THE USE OF FRP COMPOSITES TO ENHANCE THE STRUCTURAL PERFORMANCE OF TIMBER BEAMS

摘要

The structural performance of timber can be significantly improved using the well-established technique of glue laminating. The addition of reinforcement in the form of fibre reinforced polymer (FRP) composites can further enhance the strength and stiffness of laminated beams. This paper describes on-going work combining reinforcement with laminated beams fabricated with Irish grown softwood. Britain and Ireland are self sufficient in terms of timber volume. However, in comparison with other countries which have and abundant supply of timber, they do not make the most effective use of this renewable natural resource. It makes sound economic and environmental sense to promote home-grown timber in higher value end uses, so that it can substitute imported timber. The dominant species, Sitka spruce, is characterised by low density, small sizes, presence of knots and the tendency to distort when kiln dried. Laminating eliminates or mitigates the effects of most of these disadvantages while enhancing the structural performance of the source timber. This improvement is most marked with low quality donor timber. The addition of FRP composite reinforcement has been found to suppress tension failure in the timber. Theoretical models have been developed simultaneously with experimental prototypes. Beam testing has progressed from small span beams with tension and compression reinforcement. The paper includes recent work concentrating on the detailed study of failure modes. In this respect, it has been found that the behaviour of reinforced beams at failure is more consistent compared with that of non-reinforced Sitka spruce beams, which are more influenced by the inherent variability of the timber.