3-D Inelastic Behavior of Tubular Members Supported on Nonlinear Rotational Springs

The paper considers a theoretical analysis of the inelastic response of tubular brace members of offshore jackets which are supported on non-linear rotational end springs and subjected to axial load and generally applied end bending moments. The present analysis is based on the concept of 3-D plastic hinge formation. The method assumes that plasticity is confined to discrete plastic hinges while the rest of the member remains elastic. This allows a rapid non-linear analysis of the axial behaviour of the member by a sequence of elastic solutions of the classical beam-column equations. It is shown that the model is able to simulate closely and efficiently the 3-D inelastic behaviour of brace members under the above support conditions.