In this contribution, as part of a more extensive research program on seismic retrofit solutions forreinforced concrete buildings, the effects of bi-directional loading on the assessment and design of theretrofit intervention using FRP composite materials will be discussed. Based on experimentalevidences on the performance of exterior 3D (corner) under-designed beam-column joints, the limitsand drawbacks of standard assessment methodologies when evaluate the hierarchy of strength andexpected sequence of events prior to define the retrofit intervention, will be discussed. In addition, thepreliminary results of an on-going experimental campaign to further investigate and address this issuewill be presented, based on the quasi-static tests under bi-directional loading on two 3D exterior(corner) joint specimens, comprising of a pre-1970s as-built specimen (benchmark) and a “minimum”retrofitted configuration using GFRP sheets. The feasibility and efficiency of the adopted retrofitstrategy and solution, aiming at controlling the hierarchy of strength within the beam-column jointsystem by protecting the panel zone and relocating the plastic hinge in the beam, will be discussed.Considerations and suggestions on the additional design criteria to account for the actual 3-Dresponse under bi-directional loading will be also given.
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