Proactive Enhancement on Axial Compression Performance of Concrete Columns Employing Fe-SMA

This study experimentally investigates the axial performance of concrete columns confined with Fe-SMA (iron-based shape memory alloy) strips. An integrated active reinforcement technique is developed, incorporating an anchorage system and a thermal activation procedure to reliably apply lateral confinement stress. Axial compression tests are conducted on specimens with various confinement configurations by adjusting the number of Fe-SMA strips, prestrain levels, activation conditions, and the presence of stirrups. The results demonstrate substantial enhancements in load capacity, ductility, and failure control. Parametric analyses identify key confinement interactions, including the diminishing marginal effect, the transition between active and passive confinement, and the synergy between Fe-SMA and stirrups. The relative contributions of each confinement mechanism are quantitatively assessed through Pearson correlation and random forest regression. A unified analytical model is proposed to predict the stress–strain response by integrating multiple confinement components. The findings offer both theoretical insights and practical guidance for the structural application of Fe-SMA in reinforcing vertical concrete members.