Stress–Strain Behaviour and Constitutive Modelling of Unconfined and Confined Ultra-High-Performance Concrete (UHPC)

Ultra-high-performance concrete (UHPC) is valued for its exceptional compressive and tensile strength, yet its use remains limited to small-scale applications due to gaps in understanding its behaviour in larger structures, particularly axially loaded reinforced concrete (RC) columns. This thesis addresses these gaps by developing unified constitutive models for both unconfined and confined UHPC, calibrated to widely-used fibre types. Through comprehensive experimental investigations and multi-scale mechanical characterisations, the models offer a more accurate representation of fibre contributions and interactions with transverse reinforcement, enabling better predictions of stress–strain behaviour and facilitating more effective design and analysis of UHPC structural members.