Cyclic Response of Concrete Bridge Columns Using Superelastic Nitinol and Bendable Concrete

In an attempt to reduce permanent displacements and damage in concrete bridge columns subjected to strong earthquakes, three circular column models incorporating innovative materials in the plastic hinge zone were tested under slow cyclic loading to failure. The first model, round steel conventional concrete (RSC), used conventional concrete and steel reinforcement in the plastic hinge. The other two models incorporated superelastic shape memory alloy (SMA) longitudinal reinforcement, one (round NiTi conventional concrete [RNC]) with conventional concrete and the other (round NiTi engineered cementitious composites [RNE]) using engineered cementitious composites (ECC). The average ratio of residual to maximum displacement in RNE was 1/6 of that of RSC and 1/2 of that of RNC, indicating substantial benefits of using the combination of SMA and ECC. RNE experienced the least damage and the highest drift capacity among the three columns. The residual drift in RNC was also small, but the damage was significant. Analytical studies using a computer program led to reasonable estimates of forces, residual drifts, and the cyclic response. [PUBLICATION ABSTRACT]