Probing the stability landscape of prestressed stayed columns susceptible to mode interaction

Prestressed stayed columns are structural systems where the compressive load-carrying capacity is enhanced through pre-tensioned external cable stays. Recent theoretical studies using analytical and nonlinear finite element models have shown that, under certain configurations, this enhancement leads to a sequence of closely spaced bifurcation points beyond the critical one. This undesirable characteristic can give rise to dangerously unstable interactive post-buckling behaviour including `mode jumping' and `snaking' phenomena. Even though these highly nonlinear behaviours can be readily modelled using numerical methods, they cannot be verified robustly using traditional quasi-static testing techniques based on force or displacement control at a single point. The current work explores a novel testing concept for potential experimental implementation, from the theoretical and numerical point of view. The concept allows the stability landscape of prestressed stayed columns to be ascertained by controlling the shape of the structure at multiple points. By controlling the mode shape of the structure, it is possible to traverse limit points, path-follow otherwise unstable equilibria, pinpoint bifurcation points and branch-switch between different post-critical segments of the equilibrium manifold. To explore the feasibility of the new testing method, we have created a virtual instantiation of the experiment in the commercial finite element package Abaqus, coupled to a control algorithm that coordinates the movements of the different control points. A number of different stability phenomena that have previously been identified analytically and numerically are reproduced successfully in the virtual test environment. Moreover, a noise sensitivity study is conducted to assess the robustness of the experimental technique proposed herein. The present work lays the foundation for physically assessing the stability landscape of prestressed stayed columns in a more comprehensive way.