Out-of-plane strengthening of unreinforced masonry walls using near surface mounted fibre reinforced polymer strips

The development of cost effective and minimally-invasive seismic retrofit techniques is required for clay brick unreinforced masonry (URM) buildings because of their poor performance in past earthquakes. A laboratory-based experimental program was implemented to address this need, having well-defined but artificial boundary conditions, and utilising constituent construction materials that replicated the characteristics of masonry found in historic URM buildings. The purpose of this experimental program was to investigate the performance of near-surface mounted (NSM) carbon fibre reinforced polymer (CFRP) strips as a seismic retrofit solution for improving the out-of-plane performance of walls in URM buildings. In the experimental testing program nine masonry beams and five full-scale masonry walls were tested. Details of the design methodology for flexural retrofit of URM walls using the NSM CFRP retrofit technique and laboratory test results are reported. The results of the experimental tests confirmed that the NSM CFRP retrofit technique is a minimally-invasive option for seismic strengthening of URM walls to resist out-of-plane earthquake induced lateral forces. Two recent case-study projects that implemented the NSM CFRP technique are also briefly presented.