Fibre-based composite materials for the seismic strengthening of masonry ring beams: cyclic tests on full-scale samples

In masonry buildings, ring beams are crucial structural components for preventing out-of-plane failure of walls and fostering global seismic responses. The traditional approach of building reinforced concrete ring beams in existing structures is very invasive, which has motivated present research into new ways of constructing using modern fibre-based composite materials. Two solutions are tested by quasi-static, horizontal bending cyclic tests on full-scale, solid brick and rubble stone masonry. The first solution consists of horizontal Carbon Fibre–Reinforced Polymer (CFRP) strips externally bonded on the outer masonry surface, while the second comprises embedded Glass Fibre-Reinforced Polymer (GFRP) meshes in the masonry bed joints. Simplified analytical models are applied to estimate the strength. Although CFRP strips are applied eccentrically, they proved effective for loads in both directions (the fibres fractured in tension) because of the continuity of the reinforcement throughout orthogonal walls. The ring beams with GFRP-reinforced bed joints responded very well, as evidenced by tensile fracture of fibres. In both cases, bending resistance was significantly improved. However, tests also showed the importance of certain details to avoid stress concentrations in the fibres (e.g. rounded masonry corners) and bed joint slippage (e.g. full embedment of the GFRP meshes with the mortar).