Aeroelastic Galloping of Prismatic Bodies

Galloping oscillations of long prismatic bodies with aerodynamically unstable cross sections in the direction normal to that of the acting steady wind are analyzed. Principally, the steady vibrations are described under different conditions on the basis of the quasi-steady approach which leads to the nonlinear differential equation of self-excited oscillations. The first approximation of the Bogoliubov and Krylov method is used with one degree of freedom systems and energy considerations are applied with continuous systems. It is found that the steady amplitudes are determined by an algebraic equation which is formally identical for all systems both simple and with many degrees of freedom. It is proved that for all structures having a certain type of cross section and the same modes of free vibrations, but arbitrary mass and damping, the steady amplitudes are described by the solely universal response curve. This universal response curve can be either calculated or derived from amplitude measurements on an arbitrary model. Experiments on a cantilevered square prism are described herein.