Mitigation Strategies of Wind Risk in Suspension Bridges: Some First Numerical Results

Some design strategies for the mitigation of wind risk on suspension bridges are presented and compared by means of numerical simulations and a risk-based analysis. Among all the possible wind-induced issues, the ultimate limit state of bridge collapse due to aeroelastic instability and the serviceability limit state of bridge closure to traffic due to excessive buffeting vibrations are considered. Some examples of design aimed to the vulnerability reduction are offered in the special case of a suspension bridge. In particular the possible advantages of introducing crossed hangers, secondary cables with opposed curvature, or tuned mass control devices are evaluated. The computational approach is based on the finite-element discretization the structure and on semi-empirical crosssectional models for the wind loading. In order to account for the structural nonlinearities of the cables and for the localized damping, time-domain simulations are performed and unsteady selfexcited wind loading is modelled through an indicial function approach. The examples show the versatility of the developed computational approach and the potentiality of the risk analysis. Also, the effectiveness of tuned mass control systems against flutter and excessive buffeting vibrations is highlighted.