Uniaxial compressive behavior of concrete column actively confined with internal Fe-SMA spirals

This paper presents experimental and analytical study results to evaluate the uniaxial compression behavior of concrete columns actively confined with Fe-based shape memory alloy (Fe-SMA) spirals. For the study A total of 16 concrete columns were fabricated for the study. Ten of the columns were actively confined by Fe-SMA spirals through electrical resistance heating, while four columns were passively confined by deactivated Fe-SMA spirals. Finally, the remaining two columns were unconfined specimens without lateral reinforcement. The experimental variables included the pitch of the Fe-SMA spiral, confinement type, and heating temperature. The Active confinement due to activation of the Fe-SMA spiral resulted in improved ductility of the confined concrete columns compared to passive confinement. The effects of activation status and heating temperature were more prominently observed in specimens with smaller spiral pitches and lower concrete compressive strength. Particularly, the compressive strength of columns actively confined with a 30 mm pitch spiral was enhanced by over 100% compared to unconfined concrete. Furthermore, an analytical stress-strain model for concrete actively confined with Fe-SMA spirals was proposed in this study. The proposed model accurately predicted the experimental results of columns confined with external SMA wires reported by other researchers.