Equivalent static wind loads for buffeting response of bridges

In current design practice, the dynamic wind loads are described in terms o f the equivalent static wind loads based on the gust response factor. This approach results in a distribution of the equivalent static loading similar to the mean static wind load distribution, which may not always be a physi cally meaningful and realistic load description. In this paper, the equival ent static load representation for multimode buffeting response of bridges is formulated in terms of either a weighted combination of modal inertial l oad components, or the background and resonant load components. The focus o f the present study is on the determination of weighting factors of equival ent static load components in which the correlation among modal response co mponents due to structural and aerodynamic coupling effects is taken into c onsideration. It is noteworthy that the equivalent static load distribution s vary for each response component. The proposed approach particularly help s in extracting design loads from full aeroelastic model test results by ex pressing the dynamic loads in terms of the equivalent static loads. This fa cilitates in drawing useful design input from full aeroelastic tests, which have been employed mostly for monitoring the response of bridge models at selected locations. A simplified formulation is also presented in a closed form when wind loading information is available and coupling in modal respo nse components is negligible, which can be very attractive for the prelimin ary design application. Examples are presented to illustrate modeling of th e equivalent static loading and to demonstrate its effectiveness in bridge design.