Performance of nonseismically designed RC beam column joints strengthened by various schemes subjected to seismic loads - A review

This paper reports on effective strengthening of nonseismically designed reinforced concrete beam-column joints subjected to seismic loading. The reinforced concrete buildings designed during early 1950's through 1970's, however, functioning today require special treatment when exposed to seismic forces. Many components of these buildings lack sufficient strength and ductility to wimstand the earthquake forces. Improper detailing of reinforcement, inadequate anchorage length, and insufficient strength are some deficiencies encountered in the junction of framing beams and contains, which plays an important role on the gtobal response of structures. Different strengthening methods such as jacketing, fiber wrapping with proper anchorage, and use of haunch elements for altering the joint shear stress are used. Fiber reinforced polymers (FRP) are proved to be beneficial for retrofitting, however, with potential difficulties. The Important design parameters such as the joint shear strength and energy dissipation capacity have been discussed vis-a-vis in various strengthening schemes. The mechanics of joints altered by the addition of haunch elements have been found to reduce the distress in the joints significantly. Numerical investigations have been made to study the effect of haunch elements on the reduction of shear forces and the bending moments in the framing members and in the joint region. The highest values of reduction in the joint shear force and the bending moment are found for a particular combination of location and inclination of the haunch elements with the framing members.