Cyclic in-plane shear behaviour of unreinforced masonry panels retrofitted with fibre reinforced polymer strips

An experimental study was conducted to assess the effect on strength and ductility of retrofitting unreinforced masonry (URM) shear panels with near surface mounted (NSM) fibre reinforced polymer (FRP) strips. A total of six wall panels, 1200mm x 1200mm, were subjected to vertical precompression combined with increasing reversing cycles of in-plane lateral displacement. The panels were tested first as URM, retrofitted with NSM FRP strips and then retested. The URM testing was conducted as part of a previous research study to investigate the effects of a damp proof course (DPC) layer incorporated near the base of the panels. The six panels failed in compression, with crushing at the corners and near-vertical cracking throughout the panels in the URM tests. For the current study, the panels were retrofitted using three different arrangements of FRP strip reinforcement and then retested using the same apparatus but with base sliding at the DPC level prevented. The tests were used to determine the effect on strength, displacement capacity and ductility achieved by FRP retrofitting the damaged URM panels compared to the original undamaged panels. The broader aim of the research is to identify techniques for improving the seismic performance of existing URM walls under in-plane shear loading