Seismic Repair and Retrofit of RC Beam–Column Joints Using Stiffened Steel Plates

Abstract

Evidence from past earthquakes has shown that during significant events, there are always a number of structures that stay stable but experience different forms of damage in their members. Among these members, beam–column joints in the moment frames are more susceptible to seismic loading and may experience different modes of failure. In this paper, stiffened steel plates are used to repair and retrofit a full-scale damaged RC beam–column joint. The retrofit method is based on joint enlargement. A full-scale external beam–column joint is designed and constructed as an ordinary moment resisting frame based on ACI 318M-11 provisions. The structure is then subjected to progressive quasi-static cyclic loading to failure. The damaged joint is then repaired to its former configuration using pressurized epoxy resin and retrofitted by stiffened steel plates. The repaired and retrofitted joint is then subjected to the same cyclic loading protocol to failure. Seismic performance parameters such as strength, stiffness, ductility and energy dissipation capacity of the original joint and the repaired and retrofitted joint are then extracted from their capacity backbone curves and compared. Results show that the proposed repair and retrofit technique not only regenerated the original capacity but also increased capacity and improved the joint performance by relocating the plastic hinge beyond the repaired region.