Control of cable vibrations using secondary cable with special reference to nonlinearity and interaction

Experimental as well as analytical studies have been carried out on the controlling effects of a secondary cable in a cable system and efforts have been made to explain the results, especially on the basis of nonlinearity in response and interaction. A cable model consisting of two identical sagged cables in parallel connected by another lighter secondary cable was selected for investigations. Experimental results reveal that nonlinearity in the secondary cable motion induces the main cables to vibrate with nonlinear motion consisting of sub-harmonic components in response in addition to a simple harmonic component. Analytical investigations based on the solution of nonlinear equations of motion, derived from a modal synthesis approach with substructural formulations, show an early jump in the frequency response curve of the main cable. Generation of closely spaced modes due to the addition of the secondary cable plays an important role on its controlling effects on the main cable response through this type of nonlinear interaction.