Modelling of hygro-thermal behaviour of concrete at high temperature with thermo-mechanical and mechanical material degradation

A mathematical model for analysis of hygro-thermal behaviour of concrete as a multi-phase porous material at high temperatures, accounting for material deterioration, is presented. Full development of the model equations, starting from the macroscopic balances of mass, energy and linear momentum of single constituents is presented. Constitutive relationships for concrete at high temperature, including those concerning material damage, are discussed. The classical isotropic non-local damage theory is modified to take into account the mechanical- and the thermo-chemical concrete damage at high temperature. The final form of the governing equations, their discretised FE form, and their numerical solution are presented. The results of two numerical examples, concerning fire performance of 1-D and 2-D HPC structures, are discussed.