Influence of embedded through section connectors on the behavior of a new strengthening technique for concrete structures

An innovative technique is being developed for the structural rehabilitation of Reinforced Concrete (RC) structures. In particular, the infill walls of RC framed structures are often identified as non-structural elements, but currently are considered with an important role in the structural behavior because they participate to the in-plane strength and stiffness of the frames and they can give very dangerous crashes out-of-plane. In this paper a strengthening technique aimed to repair infill walls is proposed. It is based on the application of outer thin layers of ultra-high ductile fiber reinforced mortar (UHDFRM) applied according to the shotcrete technique, including the use of embedded through section (ETS) connectors. This strengthening system can exhibit a high strength and ductile behavior, increase the load carrying capacity, energy absorption and dissipation capacities, and ultimately improve the structural response of RC structures when submitted to loading conditions typical of seismic events. An experimental program was outlined in order to assess the contribution of different types of ETS connectors on the behavior of the strengthening system. The experimental program comprised the performance of push-out tests on samples representative of the structural strengthening solution, namely low strength concrete samples. The experimental results are discussed in detail in order to highlight the effectiveness of the various types of ETS connectors tested.