On the modeling of thermo-mechanical concrete for the finite element analysis of structures submitted to elevated temperatures

In this paper a 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 one. 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 path on the physical process of thermal expansion of concrete. The constitutive relations for elastoplastic response are decoupled with the degradation damage response by using the effective stress concept. The efficiency of the proposed thermo-plastic damage model is demonstrated through numerical examples with the experimental counterparts.