Theory and Full-Bridge Modeling of Wind Response of Cable-Supported Bridges

Abstract

As is well known, long, suspended bridge spans require, in the design stage, careful study of their resistance and response to site winds. This has driven, on the one hand, detailed quantitative observation of bridge models in the wind tunnel and, on the other, a steady development and refinement of parallel theory. Currently, both aspects have arrived at good stages of sophistication, although with continued room for improvement. Successes in the extension of bridge spans to record-breaking lengths are mainly due to progress in wind-resistant design, a primary component in the design of long-span bridges. Recently, multimode flutter and buffeting analysis procedures have been developed. These procedures, which were based centrally on frequency-domain methods, take into account the fully coupled aeroelastic and aerodynamic response of long-span bridges to wind excitation. This paper briefly reviews the current state of the art in long-span bridge wind analysis, emphasizing the analytical infrastructure. The focus then turns to exhibit an example of application of the theory to the stability (flutter) and serviceability (buffeting) analyses of a new long-span bridge in North America. This example not only demonstrates the application of the theory to a real structure but also serves to highlight some insights into the versatility that is gained by this analytically based approach. The results demonstrate that the analytical method with appropriate inputs and a complementary full-bridge model agree even for relatively unusual incoming turbulence in the flow caused by the presence of structures upstream of the bridge. This paper seeks to exhibit recent developments in the field to the interested structural/bridge engineer, outline alternative procedures available for assessment of wind effects on cable-supported bridges, and provide an overview of the basic steps in the process of a typical aerodynamic analysis and design.