Strengthening of Masonry: Opportunities and Challenges in the Use of Composites

ABSTRACT

The worldwide engineering community has identified failures of Unreinforced masonry (URM) walls as one of the major causes of material damage and loss of human life due to seismic events. Therefore, the development of effective and affordable retrofitting techniques for masonry members is an urgent need. To date, previous works on URM and reinforced masonry walls strengthened with fiber reinforced polymeric (FRP) materials have shown notable increases in capacity and ductility. Unfortunately, field applications involving the use of FRP laminate on masonry members may be carried out even if not supported by rigorous experimental background. The cause of that is the implicit assumption that the high performances of FRP should always benefit a compromised structural situation. Part of the present experimental programs (i.e. bond tests, out-of-plane behavior with arching effect, inplane behavior) shows the detrimental effects produced by inaccurate design. Conclusions and recommendations are provided for all the studied issues. Use of FRP materials is not limited to strengthen walls subjected to out-of-plane and in-plane loads, but can be in the form of tendons in pre-stressing applications. This could be a new fronteer for the FRP materials because of advantages over steel tendons such as light weight, resistance to corrosion, lower or higher elastic modulus etc. A major problem facing the use of FRP in pre-stressing applications is the anchorage. The new anchor system showed in section 7 demonstrated that FRP can be succefully used for the postensioning of masonry in substitution of steel. A technical obstacle preventing the extended use of FRP materials in construction is a lack of long-term and durability performance data comparable to the body of knowledge available for traditional construction materials. A durability test was conducted as part of this thesis on a type of putty (used to prepare the surface) to demonstrate the implications of this concern.