Three-Dimensional Modeling of Inelastic Buckling in Frame Structures

Keywords: Three dimensional (3D) models.  Inelastic buckling.  Displacement.  Constitutive models.  Rotation.  Zipper frames.  State space approach.  Geometric nonlinearities.  Material nonlinearities.  Corotational approach.  Models.  Frame structures.

Abstract: This report offers a novel formulation capable of solving problems with displacement and material nonlinearities in a unified way. Thus, the State Space approach is selected because all the basic equations of structures: equilibrium, compatibility and plasticity are solved simultaneously and thus the global and local states are mutually and explicitly dependent. To incorporate geometric nonlinearities, the Corotational approach is adopted. And to incorporate material nonlinearities, the formulation developed by Simeonov and Sivaselvan is included. A model of the first story of the zipper frame was analyzed with the new formulation and its results compared to experimental data. The results presented show that the new formulation can reproduce the features of the test and it is very sensitive to all the model parameters.