Hysteretic model for corroded reinforced concrete columns retrofitted with FRP

A hysteresis model was developed for fiber reinforced polymer (FRP)-retrofitted reinforced concrete (RC) columns with corroded reinforcing bars. The test data of 49 FRP-retrofitted corroded columns and 19 intact columns (with no corrosion or FRP wraps) under repeat-cyclic loading were collected to establish a database. A polygonal model was adopted to simulate the hysteretic behavior of FRP-retrofitted corroded columns. This was determined using backbone and cyclic parameters. For the backbone parameters, a hybrid influence factor (HIF) was introduced to incorporate the coupling effects of corrosion and FRP retrofitting. A suite of empirical equations was developed using multivariate linear regression analysis to predict the HIFs of each backbone parameter in association with the corrosion rate and important column design parameters. Moreover, an empirical relationship was developed to determine the cyclic parameters of the hysteretic model using a regression analysis. The predicted hysteretic curves were compared with the experimental results, demonstrating sufficient accuracy for both intra- and extra-database tests. Finally, the developed hysteretic model was used to establish a macro-type structural model for the FRP-retrofitted corroded RC frames. This benefitted the analysis of structural collapse under earthquakes, and the effects of the corrosion rate and FRP retrofitting schemes on the seismic collapse capacity of RC frames were examined.