A Macro Model for Simulating Strength Degradation in Shear-Critical RC Columns

Shear failure followed by axial collapse in reinforced concrete (RC) columns with insufficient transverse reinforcement represens a critical structural failure mode.Conventional analytical models often fail to accurately capture flexural-shear-axial interaction effects, whereas detailed finite element methods entail substantial computational cost.This study proposes a novel macro-element model that integrates material-level accuracy with the computational efficiency of line elements.The column is discretized into three elements along the longitudinal axis.Plate elements are formulated using a four-node plane-stress model incorporating the modified compression field theory (MCFT) to represent biaxial stress states and concrete compression softening.A double-nested iteration scheme is developed to satisfy equilibrium conditions.Validation against experimental data demonstrates that the proposed model accurately reproduces post-peak strength degradation and shear failure behavior, thereby addressing the key limitations of conventional fiber-based models.