Out-of-plane shake-table tests of strengthened multi-leaf stone masonry walls

Existing unreinforced multi-leaf stone masonry (URM) buildings are one of the most earthquake prone types of construction. Failure typically occurs even at low levels of earthquake-induced loads, with the out-of-plane delamination of masonry leaves and consequent collapse of the whole fa double dagger ade. Although this issue has been tackled by several researchers, dynamic tests reproducing the earthquake behaviour of as-built and strengthened multi-leaf stone URM walls are very limited in the literature. In response to this lack, shake-table testing of eight full-scale multi-leaf stone masonry walls followed by dynamic modal identification was performed. The application of steel tie-rods in the wall cross-section, the injection of the inner-core using hydraulic lime-based grout, and a combination of the two techniques are presented herein as suitable interventions to enhance the monolithic behaviour of multi-leaf stone URM walls. Tying the outer masonry leaves together increased the seismic capacity by a factor of 1.8 compared to unreinforced condition, while injecting grout into the inner-core of the wall provided resistance to peak ground acceleration (PGA) that were 2.3-3.6 times the PGA resisted by as-built walls, depending on the quality in the execution of the intervention. The results obtained in the walls strengthened with both techniques were significantly related to the grout injection only.