Analytical study on flutter suppression by eccentric mass method on FEM model of long-span suspension bridge

A method of suppression of flutter in long-span bridges based on the concept of eccentric mass is presented in this paper. The auxiliary mass is placed on the windward side of a bridge deck to shift the center of gravity, and thus, the aerodynamic moment acting on the deck is reduced, resulting in an increase in the flutter wind speed. The state-space model of aerodynamic forces on the bridge deck section with eccentric mass is derived through a rational function approximation of unsteady aerodynamics. The parameters of the rational function model of a section of the bridge are obtained from the flutter derivatives experimentally determined. Then, the FEM model of full suspension bridge with main span of 2500 m is derived. It is shown from numerical study that addition of an eccentric mass gives a significant improvement in the flutter wind speed. Distributing the eccentric mass in the center-span is found to be the most effective.