Non-linear shear analysis of reinforced concrete columns by fixed-angle theory

This paper predicts the shear response of reinforced concrete columns with bending moment and axial load by a truss model based on the fixed-angle theory. The proposed model has a simple formulation by using average constitutive relationships and can also estimate the shear contribution of concrete at crack surfaces by fixing crack directions. Using the constitutive laws of principal applied stress direction, the model is applicable to reinforced concrete columns that have a large difference in the amounts of longitudinal and transverse reinforcements. In addition, the effects of bending moment and axial force acting on the shear-critical columns are considered in the proposed formulation. To verify the applicability of the proposed formulation to the shear behaviour of reinforced concrete columns, nine reinforced concrete columns with various shear span-to-depth ratios and axial force ratios were cast and tested. Additionally, the experimentally observed shear strengths of 47 columns in the literature were compared with predicted shear strengths obtained from the proposed model and existing models.