Seismic retrofitting of low-rise masonry and concrete walls using steel strips

Four concrete block masonry and two reinforced concrete walls were designed to simulate low-rise nonductile walls built decades ago, before the enactment of earthquake-resistant design provisions. Two masonry walls were unreinforced and two were partially reinforced. The concrete walls had minimum reinforcement. One wall from each pair was retrofitted using a steel strip system consisting of diagonal and vertical strips that were attached using through-thickness bolts. Stiff steel angles and anchor bolts were used to connect the steel strips to the foundation and the top loading beam. All walls were tested under combined constant gravity load and incrementally increasing in-plane lateral deformation reversals. The lightly reinforced concrete walls were also repaired using only vertical strips and retested. These tests showed that the complete steel-strip system was effective in significantly increasing the in-plane strength and ductility of low-rise unreinforced and partially reinforced masonry walls, and lightly reinforced concrete walls.