Vortex induced vibration analysis of a twin-box bridge deck by means of 3D LES simulations

Twin-box decks are prone to suffer vortex-induced vibrations (VIV). Although this phenomenon has been widely studied experimentally, there are still gaps in our understanding about the complex interplay between the incoming flow, the windward and leeward boxes, and the potential oscillation of the deck. This work exploits the ability of 3D LES simulations to simulate complex aeroelastic phenomena to delve into the linkage between aerodynamic forcing and heave oscillation through detailed analysis of comprehensive datasets. Several reduced velocities are studied in the VIV-prone range of the bare deck of the Stonecutters Bridge, analysing the spectra of the time-histories of force coefficients, for the overall deck and individual boxes, and heave oscillations. Similarly, the contribution of the local lift coefficient has been studied along with the work done by the deck and the individual boxes at different reduced velocities. It has been found that the leeward box is the one governing the overall VIV response of the deck. The spanwise-averaged time-averaged work distribution around the deck permits the identification of those regions contributing to the heave oscillation build-up, enabling the design of aerodynamic countermeasures for mitigation of VIV tailored for the specific deck geometry and dynamical properties of the deck.