Strengthening Historical Masonry with FRP or FRCM: Trends in Design Approach

Over the past two decades, composite materials, in forms of Fiber Reinforced Polymers (FRP), have been widely spread worldwide in the field of civil and monumental construction. Design guidelines and provisions were developed and provided by national and international institutions. In the last years, a new generation of materials, named Fabric Reinforced Cementitious Matrix (FRCM) were introduced as strengthening devices for concrete and masonry structures. Their application in the field of historical masonry has grown as a result of the recent Italian earthquakes. In this paper, starting from a retrospective on what has been done in recent years in the field of FRP applications, insights will be discussed for future research and applications of FRP and FRCM in heritage buildings. Some differences between FRP and FRCM materials will be highlighted, in terms of fiber-matrix interface and delamination mechanisms. The different micromechanical behavior in terms of fracture energy will be highlighted, and the macro-mechanical implications in terms of ductility will be pointed out, as a first attempt to quantify this complex problem. By considering the last innovative and pioneering applications of FRP/FRCM in heritage buildings, criteria for structural enhancement will be shown and discussed. This is done with a special focus on the ability, shown by these new technologies, to inhibit failure mechanisms in masonry artifacts.