Vortex‐Induced Vibrations of Flexible Bridges

One of the recurring aerodynamic concerns of both existing and projected new and flexible bridges, typically those of long span, is the possibility that the deck may be set into periodic oscillation by cross winds of relatively low velocity. This general phenomenon, regardless of the specific details of the local flow about the structures, has been termed “vortex‐induced oscillation.” In this paper, prediction of the expected vortex‐induced response of flexible bridges is treated as a two‐step process. In the first step, the parameters of a mathematical model, used to describe the response of a rigid, elastically mounted, scaled section model of a bridge are identified. A technique for estimating these parameters using wind‐tunnel test results is proposed. In the second step, model parameters are used in the equation of motion of the prototype bridge to obtain its response. A method that accounts for the effect of imperfect spanwise correlation of aerodynamic forces on flexible‐bridge response, based on measurements on rigid section models, is developed. Design applications are discussed and an example is provided.