Bridge buffeting by skew winds: A revised theory

Abstract

An improved bridge buffeting theory is established with an emphasis on skew wind directions, for both turbulence- and motion-dependent forces. It provides simplifications and generalizations of previously established methods. The formulation starts with a preferred 3D approach, which is suitable when aerodynamic coefficients for different yaw and inclination angles are readily available. The 3D approach includes a new convenient choice of coordinate systems and an intuitive derivation of transformation matrices, supporting clear and compact wind load expressions as well as a more accurate formulation of the quasi-steady motion-dependent forces. When the aerodynamic coefficients have only been obtained for wind normal to the bridge girder, an alternative 2D approach is provided. The 2D approach, where only the normal projection of the wind is considered, is further expanded to include mean wind directions that are both yawed and inclined, axial forces in the longitudinal direction (1D) in an optional 2D ​+ ​1D format, and forces due to all in-plane and out-of-plane motions. All expressions are first presented in a compact non-linear format and then linearized through numerous multivariate Taylor series approximations. A general, more straightforward and more accurate framework is thus established for both time- and frequency-domain analyses of the buffeting response.