On the refined buffeting analysis of long-span bridges: Which is the proper aerodynamic admittance?

The aerodynamic admittance function (AAF) is one of the most important aerodynamic parameters in evaluating the buffeting responses of long-span bridges. For the bridges with a large span length, the buffeting responses become significant. There is an increasing need to use the proper AAF model to estimate the buffeting responses of bridge girders accurately. This paper aims to study the proper aerodynamic admittance on the refined buffeting analysis of long-span bridges. First, the existing three kinds of AAF models, including two-dimensional (2D) AAF, generalized AAF, and two-wavenumber AAF have been clarified. Next, the turbulence scale effect on the buffeting response of bridges is analyzed by the two-wavenumber buffeting analysis method. The discrepancies between the buffeting displacements calculated by the 2D AAF and the two-wavenumber AAF are compared in various conditions. Then, a statistical approach to identifying the 2D AAF is introduced. The approach can be conducted easily in passive-generated turbulent flow and can identify the 2D AAFs in the entire frequency domain in one measurement. This study demonstrates that the 2D AAF and the strip assumption can be used for the refined buffeting analysis of long-span bridges with large aspect ratios. It is crucial to identify the 2D AAF of bridge girders and use reasonable 2D AAF models to predict the buffeting responses of long-span bridges.