Evaluation of the Effect of Reinforcement Corrosion on the Axial and Flexural Performance of RC Columns
Creators: name: Dabas, Maha
Publisher: name: Université d'Ottawa / University of Ottawa
Year: 2022
Subjects: Reinforcement corrosion
RC columns
Axial and flexural response
Finite element modelling
Experimental testing
Analytical approach

description: The heavy use of de-icing salts in the winter to accommodate heavy traffic has been the most detrimental cause of chloride-induced corrosion in Canadian reinforced concrete (RC) bridge infrastructure. In addition, the rise of greenhouse emissions and subsequent increase in the mean surface temperature have increased the potential risk of carbonation-induced corrosion. It is believed that the synergistic effect of multiple deteriorating mechanisms will accelerate the incidence of reinforcement corrosion in Canadian infrastructure. Over time, premature deterioration of RC bridges due to reinforcement corrosion leads to concrete cover cracking and spalling, loss of bond between reinforcement and concrete, and reduction in the structural capacity and ductility of the structure. There is limited research work that has examined the effect of corrosion on the structural performance of RC columns. This research has evaluated the axial and flexural capacity of corroded RC columns exposed to different levels and patterns of reinforcement corrosion. An experimental testing campaign of ten RC columns was conducted in two stages. During the first stage, eight columns were subjected to an accelerated corrosion regime by impressing a constant current for 137 days. In the second stage, all ten columns were subjected to an axial quasi-static load until failure. Five columns were loaded concentrically, while the remaining five were loaded eccentrically. The structural performance (residual strength, ductility, resilience, stiffness, toughness and failure mode) of the columns were analyzed from load-displacement curves of the entire and mid-span length of the columns. The experimental results show that corrosion of the ties directly affects the column's post-peak response even at low corrosion levels. Columns with corroded ties had a brittle failure, and the residual ductility and toughness were significantly reduced. On the other hand, longitudinal reinforcement corrosion primarily affects the residual strength of the columns, which is prominent at a medium level of corrosion. At high levels of both longitudinal and transverse reinforcement corrosion, the residual strength, ductility, and axial stiffness are significantly reduced. This is accompanied by a significant deterioration of the cover and local buckling of the longitudinal rebars, which is attributed to a significant reduction in the confinement pressure of the core concrete. A three-dimensional non-linear finite element model (3D-NLFEM) of the columns was developed using the finite element package DIANA (v.10.4) and validated with the experimental results. The effect of reinforcement corrosion on the structural response of columns was modelled as a change in the mechanical and geometrical properties of concrete and steel materials. This was achieved by integrating constitutive and deteriorating models into the 3D-NLFEM. The model accounts for the bond-slip behaviour between longitudinal bars and concrete (for eccentrically loaded columns), the confinement of the concrete core and strength reduction of the concrete cover, and the buckling potential of longitudinal reinforcement. The validated model was used to conduct a parametric analysis to investigate the effect of several influencing variables such as damage level and patterns and to explore scenarios beyond those tested in a laboratory setting. Finally, an analytical model based on sectional analysis was developed and compared with both the experimental and FEM results. The proposed analytical approach was developed by integrating deteriorating models and incorporating data collected from field investigation. Based on this evaluation, a practical analytical approach is proposed to estimate the nominal residual capacity of corroded columns considering the reduction in confinement effects, bond loss and potential buckling. The results from the experimental, numerical, and analytical studies correlate well. This work's outcome will contribute to a better understanding of the axial and flexural performance in terms of the ultimate capacity, post peak response and failure mode of RC columns affected by the reinforcement corrosion and static loading. Moreover, it provides a simplified analytical tool for practicing engineers to predict the axial and flexural capacity of deteriorated bridges vulnerable to reinforcement corrosion and increased traffic volume.