Synopsis
The occurrence of instabilities associated with general spalling of plain concrete panels is investigated numerically for a thermal history that is similar to that obtained in a standard fire test. The results illustrate the effects of restraint and loading upon the incidence of general spalling. The behaviour of a heated panel is very much influenced by the extent of cracking, due to tensile stress, and by the steepness of the descending branch of the stress-strain curve in compression. The first of these effects may have important implications concerning the use of large quantities of reinforcing steel in heated panels. The second effect is more difficult to assess but it seems possihle that strain softening may be made more serious by the presence of a modest pore pressure in the concrete. The production of steam in the concrete at high temperatures could increase the possibility of the occurrence of general spalling in this way.
