Seismic performance of RC pier columns with shape memory alloy fibers-reinforced engineered cementitious composite (SMAF-ECC) wrapped plastic hinge regions

In seismic events, the ductility shortage of RC pier columns, rooted in insufficient deformation capacity of plastic hinge zones, remains a pivotal factor triggering structural failure. Superelastic Shape Memory Alloy Fibers-Reinforced Engineered Cementitious Composites (SMAF-ECC), a novel composite, features strain hardening, self-recovery, and high energy dissipation. Applying SMAF-ECC to plastic hinge zones of pier columns effectively enhances ductility and seismic performance, enabling rapid post-seismic repair. This paper proposes a novel RC pier with SMAF-ECC wrapped plastic hinge zones. One conventional RC pier and three SMAF-ECC wrapped pier columns (SMAF contents: 0 %, 0.5 %, 0.75 %) were tested under low-cycle reciprocating loads. The test results showed that SMAF-ECC/RC pier column exhibited outstanding performance in terms of energy dissipation capacity, self-recovery capacity, and possessed good bearing capacity. At 0.50 % SMAF volume content, compared with conventional RC pier column, the energy consumption, displacement recovery, peak load, and yield load of SMAF-ECC/RC pier column are increased by 50.24 %, 71.04 %, 14.25 %, and 21.08 %, respectively. Moreover, the ductility coefficient reaches up to 4.21. Compared with ECC/RC pier column, the energy consumption, displacement recovery, peak load, and yield load of SMAF-ECC/RC pier column are increased by 36.01 %, 38.68 %, 9.69 %, and 13.51 %, respectively. Furthermore, the evolution of bearing capacity with SMAF content was found to be governed by the competition between the tensile enhancement effect of SMAF and a sectional stiffness counter effect, explaining the optimal performance at 0.5 % content. Finally, a mechanism-informed theoretical model for the horizontal bearing capacity of pier columns was established, explicitly considering the tensile contribution of SMAF-ECC. The calculated results agree well with the experimental data, with a correlation coefficient of 0.9299 and an average relative error of 5.77 %, providing a novel technical approach and theoretical basis for seismic enhancement of SMAF-ECC/RC pier columns.