EXTERNAL FRP REINFORCEMENT OF DOUGLAS FIR BEAMS IN BENDING

The use of bonded Fiber Reinforced Polymer laminates for strengthening solid wood structural members is receiving increasing attention in recent years, especially for structural rehabilitation purposes, where existing solid members may present natural defects, significant inclination of the grain direction and initial cracking. The paper experimentally investigates the bending strengthening of solid Douglas Fir beams, with axis parallel or inclined to the grain direction, through the application of a Carbon Fiber Reinforced Polymer glued by an epoxy resin on the tension side of the beams only. Reinforcement thickness, presence and position of steel reinforcement in compression are also accounted as additional parameters. Finally, some beams were loaded till cracking, successively reinforced and re-loaded till failure to assess the effects of the reinforcement on a significantly damaged element. The increment in bending performances due to the application of CFRP is discussed, as well as the effectiveness of the addition of the metal reinforcement, also depending on the initial damage level of the beam. To the structural rehabilitation purposes, it is shown how large variations in mechanical performances of timber elements, due to natural defects of woods or to inclination of the grain direction, may be reduced by the introduction of the CFRP reinforcement