Numerical investigation of damage and spalling in concrete exposed to fire

There exists continued controversy over the underlying causes of thermally induced spalling in concrete, with thermally induced stress and internal pore pressures being variously cited as the critical factors. The results of a series of numerical experiments designed to investigate these phenomena are presented here. The experiments were carried out using a fully coupled hygro-thermal-mechanical finite element model, with the development of mechanical damage considered indicative of certain spalling behaviours. The results indicate that thermally induced stresses are the dominant factor in the cases considered with pore pressures playing, at most, a secondary role. Initial investigations concerning the damage model indicate that the choice of equivalent strain measure is critical in producing observed spalling behaviours, but that other factors, while influencing the development of damage do not affect the major finding of this work.