A thermo-plastic damage model for cyclic loading of concrete at elevated temperatures

In this paper a new thermo-plastic damage model for plain concrete subjected to combined thermal and cyclic loading is developed using the concept of plastic-work-hardening and stiffness degradation in continuum damage mechanics. Two damage variables are used, one for mechanical action and the other for thermal action. The concrete model is based on the non-associated flow theory of plasticity with a scalar hardening parameter, a multi-criteria yield function. Further, thermo-mechanical interaction strains have been introduced to describe the influence of mechanical loading on the physical process of thermal expansion of concrete. The constitutive relations for elastoplastic responses are decoupled from the degradation damage responses by using the effective stress concept. This method provides advantages in the numerical implementation. Efficient computational algorithms for proposed thermo-plastic damage model are subsequently explored and performance of this model is demonstrated with numerical examples.