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

Abstract

This study investigates the effectiveness of reinforced concrete bridge columns with superelastic shape memory alloy (SMA) reinforcement and engineered cementitious composites (ECC) in plastic hinges in reducing permanent residual column displacements and damage due to 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 SMA longitudinal reinforcement: one (round Nitinol conventional concrete (RNC)) and the other (round Nitinol engineering cementitious composites (RNE)). The average ratio of residual to maximum displacement in RNE was one-sixth of that of RSC and one-half 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. Results from analytical studies using a computer program showed good correlation with the experimental data.