Prestressing systems for R.C. elements: traditional vs. innovative anchorages

Efforts of researchers during the past thirty years led to a satisfactory knowledge of anchorage systems for FRP (Fiber-Reinforced Polymer) composite cables. Different models can be found in the technical literature, divided into bonded and split wedge anchorages. As far as split-wedge anchorages are concerned, they descend from the pioneering steel wedged anchorage for two metallic rods patented in the early 1900 by the French Eugène Freyssinet. This model paved the way to other subsequent proposals all around the world. Traditional split wedge systems for metallic cables were typically characterized by high tilting angles and small anchoring lengths: this may provoke either the slippage or premature failure if used for FRP cables. Optimized anchorages were developed to meet the peculiar property of composite cables to be orthotropic, with radial direction, subjected to pressure, weaker than the longitudinal one. Such systems, like the bonded anchorage of Meier, are specifically designed pursuing the goal of minimizing the stress magnitude and avoiding the stress peak superposition in the FRP cable. The present work aims at highlighting, starting from historical models, the solutions found in the literature to make traditional anchorages be efficient for FRP cables.