Reduced Cross-Section Modeling of Pitting-Corroded RC Beams: Experimental Validation and Sensitivity to Cohesive Parameters

This study presents a three-dimensional finite element analysis of bond degradation between corroded steel reinforcement and concrete in reinforced concrete (RC) beams subjected to monotonic loading. A reduced cross-section method based on a uniform reduction of the bar diameter is adopted to account for the loss of steel area due to corrosion. The equivalent solid diameters of the corroded bars are derived from the gravimetric mass loss (η) of each bar, using the actual volumes of as-manufactured ribbed bars (16.37 mm for Y16, 12.38 mm for Y12, 10.41 mm for Y10). The concrete damage plasticity (CDP) model is used to capture cracking and crushing of concrete while bond behavior is modeled using a cohesive zone approach. Five corrosion levels (3.40% to 7.37%) are investigated. A comprehensive parametric study reveals that the response is totally insensitive to the cohesive parameters over a wide range (Knn = 100–100,000 N/mm³, τmax = 2.3–8.5 MPa, Gs = 4.0–17 N/mm), confirming that the loss of steel cross-section is the primary mechanism controlling the residual capacity. The numerical results are validated against experimental data for three reinforcement configurations (1Y16, 2Y12, 3Y10). Results highlighted that the reduced-section method successfully captures the transition from ductile to brittle failure, demonstrating its potential as a simple, computationally efficient, and physically consistent tool for predicting the residual bond capacity of corroded RC beams.