Hygro-thermo-mechanical analysis of spalling in concrete walls at high temperatures as a moving boundary problem

A mathematical model allowing coupled hygro-thermo-mechanical analysis of spalling in concrete walls at high temperatures by means of the moving boundary problem is presented. A simplified mechanical approach to account for effects of thermal stresses and pore pressure build-up on spalling is incorporated into the model. The numerical algorithm based on finite element discretization in space and the semi-implicit method for discretization in time is presented. The validity of the developed model is carefully examined by a comparison between experimental tests performed by Kalifa et al. (2000) and Mindeguia (2009) on concrete prismatic specimens under unidirectional heating of temperature of 600 ${\deg}$C and ISO 834 fire curve and the results obtained from the numerical model.