Geometric and Material Nonlinearities in Steel Plates

A numerical model for the analysis of the geometric and material nonlinearities of plate and thin shell steel structures, based on the finite element method, is presented together with its application to some practical examples. To account for the nonlinear behavior of steel, a generalized biaxial constitutive model, based on a kinematic yielding surface, is adopted. The geometric nonlinear effects are included by considering equilibrium on the deformed structure. Among the possible applications, a special concern is the simulation of the existing response beyond the conventional critical design or limiting loads in order to evaluate the actual ultimate capacity of those structures once the secondary resisting mechanisms and strength reserves of the materials are considered. The performance and reliability of the model are shown through the discussion of some numerical examples for which reference theoretical and experimental results are available.