Drift limit state predictions of rectangular reinforced concrete columns with superelastic shape memory alloy rebars

Abstract

This study derives empirical drift limit state expressions for rectangular concrete columns reinforced with nickel–titanium shape memory alloy (SMA) bars using numerical simulation results obtained from well-calibrated nonlinear finite element models. A parametric study is conducted to examine the effects of various design parameters, such as the axial load ratio, section information, and material properties of concrete and SMA on the drift limit states of the columns. For each limit state (LS), a multivariate stepwise regression analysis was performed. An expression was derived to estimate the associated drift capacity of the SMA-reinforced concrete columns. In addition, the precondition for the SMA-reinforced concrete columns to ensure ductile behavior was investigated. It turned out that the axial load and the amount of transverse reinforcement are the most influential parameters on the ductility of the columns. Finally, nonlinear static and dynamic analyses were conducted for an SMA-reinforced concrete building frame to demonstrate the application of the proposed drift LSs. Both analysis results revealed that the building model tends to experience core crushing or loss of lateral load capacity prior to SMA failure.