Bridge Deck Aeroelastic Admittance Revisited

The subject matter of the present paper falls within the context of the analysis of the response to wind of long-span bridges. Although the paper stands alone, it should properly be seen as focusing on a single important aspect of such an analysis. For the last few decades, the theory of the response of flexible bridges to wind has grown in sophistication. The problems of buffeting and flutter have been brought together into a unified analytic form. This accomplishment centers on the fact that not only are the static forces and moment on a section of the deck girder experimentally measured on geometrically accurate wind tunnel sectional models, but motional coefficients—flutter derivatives—have also been so obtained for the last quarter-century or more. These experimental values have, for the most part, assured reasonable accuracy in the analytic assessment of flutter and buffeting. In the buffeting case, however, the static coefficients rather than dynamic ones were commonly employed in the force description. This practice usually resulted in erroneous estimates of buffeting response that required correction by invoking empirical frequency-dependent correction factors called aerodynamic admittances. The present paper shows how important central characteristics of such admittances can be seen to be inherent in the measured flutter derivatives.