Development of corrosion-free concrete beam–column joint with adequate seismic energy dissipation

The use of Fibre-Reinforced Polymer (FRP) as reinforcement in concrete structures has received much attention owing to its higher resistance to corrosion compared to that of regular steel reinforcement. Since FRP is a brittle material, its use in seismic resisting structural elements has been a concern. FRP RC structures can be made ductile by utilizing a ductile material such as steel at the plastic hinge regions. However, the use of steel negates the corrosion resistance purpose of FRP. On the other hand, Nickel–Titanium (Ni–Ti) shape memory alloy (SMA) is highly resistant to corrosion. It also brings about an added advantage in seismic regions since it has the unique ability to undergo large deformation, but can regain its undeformed shape through stress removal. In this study, a SMA–FRP hybrid RC beam–column joint has been proposed to address not only corrosion resistance, but also seismic related problems. This joint is reinforced with a super-elastic Ni–Ti SMA bar at the plastic hinge regions of the beam and FRP in the other regions of the beam and column. To validate the proposed joint, an experimental investigation has been carried out to develop such a joint and test it under reversed cyclic loading. The results are compared in terms of load–storey drift, moment–rotation and energy dissipation capacity to those of a similar RC beam–column joint specimen reinforced with conventional steel. The SMA–FRP beam–column joint proved to have adequate energy dissipation under earthquake type loading.