Real-Time Aerodynamics Hybrid Simulation: A Novel Wind-Tunnel Model for Flexible Bridges

Despite rapid development in computational fluid dynamics, semiempirical analyses based on parameters identified from spring-mounted sectional models are still widely used to examine wind-induced effects on bridges. In addition, wind tunnel results from full-bridge aeroelastic models, viewed as the most comprehensive representations, are typically a final check for wind design of long-span cable-supported bridges. There are several well-known limitations associated with conventional wind tunnel testing of both sectional and full-bridge models. For example, structural nonlinearities and large deformations are difficult to simulate in sectional models, and only a limited number of modes can be accurately simulated in full-bridge aeroelastic models. To advance aeroelastic modeling of flexible bridges in the wind tunnel, a slightly different version of the real-time hybrid simulation (RTHS) techniques, frequently used in various branches of engineering, is developed here. Specifically, the skeleton of the sectional or full-bridge model, characterizing the dynamic properties (e.g., mass, damping, and stiffness of the structure), is numerically simulated using computational structural dynamics, while its skin, characterizing the aerodynamic and aeroelastic properties, is physically modeled in the wind tunnel. Aerodynamic inputs (gusts) are applied directly on the skin in the wind tunnel, while aeroelastic inputs (motions) are represented by the simulation outputs of the bridge skeleton. On the other hand, the dynamic inputs to the bridge skeleton are acquired from the measured forces (and moments) on the bridge skin. The interactions between the skeleton and skin of the bridge are accomplished through a system consisting of sensors, a network of electromagnetic actuators, and controllers. The time history of the wind-induced bridge responses can be obtained at the end of the proposed real-time aerodynamics hybrid simulation (RTAHS). The feasibility of the RTAHS methodology is demonstrated by a numerical example involving both linear and nonlinear wind-induced forces on the bridge deck.