Experimental Evaluation of Shape Memory Alloy Retrofitting Effect for Circular Concrete Column Using Ultrasonic Pulse Velocity

The seismic performance of a concrete column retrofitted with an iron-based shape memory alloy (Fe-SMA) was evaluated under cyclic loading. In addition to structural behavior, internal damage was monitored using an ultrasonic pulse velocity test. The round shapes of three reinforced concrete (RC) columns were tested: a non-retrofitted RC column as a control, a carbon fiber-reinforced polymer (CFRP) column, and an Fe-SMA retrofitted column. During the cyclic loading test, the degradation of the column was defined based on the decrease in compressional wave velocities. The experimental results demonstrated a maximum improvement of 175% in seismic performance of the Fe-SMA retrofitted RC column compared with the controlled column. This is primarily owing to the active constraints of the SMA, which were quantified based on ultrasonic velocities. Furthermore, the surface degradation process was identified using external cracks, which were not visible in the CFRP retrofitted RC column.