Bi-axially loaded RC beam-column joints and haunch retrofit

In this study, seismic bi-axially loaded RC beam-column joints are investigated. An experimental campaign on shear-critical corner joints is presented, including two as-built specimens and one retrofitted using fully-fastened-haunches (FFHR). Bi-axial tests adopted hexagonal protocol which is essentially to apply load in one direction double with respect to the other. Results obtained for as-built condition were included in a database of corner joints tested bi-axially and discussed in the light of the impact of bi-axial load on joint's shear strength. Further, non-linear finite elements were employed to thoroughly evaluate the bi-axial response. Haunch retrofit was capable to reduce both shear stresses and distortion at joint. Experimentally-derived internal forces were used to validate three-dimensional Strut-and-Tie model of the joints. Such design tool is recommended for practice cases adopting FFHR.