Nonlinear thin shell finite element for steel and concrete structures subjected to fire: Theoretical development

This article describes the features of a quadrilateral thin shell element, based on Marguerre's theory that has been implemented in the finite element program SAFIR (from the University of Liege.) The element has four nodes (one at each corner) and each node has six degrees of freedom, i.e., three translations and three rotations (the sixth degree of freedom is a true one, which can be assimilated to the in-plane rotation.) This article presents some theoretical developments regarding the element formulation. The algorithm strategies for isotropic material (steel for example) and non-isotropic material (concrete) and their modifications for elevated temperatures are described. Two verifications examples are presented (the patch test and Lee's frame at elevated temperatures). © 2004, Baywood Publishing Co., Inc.