Stress–strain model for normal- and light-weight concretes under uniaxial and triaxial compression

• Two experimental databases of confined and unconfined concretes are reported.
• Parameters defining pre-peak, peak and post-peak conditions of concretes were established.
• A unified stress–strain model for confined and unconfined concretes is presented.
• The model is applicable to concrete specimens with various dimensions, densities and strengths.
• The model provides improved predictions of stress–strain behavior over existing models.

Accurate prediction of stress–strain relationship of concrete is of vital importance to accurately predict the overall structural behavior of reinforced concrete members. The various types of concrete that are available in the construction industry today makes it essential that the models developed for the prediction of their behavior are of high versatility. Review of the existing literature revealed that existing stress–strain models for unconfined and confined concretes are limited in their application domains, defined by the parametric range of the experimental results considered in their development. The review also indicated that a unified model that is applicable to normal- and light-weight concretes is not yet available. The aim of the present study was to develop a unified confinement model that is applicable to various types of concrete, ranging from light-weight to high-strength. To this end, two large databases of experimental results of concrete specimens tested under uniaxial and triaxial compression were assembled through an extensive review of the literature. The databases covered a wide range of concrete properties, thereby allowing detailed observation of the important factors influencing the compressive behavior of concrete. The analysis of the unconfined concrete database resulted in the development of expressions for the prediction of elastic modulus, compressive strength and corresponding axial strain of various types of concrete. In addition, through a comprehensive analysis of the combined test database a unified stress–strain model was developed to predict the peak and residual conditions and the complete stress–strain behavior of unconfined and actively confined concretes.