Elastic and inelastic responses of columns after sudden loss of bracing

Abstract

A pinned column with initial deflection and an internal brace is investigated. The brace is modeled as a translational spring. Axial compressive loads are applied at the brace and the top of the column, and the equilibrium shape of the column is determined. The critical loads for the perfect column are computed analytically for several load combinations.

The dynamic response of the column after sudden loss of bracing is analyzed using Galerkin’s method. With the consideration of the effects of the bracing location and the bracing stiffness, the maximum deflection of the column during motion is determined. The contribution of damping effects to the maximum deflection of the column is examined. Damping effects in the Galerkin method are compared to results from the finite element method (based on ABAQUS).

The plastic dynamic analysis is carried out using ABAQUS. Both residual stresses and damping effects are considered, and the spread of plasticity during the motion is investigated. The cases studied include equal and unequal spans, and axial loads below and above the load which causes the column to collapse.