Numerical Modelling of Thermal Weakening Effect on Compressive Strength of Concrete

Concrete strength reduces considerably at elevated temperatures. In the present study, this weakening effect is numerically modelled with the embedded discontinuity finite elements approach. Concrete material is modelled
mesoscopically as an aggregate-mortar bi-phasic structure made of Portland cement and granite. Initial crack populations are applied to the cement matrix to add randomness. The concrete material is linear elastic until violation of the Rankine criterion upon which a crack, with a normal parallel to the first principal direction, is introduced into a constant strain triangle element. This fracture model appears to replicate the salient features of concrete fracture in compression. The thermally induced cracking is simulated by solving the underlying thermo-mechanical problem with an explicit staggered
scheme using mass scaling to increase the critical time step. Numerical 2D simulations of concrete under uniaxial compression demonstrate that the present method predicts the thermal weakening effect with an engineering accuracy.