Study on the Mechanism of Bird-Cage Buckling of Armor Wires Based on Experiment

Armor wires which are typical spiral wound structures are widely applied to flexible structures in ocean engineering, such as flexible pipes and umbilical cables. Birdcage buckling phenomenon would appear under the condition of damage of the cover sheath and strength tapes when armor wires are subjected to high axial compression which exceeding its critical load. In this paper a special experiment device is designed to simulate the armor wires winding a cylinder. Based on the experiment, the birdcage buckling mechanism of spiral wound steel wire is analyzed. The global configuration time-history of spirally wound steel wire is recorded to find the critical buckling load with the increasing compression displacement. At the same time, strain state at the critical position is analyzed, which could provide a reference for curved beam’s buckling research. Moreover, sensitivity analysis of critical buckling load is investigated with consideration of some influencing factors such as spiral wound radius, length and pitch. Finally, the relationships between them and critical buckling compression load are quantified. The experimental results could guide the anti-buckling design of armor wires for flexible pipe or umbilical cables.