engleski

Nonlinear stability analysis of thin-walled frames using UL-ESA formulation

This work presents a one-dimensional finite element formulation for non-linear analysis of spaced framed structures with thin-walled cross-sections. Applying the updated Lagrangian incremental formulation and non-linear displacement field of thin-walled cross- section, which accounts for restrained warping and includes second-order displacement terms due to large rotation effects, equilibrium equations of a straight beam element are firstly developed. Due to the non- linear displacement field, the geometric potential of semitangential moment is obtained for torsion and bending moments, respectively. In such a way, the joint moment equilibrium conditions of adjacent non- collinear elements are provided. Force recovering is performed according to the external stiffness approach. Material non-linearity is introduced for an elastic-perfectly plastic material through the plastic hinge formation at finite element ends and for this a corresponding plastic reduction matrix is determined. The interaction of element forces at a hinge and the possibility of elastic unloading are taken into account. The effectiveness of the numerical algorithm discussed is validated through the test problem.

thin-walled frame ; non-linear stability ; beam element ; non-linear displacement field ; external stiffness approach ; plastic hinges

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