Steel jacketing retrofitting of reinforced concrete half-joint T-beams: Experimental tests and refined numerical investigation

This study combines numerical and experimental investigation for the development of a steel jacketing retrofitting system for half-joint beams (also known as dapped-end beams or Gerber saddles) addressing corrosion-induced loss of load-bearing capacity. The proposed system employs steel plates with prestressed bolts at the sides of the web to bypass the stress transfer in the damaged area of the saddle. The reference experimental tests included two half joint T-beam specimens with different reinforcement layouts, tested in two static configurations. To complement the experimental tests, high-fidelity 3D finite element models were developed using the STKO platform for OpenSees and calibrated against experimental results to ensure reliable replication. Additional high-fidelity models allowed the investigation to be extended to extra configurations not covered experimentally, providing insights into the influence of flange-web interaction and potential brittle failure modes. A modified retrofitting configuration incorporating rigid flange connections via post-installed anchors is proposed and evaluated. Results indicate that both the original and improved systems can enhance strength and ductility of damaged joints, with the modified solution delivering higher performance.