Study and application of smart monitoring on compressed structures based on CFRP self-sensing

A novel approach to structural health monitoring of compressed structures leveraging the intelligent properties of carbon fiber Reinforced Polymer (CFRP) was investigated. Smart CFRP strips were attached to the side surfaces of the axially compressed concrete column at various angles, and the electrical resistance of these strips under both monotonic and cyclic compression at different off-axial angles were analyzed. The findings reveal that the resistance of smart CFRP strips throughout the entire monotonic loading process correlates with the changes of the monitored structure, undergoing initial gradual changes, rapid changes at middle stage, and a sharp change upon the structural failure. The resistance changes partly reverse after failure. Under cyclic loading, the resistance shows periodic variations, with the resistance changes primarily being reversible, except for a small amount of irreversible resistance that occurs during the first loading cycle. Additionally, the off-axial angle, $ \mathrm{\;\beta } $, significantly influences the resistance response. At $ \mathrm{\;\beta } $=0° and $ \mathrm{\;\beta } $=90°, the smart strips exhibit negative and positive piezoresistive effects, respectively; while at $ \mathrm{\;\beta } $=45°, they display various piezoresistive effects in different phases, with a smaller change in resistance. The practical application results confirm the applicability and efficiency of the smart CFRP strips in structural monitoring.