In-Plane Quasi-Static Cyclic Testing of Rc Frames Retrofitted With Rigid/Dissipating Steel Haunches

This research assessed the reliability of haunch retrofitting technique for seismic upgrade of critically damaged frames. Two 1:3 reduced scale two-story RC frames were taken under considered, which were tested previously till the near collapse state. The haunches are employed to strengthen the joint shear strength of the badly damaged joints, which are indicative of old, non-seismic, or defective joints. Damaged concrete was replaced with new high-strength concrete, and haunch-retrofitting technique was adopted to strengthen beam-column connections, in order to avoid shear hinging at joints under lateral loads. The retrofitted frames were tested through quasi-static cyclic loads in a displacement-control condition for multiple-levels of roof drifts. In order to assess the following seismic response factors: stiffness, strength, ductility, and response modification factors—lateral force-displacement capacity curves were created and examined. Hysteretic responses of tested models were analyzed to quantify hysteretic damping. The seismic performance assessment of the retrofitted frames was conducted utilizing a code-based static force approach in multiple seismic zones. The rigid haunches contributed to the over strength factor while the dissipating haunch has major contribution in energy dissipation of the retrofitted frames.