A MODEL FOR STRESS-STRAIN RELATIONSHIP OF SPIRALLY CONFINED NORMAL AND HIGH-STRENGTH CONCRETE COLUMNS

An analytical model is developed to predict the complete stress-strain relationship of normal and high-strength concrete subject to uniaxial compressive loading and confined by transverse reinforcement. The con finement pressure is assumed to be uniform within the core of the colu mn. The internal force equilibrium, the properties of the materials, a nd the geometry of the section are used to evaluate the pressure. The model utilizes a single fractional equation which satisfies realistic behaviour of the ascending portion, the peak point, and the post-peak descending portion of the stress-strain relationship. The predictions of the model and the available experimental results are compared over a range of concrete strengths. The model shows good predictive capabil ity and is applicable for a wide range of variables such as the diamet er of the circular section, the pitch, diameter and yield stress of th e spiral, and the volumetric ratio of lateral reinforcement.