Aeroelastic Control of Long-Span Suspension Bridges

Abstract

The modeling, control, and dynamic stabilization of long-span suspension bridges are considered. By employing leading- and trailing-edge flaps in combination, we show that the critical wind speeds for flutter and torsional divergence can be increased significantly. The relatively less well known aerodynamic properties of leading-edge flaps will be studied in detail prior to their utilization in aeroelastic stability and control system design studies. The optimal approximation of the classical Theodorsen circulation function will be studied as part of the bridge section model building exercise. While a wide variety of control systems is possible, we focus on compensation schemes that can be implemented using passive mechanical components such as springs, dampers, gearboxes, and levers. A single-loop control system that controls the leading- and trailing-edge flaps by sensing the main deck pitch angle is investigated. The key finding is that the critical wind speeds for flutter and torsional divergence of the sectional model of the bridge can be greatly increased, with good robustness characteristics, through passive feedback control. Static winglets are shown to be relatively ineffective.