Generic Model Stress-Strain Relationship for Concrete in Compression at Elevated Temperatures

This paper presents a generic uniaxial constitutive model of the complete stress-strain curve of concrete in compression, adaptable to elevated temperatures solely by temperature-dependent material parameters. The pre-peak regime is divided into an initial linear part until the point of first yielding and a subsequent nonlinear part, starting with a tangent slope equal to the elastic modulus. The post-peak regime is split into two parts by the inflection point of the descending branch and ends at a predefined degree of softening. Additionally, elastic stiffness degradation is considered in the post-peak regime. First, analytical expressions for the different parts are derived and then the model is validated against experimental data of normal-strength concrete and self-consolidating concrete at elevated temperatures, including data from specimens heated under sustained loading. Finally, the model performance is discussed with respect to existing models in the literature and to the available design code models.