Strengthening of Existing Timber Beams with NSM CFRP Plates

In order to reduce the environmental impact of the construction industry, retrofitting/strengthening of existing buildings should be preferred to demolition and re-construction. In most cases, retrofitting should not significantly alter the geometry and aspect of the member and at the same time increase its strength and/or stiffness. For buildings including timber structural members, specific techniques are needed to reach these goals. Within this context, the near surface mounted (NSM) strengthening technique is a possible solution to strengthen timber members without changing their aspect/geometry. This technique consists of bonding a reinforcing profile into a groove cut within the member surface. Often, reinforcing profiles are made of fiber-reinforced polymer (FRP) composites bonded with epoxy resin, since they have a high strength-to-weight ratio and do not suffer from corrosion. In this paper, an experimental campaign is conducted to study the bending behavior of timber beams strengthened with NSM carbon FRP (CFRP) plates applied with an epoxy resin. Four direct-shear tests are first conducted on CFRP-timber joints. Peak loads and interfacial slips are obtained. Then, three three-point bending tests are performed to assess the bending capacity of the strengthened members. Load-deflection curve, peak load, and failure mode of the specimens are provided and discussed.