Seismic performance of precast shape memory alloy confined bridge piers

The use of precast concrete (PC) is gaining attention in the bridge industry due to its inherent advantages, such as reduced traffic disruption, the safety of both workers and the traveling public, and construction efficiency. As the connection location of precast bridge piers often coincides with the plastic hinge regions, using precast piers in high seismic zones is challenging. Furthermore, seismic design specifications impose strict requirements for transverse reinforcement in these regions for better energy dissipation. Combined with the typically high longitudinal reinforcement ratio in bridge piers, high transverse reinforcement requirement leads to steel congestion in the plastic hinge regions, which significantly affects the construction quality. The use of active confinement (transverse prestressing) at the plastic hinge region can potentially help with the steel congestion issue. However, the application of active confinement using conventional materials has proven to be problematic. Shape memory alloys (SMAs) with their unique thermal prestressing capability offer an effective technique for applying active confinement. This study presents a new solution for steel congestion in PC bridge piers using SMA spirals. The proposed design significantly reduces steel congestion by reducing transverse reinforcement in the concrete core of plastic hinge regions without increasing the member size and stiffness, as well as seismic demand. The performance of the proposed SMA-confined pier is investigated numerically through a parametric study. The results prove the feasibility of the proposed concept for use in high seismic regions.