The Effect of Combined Environmental and Service Loads on Bridge Piers Using Non-Linear Finite Element Analysis

Abstract

Corrosion of reinforcing steel has been identified as the leading cause of deterioration in North America's reinforced concrete (RC) infrastructure. Global warming accelerates both reinforcement corrosion initiation and propagation. Furthermore, global warming could lead to higher freeze-thaw cycle (FTC) frequency in cold regions, affecting the structural performance and service life of aging RC infrastructures. There is a scarcity of numerical research on the effects of FTCs or the combined effects of corrosion and FTCs on the structural performance of real-scale columns/piers. The present study develops a numerical framework to analyze deteriorated RC bridge piers by adopting comprehensive corrosion and frost damage models from the literature. Comparisons with available test data from the literature assess the adopted damage models. Corroded columns and frost-damaged beams from the literature were selected and simulated by incorporating the adopted damage models. A stage-based damage framework during the service life of a bridge is proposed, and it is illustrated for a bridge located in Montreal, Canada. First, the detrimental effects of corrosion on the pier’s structural performance are studied. The stage-based analysis is then conducted to study the combined effects of corrosion and freeze-thaw cycles over 60 years of the bridge’s service life. The present study assumes three combined corrosion-frost damage levels. At level 1, it is assumed that all the reinforcement, core concrete, and the bond-slip response in the splashing zone are affected by stage 1 corrosion, and the cover concrete is degraded under 22 FTCs after ten years. At level 2, the steel rebars and the bond-slip response are affected by stage 2 corrosion, and the cover concrete and corrosion-induced damaged core concrete are assumed to degrade under 113 FTCs after 40 years. Level 3, the worst-case scenario, corresponds to extensive corrosion of rebars (stage 3), spalling of the cover concrete, and frost-induced damage penetration towards the core concrete (splashing zone) after 60 years of service. Three-dimensional nonlinear finite element analyses using the finite element program, DIANA, are conducted to evaluate the structural performance of the RC bridge pier under service loading and subjected to corrosion alone and to corrosion combined with FTCs after ten, forty, and sixty years. From analysis of the numerical results, it is observed that a significant decrease in the pier’s ultimate axial and flexural capacity, rigidity, and deformability shows the importance of periodic inspection and investigation in the first ten years and rehabilitation planning in the first 40 years of the bridge’s service life. Comparing the structural performance of the pier deteriorated by frost damage only and a combination of corrosion and frost damage shows the intensifying effects of corrosion in the degradation process. The present modelling framework can also successfully capture the failure pattern of the damaged RC pier. A simplified sectional nonlinear analysis is also conducted to evaluate the validity of the proposed quantitative evaluation approach and propose an efficient assessment approach to approximately estimate the remaining capacity of aging piers.