EAPSI: Improving the Safety and Durability of Cable-supported Bridges in Wind

Gibbs Maria M, South Bend IN

Investigators

Abstract

Long span cable-supported footbridges are particularly vulnerable to wind-induced failure due to their light and flexible nature. This project seeks to identify key characteristics of a standardized suspension footbridge in order to predict how the structure will respond during a wind event. This research will be conducted in collaboration with Dr. Ge Yaojun, a noted wind engineering expert. State of the art wind tunnel facilities at Tongji University in Shanghai will afford the unique opportunity to perform full-scale deck section wind tunnel experiments which will be used to assess safety of this type of bridge in the event of a wind storm and provide guidelines for span limits and wind mitigation strategies. The dynamic characteristics of these footbridges are widely unknown and no previous experimental investigation of the structures under wind loading has been performed. Discovering their fundamental characteristics will lay the groundwork for the structures to serve as a test bed for the investigation of non-linear features in the behavior of flexible bridge structures. Developing a predictive wind analysis framework and ultimately a design standard which incorporates wind vulnerability for flexible footbridges hinges on the identification of bridge deck aerodynamic characteristics. The framework will incorporate a numerical model built in ANSYS which uses flutter and buffeting forces reliant on section model wind tunnel tests. Bridge deck motion will be modeled with two degrees of freedom in the vertical and rotational directions. These wind-induced loads will be modeled using both traditional and updated schemes. These schemes require aerodynamic coefficients and aerodynamic and aeroelastic transfer functions measured using section model tests in the wind tunnel Access to full scale monitoring data from a number of existing footbridges which incorporate this standard deck detail will allow for an unprecedented look at how one can model these types of bridges in a hybrid wind tunnel/computational approach and also the prospect of capturing any scaling error that may distort response predictions compared to the observed behavior of the actual structure under wind loads. This NSF EAPSI award support the research of a U.S. graduate student and is funded in collaboration with the Chinese Ministry of Science and Technology.