Masonry retrofitting with steel reinforced plaster: experimental and analytical study

Steel reinforced overlay is a common retrofitting technique adopted to improve the performance of existing masonry buildings under seismic loads, both in-plane and out-of-plane. This paper presents the results of an experimental program aimed at assessing the effectiveness of steel reinforced plaster in improving the performance of masonry walls under cyclic loads, analysing the effect of the main design parameters. Diagonal compression tests were performed under displacement control. Unreinforced specimens were also tested as reference. The investigated parameters were: the masonry thickness (250 or 380 mm), the overlay thicknesses (30 or 50mm), the type of mortar used for the overlay (. cementitious or lime-based), and the number of connectors (8 or 12 for each side of the specimen). An analytical approach, previously presented by the authors, is recalled and further validated using the new experimental data, and a parametric study is performed to better discuss the effect of some design parameters. The results show that the load capacity of specimens retrofitted with lime-based plaster resulted at least equivalent to the one retrofitted using the most common cementitious one, and in some cases superior, with higher displacement at the ultimate load. Higher overlay thickness has a positive effect in terms of post-peak ductility for the cementitious plaster, and higher load bearing capacity for the lime plaster. An increasing number of connectors does not affect the ultimate load but results in a late detachment of the plaster layers. The analytical method results still valid by considering the new presented experimental data. The parametric study confirms that the strength and thickness of the overlay are crucial for the load bearing capacity of the specimen, while the number of connectors does not affect significantly the ultimate load. • The effectiveness of steel reinforced plaster was experimentally studied • Cyclic diagonal tests were performed on unreinforced and retrofitted masonry walls • The influence on the performance of several design parameters was investigated • The strength and thickness of the overlay are crucial for the load bearing capacity • The number of connectors does not affect significantly the ultimate load