Seismic performance of deficient RC frames retrofitted with SMA-reinforced ECC column jacketing

This paper presents the utilization of shape-memory alloys (SMAs) and engineered cementitious composites (ECC) as an alternative to carbon steel and concrete, respectively, for the seismic retrofitting of deficient reinforced concrete (RC) moment-resisting frames using the technique of column jacketing. An open ground story (OGS) of a three-story RC frame was retrofitted with four different materials combination; conventional carbon steel rebar-concrete jacketing (S1), ECC-carbon steel rebar jacketing (S2), SMA rebar-concrete jacketing (S3), and SMA rebar-ECC jacketing (S4), and an un-retrofitted frame (control frame, S5). Nonlinear static time history analyses were performed using a finite element program, and the results for the un-retrofitted and various retrofitted frames were assessed in terms of hysteretic response force-displacement curves, energy dissipation, performance criteria, and lateral force-deformation capacity curves. Results indicated that using SMA rebar and ECC concrete collectively as jacketing materials offer maximum benefits such as an increase in lateral resistance, reduction in residual deformation through the self-recovering ability of SMA, as well as provide adequate energy dissipation capacity. Furthermore, dynamic time history analyses were performed on two-story portal frames and inter-story drift demands were identified for the un-retrofitted and various retrofitted frames. SMA-reinforced retrofitted frames slightly increased inter-story drifts due to the lower modulus of elasticity of SMA, resulting in lower stiffness of the frames. In order to keep the inter-story drift demand within an acceptable limit, the stiffness of the SMA frames needs to be increased.