A computational framework based on COMSOL Multiphysics and OpenSEES for assessing the time-dependent cyclic response of RC bridge columns subjected to chloride-induced corrosion

Long-term performance analysis of reinforced concrete (RC) infrastructures subjected to deterioration phenomena induced by the exposure to corrosive environments is a truly challenging task. Nonetheless, it is essential for designing new structures as well as for predicting the residual life of existing constructions or for planning suitable maintenance interventions. Within this framework, chloride-induced corrosion deserves special attention because of its serious consequences on the reliability of RC members. Therefore, the present work illustrates a comprehensive computational framework meant at supporting the long-term forecasting of the structural performances of RC bridge columns exposed to chlorides. Specifically, chloride ingress in the cross-section of the column is accurately simulated considering the concurrent effects due to temperature, humidity, aging and corrosion-induced cover cracking. Once the partial differential equations governing such problem are solved through the finite element method within COMSOL Multiphysics, the loss of reinforcement steel bars cross-section is calculated based on the estimated corrosion current density. On the other hand, the nonlinear cyclic response of the RC bridge column under corrosion is determined within OpenSEES by discretizing its cross-sections into several unidirectional fibers. The nonlinear modeling of the corroded longitudinal rebars exploits a novel proposal for the estimation of the ultimate strain in tension. It also accounts for buckling of the longitudinal reinforcement under compression with a time-dependent variable buckling length due to the evolution of corrosion into transverse reinforcement. Moreover, a simple, yet effective, way is proposed to parametrize the corrosion pattern by combining generalized and localized corrosion (Fig. 1), in such a way to facilitate the simulation of different scenarios. As regards the localized corrosion, the proposed parametrization allows to reflect number, position, and morphology of the pits. The results obtained for a real case-study are finally discussed to explain the role of the longitudinal rebars buckling on the time-variation of capacity and displacement ductility.