Probabilistic strength domains of masonry walls reinforced with externally bonded composites

Unreinforced masonry (URM) has been used to build up a large number of structures and infrastructures since ancient times, and is still employed in modern construction. In recent earthquakes, URM buildings have sustained a high degree of damage due to in-plane loading, demonstrating a pressing need for retrofitting. In the last years, externally bonded fibre-reinforced polymers (FRPs) and fabric-reinforced cementitious matrices (FRCMs) have been proposed as effective solutions for seismic retrofit of URM walls and their use is rapidly increasing worldwide. In this paper, the in-plane lateral strength of tuff stone masonry walls in both as-built and strengthened conditions is investigated. Diagonal FRP strips and FRCM composite, applied on both sides of walls and through single plies, are considered as strengthening systems. Based on capacity models as well as statistics and probability distributions for material properties, geometry and models, a probabilistic analysis was carried out by using plain Monte Carlo simulation. The output of that analysis consists of shear force versus axial force strength domains corresponding to the 16th, 50th and 84th percentile levels. Simplified equations, in a dimensionless format, are finally provided by using robust regression. Such an output represents a practice-oriented tool for both design and assessment of externally-strengthened masonry walls.