Simulation of longitudinal reinforcing steel bar fracture in reinforced concrete walls

Structural systems in buildings are designed to manage seismic impacts through ductile inelastic responses, allowing significant cyclic deformations without substantial loss of load-bearing capacity. Reinforced concrete wall structures dissipate energy mainly through the cyclic yielding of steel reinforcement bars. However, repeated inelastic cycles accumulate damage, increasing the risk of reinforcing bar fracture due to low-cycle fatigue. This study introduces a novel modeling methodology that simulates the fracture of reinforcement in such scenarios, which traditional models often neglect or simplify by imposing maximum strain capacities on reinforcing steel. Our approach integrates a model that accounts for cumulative damage and fracture due to low-cycle fatigue using the newly implemented reinforcement ductile fracture model (RDFM) in OpenSees software. This allows for a detailed representation of cumulative damage and bar fractures, enhancing the predictive accuracy of the cyclic behavior and subsequent strength and stiffness degradation of reinforced concrete walls. Validated against 23 selected reinforced concrete wall cyclic tests, the methodology effectively captures the impact of low-cycle fatigue on concrete walls, contributing to more accurate post-earthquake building assessments. Furthermore, the study proposes a novel calibration for the Equivalent Slenderness Factor (\(\Psi \)) tailored to wall conditions. This research advances our understanding of structural behavior under seismic loads, offering a robust tool for enhancing seismic performance assessments and influencing future design protocols.