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.