Lateral Cyclic Behavior of Reinforced Concrete Columns Retrofitted with Shape Memory Spirals and FRP Wraps

摘要

This experimental work focuses on enhancing the lateral cyclic behavior of RC columns by using an innovative active-confinement technique. The thermally triggered recovery stress of prestrained shape memory alloy (SMA) spirals is used to apply the active-confinement pressure. Four 1/3-scale RC columns, three of which are retrofitted with different schemes, are tested under quasi-static lateral cyclic loading. The plastic hinge region of the first retrofitted column is actively confined using the new SMA spirals, whereas for the second column, traditional passive confinement is applied by using a glass fiber-reinforced polymer (GFRP)/epoxy jacket. The third column is retrofitted by using a hybrid confinement approach, which is applied by using SMA spirals and GFRP jacket simultaneously at the plastic hinge zone. The confinement pressure of the three retrofitted columns is designed to be the same. The results show a significant increase in the flexural ductility capacity and energy dissipation capability of the columns retrofitted with SMA spirals compared with those of the as-built column and the GFRP-retrofitted column. SMA spirals also show an outstanding ability to mitigate the damage sustained by the columns under extreme lateral drifts.