Improved Damage Model of RC Columns Accounting for the Influence of Variable Axial Load

The aim of this study is to address the limitations of fixed parameters and poor adaptability in traditional damage models for damage assessment of reinforced concrete (RC) columns under variable axial load. An improved damage model considering the influence of variable axial load was proposed herein. Based on quasi−static tests of RC columns under variable axial load, a fiber finite element model was established, and its reliability was verified using experimental data. The limitations of classical damage models were systematically analyzed, and the quantitative relationship between core parameters and axial load ratio was derived via numerical simulation of multi−level axial load ratio working conditions, on the basis of which the traditional model was modified. The applicability of the improved model was evaluated through full factorial combination working conditions, and the quantitative correlation among damage indices, stiffness degradation, and load−bearing capacity degradation was established. The results indicate that the improved model addresses the limitation of fixed parameters of traditional models, maintains stable calculation accuracy for circular RC columns under the investigated ranges of axial load ratio, shear−span ratio, and reinforcement ratio, and enables quantitative prediction of mechanical properties based on the damage index.