Effects of Turbulence on Bridge Flutter Derivatives

Bridge flutter derivatives have heretofore been obtained from models almost exclusively tested under oncoming laminar flow conditions. This paper demonstrates how a section model teest may be set up and the results interpreted to obtain bridge deck flutter derivatives under conditions of oncoming turbulent flow. New theory is necessary in the turbulent flow case, and this is developed in the paper. The technique described amounts to a system identification method in which aerodynamic results are inferred from a theoretical model plus measured results of turbulent wind components, together with the motion they cause in the model. Flutter derivative results for an arbitrary model shape, obtained under a particularly pronounced form of turbulence that does not necessarily duplicate the natural turbulent wind over a prototype, are compared with analogous results obtained under laminar flow.