Reproducible estimations of internal corrosion distribution from surface cracks using MPC-RBSM

Abstract

Rebar corrosion estimation is essential for maintenance of reinforced concrete structures against deterioration. Currently available non-destructive methods of evaluating corrosion do not clearly indicate the internal corrosion condition along the rebar and its effect within the concrete. In prior research, an inverse analysis scheme has been proposed in which the model predictive control (MPC) optimization method is utilized within a rigid body spring model (RBSM) to estimate the corrosion-induced expansion distribution along the rebar from corresponding surface crack width data. In this study, an innovative approach is introduced to verify the precision of MPC-RBSM outcomes and systematically examine the major contributing factors. To facilitate this verification, target cracking is generated by precisely controlling the corrosion expansion within the RBSM framework. In total, three sets of simulations are considered: two cases with varied expansive strain distribution profile along a straight rebar, and third in which a bent rebar arrangement is subject to corrosion. The simulated expansion distribution is compared against the original expansion used to generate the crack width data to validate the reproducibility of the MPC-RBSM results. The inverse analysis results show that the automated expansion scheme in MPC-RBSM successfully reproduces the target surface cracking. In the inverse analysis process, the necessity to account for corrosion distribution is identified. When appropriate corrosion distribution criterion is used to estimate corrosion-induced expansive strain levels along the reinforcement, the results are in good agreement with the assumed corrosion-induced expansive strain profiles (including both uniform and non-uniform profiles). Additionally, simulations of bent rebar corrosion are performed. The results indicate that surface cracking local to the bent region is mainly influenced by corrosion-induced stresses along the straight lengths of the rebar, which complicates the corrosion analysis of bent rebars via this form of inverse analysis.