Intermittent response of tall structures subjected to turbulent vortex-induced vibrations

A new model for calculating the response of a structure subjected to turbulent vortex-induced vibration is proposed. The model takes into consideration the nonlinear coupling between the structure and its wake. The concept of parametric excitation is then used to decouple the structure-wake differential equations leading to a single degree of freedom equation describing the response of the structure. The turbulent vortex-shedding forces are then simulated from a narrow-banded spectral density that is carefully chosen to represent the periodic vortices shed in the wake of the structure and the turbulence generated by the flow. The Fast Fourier Transform is used to generate force samples from the selected spectral density curve. The response of the structure due to the generated wind forces is obtained by numerically integrating the model. The numerical results are then verified analytically using stochastic averaging. The results show that the response is neither periodic nor purely random. It is rather intermittent, damping out after reaching high peaks. The suggested innovative response trend is expected to have a great impact on the damping techniques used in controlling building vibrations.