total of twenty-four glulam beams, including eighteen reinforced glulam beams and six unreinforced glulam beams were tested up to failure to evaluate the reinforcing effect in terms of the flexural strength and the flexural stiffness of the beams. Two types of timber, namely, Douglas fir and Poplar were taken for the tests. The ratio of reinforcement arranged from 0.331% to 1.322%. The experimental results indicate that the flexural strength and the flexural stiffness were significantly improved by 34.2%–52.3% and 8%–28.5%, respectively. Several reinforced beams exhibit the pseudo-ductile behaviour in comparison to the linear elastic behaviour of the unreinforced beams characterized by the brittle tensile failure. The strain profile distribution indicates that the compressive behaviour of the timber can be improved by using NSM–CFRP reinforcement at the tension zone of the beams. Theoretical analysis was adopted for the prediction of the flexural strength of the glulam beams and the predicted results was observed in good agreement with the experimental results of the tested beams.