Numerical Modelling Of A Single Storey Industrial Building At Elevated Temperature - Comparison Between The 2d And 3d Analyses.

Abstract

Single storey industrial buildings with steel structure composed by portal frames
disposed in parallel constitute a very frequent kind of construction. The computational
simulation of steel structures under fire conditions is usually performed by the twodimensional
finite element analysis of the structure. In this way the analysis of the behaviour
of single storey industrial buildings is performed either by the simulation in the plane of the
steel portal frame or, simply the roof truss.
However, the two-dimensional analysis takes into account neither the out-of-plane
instabilities, nor the out-of-plane redistribution of efforts. These effects can play an important
role in the structural performance of a building in a real fire situation.
In this paper a comparative study of two- and three-dimensional models of a portal frame
industrial building under elevated temperatures is presented. The importance of the out-ofplane
effects and the adequacy of the plane model to represent the real behaviour is
discussed.
The computer program SAFIR5 , developed at University of Liege for analysis of structures
submitted to fire, was used in all the simulations. Amongst other features, the structural
analysis performed by SAFIR considers: the effects of large displacements; the non-linear
variation of material properties with the temperature; the effect of the thermal elongations;
the evolution of the structural behaviour given as a function of time (an automatic time step
can be used).