NONLINEAR FINITE-ELEMENT ANALYSIS OF 3-DIMENSIONAL FRAMES

This paper presents a numerical model for the nonlinear analysis of th ree-dimensional frames using the finite element method. The model is b ased on a general variational formulation for thin-walled beams with o pen or closed sections; the mathematical development uses an updated L agrangian description for shallow arches, taking into account geometri cal and material nonlinearities, residual stresses, member initial imp erfections, warping, and connection flexibility. The model has been us ed to evaluate second-order effects and the influence of residual stre sses and joint flexibility on the behavior of plane frames. A semirigi d space frame has been analyzed and the gain in rigidity offered by a horizontal rigid diaphragm has been evaluated.