Numerical modelling of thin-walled stainless steel structural elements in case of fire

In this paper, numerical tests made in stainless steel thin-walled elements, using the
program SAFIR, will be presented.
In order to make these simulations, two main changes in SAFIR were made: i) the
program was changed in order to deal with the stainless steel 2D material properties to be used
with shell elements and ii) the possibility of the program to take into account residual stresses
in shell elements was introduced.
The stainless steel stress-strain relationship at high temperatures, was based on the one
presented in part 1.2 of Eurocode 3 [1], which has no initial linear branch as the case of carbon
steel.
The hardening rule to be used on the shell element formulation could not be exactly
established without an approximation of the Eurocode 3 constitutive law [1].
Due to the fact that the SAFIR procedure to take into account the residual stresses
consists in transforming them first into residual strains and adding them after to the other
initial strains [2], it was necessary to implement a procedure that took in consideration the nonlinearity
of the material stress-strain relationship.
The paper shows the influence of the residual stresses on the ultimate load bearing
resistance of thin-walled stainless steel structural elements in case of fire.