Empirical macro-model for flexure-controlled reinforced concrete columns with plain bars

In this study, an empirical approach for the nonlinear modelling of flexure-controlled Reinforced Concrete (RC) columns with plain bars is developed. A database of tests on RC columns with plain bars is collected, with varying axial load, material properties, geometry, and longitudinal and transverse reinforcement ratio. The response is analysed in terms of base moment-chord rotation relationship, identifying characteristic points corresponding to yielding, maximum, “ultimate”, and zero resistance conditions. The hysteretic response is analysed, too, evaluating the degradation of unloading and reloading stiffness with imposed inelastic displacement and the “pinching” behaviour. Empirical formulations are developed, analysing the dependence of the investigated parameters on selected potential predictors. The effectiveness of the proposed formulations is evaluated, comparing the modelled response and the predicted deformation capacity with the results obtained applying modelling approaches and capacity models proposed by literature studies and technical codes.