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Summary The structural-aerodynamic modelling and dynamic stabilization of a three-dimensional suspension bridge model is considered. Our emphasis is on investigating the effectiveness of leading and trailing edge flaps in suppressing aeroelastic instabilities. The East Great Belt Bridge is chosen as a design example, and its aeroelastic limits are computed using both thin aerofoil theory and flutter derivatives. The problem is cast in an efficient reduced size finite element formulation with aerodynamic forces expressed in the Laplace domain by use of a high-fidelity rational function approximation. Circulatory aerodynamic forces are modelled using a feedback loop for every element, and the problem is expressed in a form suitable for implementation of modern control techniques. The structure's full multimodal response is considered, and numerical predictions show very good agreement against experimental data from the literature. In order to account for modelling errors and uncertainties while designing the controller, elements from robust control theory are invoked. The stability and robustness of the bridge when fitted with flaps controlled by optimal and suboptimal H∞ controllers are discussed for varying lengths of control surfaces along the suspended span as the optimum configuration for aerodynamic performance is investigated. Copyright © 2016 John Wiley & Sons, Ltd.

This study presents a system based on passively controlled leading- and trailing-edge flaps that is designed to suppress wind-induced instabilities such as flutter and torsional divergence. The utility of the approach is demonstrated on a three-dimensional bridge model. Particular emphasis is placed on the early stages of the deck erection process when the bridge is particularly vulnerable to flutter. The flaps are activated by the deck's movements though passive phase-compensating mechanisms comprising of springs, dampers and inerters. It is demonstrated that optimised compensator parameters, and optimum hinge locations, result in a substantially improved deck aerodynamic performance. Particular importance is given to ensuring that the controlled system has good closed-loop ‘robustness’ properties, or in other words, that the controlled system has a high tolerance to parameter variations and uncertainties in the system dynamics. The practical use of a nonlinear optimisation algorithm with a FE bridge aeroelastic model, which includes the flap dynamics, necessitates the use of reduced-order models. A novel model reduction procedure that is based on the retention of dominant poles is introduced into the aeroelastic modelling framework. Multimodal interactions are observed at the various erection stages and conclusions are drawn with regard to the contributions of various modes of vibration to aeroelastic instabilities. The main advantage of this approach lies on the passive system's simplicity and its ability to simultaneously increase the flutter and torsional divergence boundaries. The Humber Bridge in the U.K. is chosen as a study example for numerical simulations.

This study investigates different ways to passively suppress wind-induced instabilities such as flutter and torsional divergence. The control system design study is based on a sectional flexible bridge model interacting with a constant velocity airstream. Two different strategies are considered, separately and in combination. The first makes use of trailing and leading flaps adjacent to the bridge deck, the motion of which is triggered by the deck’s movement through a combination of springs, dampers and inerters at the hinged connection. Emphasis is placed on the effect of the flap hinge location and an optimization procedure is used for determining the compensator parameters that result in favorable aeroelastic properties. The second approach reexamines the efficacy and limitations of using Tuned Mass Dampers (TMDs) placed inside the bridge deck for controlling self-excited motion. We conclude by combining the two approaches and introducing a kinematic constraint between the masses of the TMD and the flaps. This combined mechanical system, referred to as the Flap Mass Damper (FMD), combines favorable aerodynamic properties of the flaps with a driving force provided by the vibrating mass. Consequently it has the advantage of not requiring complex and often impractical linkages in order to transmit the deck motion to the flaps. Special attention is given to ensuring that the passive control system attains optimum robustness properties and maximizes tolerance to uncertainties. Uncertainties are quantified in a series of simulations showing how the alteration of the bridge’s natural frequencies affect the stability of the controlled system. The Humber Bridge in the U.K. is chosen as an example for the numerical simulations.

The 3D structural and aerodynamic modelling of a long span suspension bridge is considered and emphasis is placed on the simulation of the aeroelastic properties during the deck erection process. We then employ a leading-and trailing edge flap configuration on a finite deck length around the mid-point of the main span and investigate ist effectiveness in raising the critical flutter and divergence speed. In order to account for modelling errors and uncertainties in the controller design process we invoke elements from robust control theory and a nonlinear optimization algorithm is proposed to achieve the performance objectives.