Deformation capacity of FRP retrofitted reinforced concrete columns with corroded reinforcing bars

FRP retrofitting is an effective way to promote the degraded seismic capacity of reinforced concrete (RC) columns with corroded reinforcing bars. It is important to evaluate whether the performance of a corroded RC column meets the requirement of safety after FRP retrofitting. However, there is little available guidance for evaluating the deformation capacity of FRP retrofitted corroded columns. In this study, the test data of 63 FRP retrofitted corroded columns and 17 FRP retrofitted uncorroded columns under repeated cyclic loads are collected to establish a database. For each specimen, the rotation angles at yielding and ultimate states are determined from the backbone curve. The empirical prediction models are then developed for the yield and ultimate rotation angles of FRP retrofitted corroded columns, which include two parts: 1) the predicted rotation angle for the FRP retrofitted uncorroded RC column, and 2) a Corrosion Influence Factor (CIF) defined as the ratio between the rotation angles of the FRP retrofitted corroded columns to that of the FRP retrofitted uncorroded ones. The former part is represented using the available empirical prediction models, whereas the latter part is represented using the multi-linear relationships through stepwise regression with a backward elimination procedure. Through comparing with the experimental data, the developed empirical prediction models for the yield and ultimate rotation angles of FRP retrofitted corroded columns provide sufficient accuracy. Finally, the parameter "a" is determined in corresponding to different target probability of exceedance, which is required by the ASCE 41-compliant force versus displacement relation for FRP retrofitted corroded RC columns.