Semiactive Fuzzy Logic Control of Suspension Bridge Flutter

Abstract

A semiactive tuned mass damper (STMD) system with variable damping is used to control the flutter instability of long-span suspension bridges. For this purpose, a combined vertical and torsional model of a TMD system, which is placed at the middle of the center span, is used. This system has two degrees of freedom, which are tuned close to the frequencies corresponding to vertical and torsional symmetric modes of the bridge, that get coupled during flutter. The variable damping of the system is chosen through a fuzzy logic controller using the displacement and velocity at the center of the bridge as the inputs. The transient response of the bridge due to a given initial condition in presence of the wind self-excited forces is controlled so that critical flutter wind speed for the bridge is enhanced. The methodology is applied to increase the flutter wind speed of the Thomas Suspension Bridge. Also, a numerical study is conducted to investigate the effectiveness of the semiactive control scheme.