Lateral Loading Tests on a Masonry System With and Without External Reinforcement

Three lateral loading tests on an unreinforced masonry (URM) wall with a opening are presented. The wall was made up of tuff masonry and pozzolana-based mortar, and consisted of two piers connected by a spandrel with a wood lintel upon the opening. The gross dimensions of the masonry wall were: length of 510 cm; height equal to 382 cm; and thickness of 31 cm. All tests were performed in a quasi-static mode to assess structural performance at different damage levels, for instance in terms of lateral force and displacement at peak state of the capacity curve, stiffness and strength degradation, energy dissipation, hierarchy of collapse modes. Mechanical characterization of tuff masonry was preliminarily carried out either in uniaxial compression along the main directions of URM prisms, or in diagonal compression on prisms strengthened with inorganic matrix-grid (IMG) composites. The first lateral loading test was carried out on the original wall in monotonic regime up to a drift of 0.92%, namely a moderate damage level. The second test was performed by applying cyclic displacements until a drift of 1.28% was attained. The damage in the wall was rather low, so the masonry wall was lightly repaired and the spandrel was strengthened with IMG composites. The strengthened model was then tested once again under cyclic loading up to a drift of 2.75%. Such a test provided valuable information on the post-cracking stiffness and strength characteristics of the masonry system, as well as its displacement capacity. The aim of the experimental program was to investigate the contribution of spandrels to both load-bearing and displacement capacity of masonry walls. The experimental set-up allowed to avoid any given boundary condition to the spandrel. The laboratory tests showed that: (1) most part of damage spread within the spandrel panel, first, and at the base of piers, after, due to rocking failure mode; (2) the cyclic behaviour of the wall could be defined through a degrading bilinear force-displacement relationship; and (3) the strengthening technique allowed not only to restore the load-bearing capacity of the original wall, but also to reduce the strength degradation.