THE UNLOADING OF BUILDING-MATERIALS SUBMITTED TO FIRE

The unloading of building materials is considered in uniaxially oriented structures. It is shown how the uncertainty encountered in numerical simulations between loading or unloading can be resolved when using the principle of Duhamel and assuming that the plastic strain is not affected by a temperature variation. A solution is also proposed to consider the inelastic behaviour of a material with a non-linear stress-strain relationship like the linear-elliptic one that is often used for steel. The analysis of three composite steel-concrete elements tends to prove that the consideration of inelastic behaviour is not critical in simply supported beams. It seems to be of more importance in an hyperstatic beam and even more in a centrically loaded composite column. © 1990.