Various strengthening schemes that can be used for the strengthening of beam-column joints are based on providing aditional shear reinforcement to the joint core. These strengthening schemes include FRP wraping, concrete jacketing, steel plating etc. Although these strengthening methods are quite effective as shown through several laboratory tests, their use in practice is often met with problems of accessibility of the sides of the joint core due to the beams and slabs framing into the joint. This severely affects the effectiveness of the strengthening used for the joints.
Within the framework of my PhD, I worked on development of fully fastened haunch retrofit solution (FFHRS) for strengthening of beam-column joints of non-seismically designed structures. The principle of this retrofit solution is not to provide additional shear reinforcement but to protect the joint by reducing the shear force coming on to the joint core. The strengthening solution involves in providing steel diagonal elements (known as haunch elements) at the interface of the beam and the column and connecting it to the frame members using post-installed anchors. The use of post-installed anchors render this solution low-invasiveness and the solution is equally effective even if all the sides of the joint are not accessible. The efficiency of this retrofit solution largely depends on the performance of the anchorage used to connect the haunch elements to the frame members. If the anchorage serves its function well, the retrofit solution leads to the re-distribution of forces around the joint core and with proper design, result in changing the failure mode from brittle joint shear to ductile beam flexure. The re-distribution of the forces leads to reduction in bending moment at the face of the joint but also leads to an increase in the shear force in the frame members (beams and columns). Therefore, the design of the retrofit solution must consider the sufficiency of the shear capacity of the frame members.