Flexural strengthening of RC members by means of CFRP laminates: general issues and improvements in the technique

In the last decade Fibre Reinforced Polymers (FRP) have become a promising category of materials in Civil Engineering. Their use as externally bonded reinforcement (FRP EBR) for strengthening of structural bearing members is already a well documented technique in several countries. Often it appears in the design that FRP EBR can only be used at a fairly limited stress, due to e.g. debonding failure modes. Newly developed FRP materials offer new possibilities to improve the effectiveness of the strengthening. In this paper the use of special multi-directional laminates with extra bolted anchorage is discussed, based on a test programme recently carried out at the Magnel Laboratory for Concrete Research. The test results show how this technique can prevent or postpone some debonding failure modes, thus leading to a higher strengthening factor. Also, the deformability at ultimate can be significantly improved (so-called "pseudo-ductile behaviour").