Provisional design guidelines for the strengthening of masonry structures subject to in-plane loading

Masonry structures constitute a large percentage of the current buildings in most countries around the world. Structural weakness or overloading, dynamic vibrations, settlements, and in-plane and out-of-plane deformations can cause failure of unreinforced masonry (URM) structures. URM buildings have features that, in case of overstressing, can threaten human lives. These include unbraced parapets, inadequate connections to the roof, floor and slabs, and the brittle nature of the URM elements. Organizations such as The Masonry Society (TMS) and the Federal Emergency Management Agency (FEMA) have determined that failures of URM walls result in more material damage and loss of human life during earthquakes than any other type of structural element. In the last years, a growing interest has been direct to the application of FRP (Fiber Reinforced Polymer) materials as strengthening materials because they may provide solutions for the strengthening of masonry due to their easy application and their favourable structural performances. Nowadays few design guidelines are available to apply FRP on masonry structures. This paper presents a proposal for design recommendations for shear strengthening of unreinforced masonry walls with FRP systems. The proposed design protocol is within existing building codes for traditional materials and takes into account the recent experimental researches. The adopted methodology offers a rational attempt of in-plane upgrade of structural masonry walls with bonded FRP systems.