Towards a risk analysis of bridge decks prone to lock-in oscillations

The risk in terms of average number of days per year a bridge must be closed to traffic due to vortex-induced vibrations represents a useful index to compare different bridge deck solutions. This estimation requires the probabilistic treatment of both wind and wind-structure interaction. This work attempts to accomplish such a difficult task by developing the first steps towards a complete risk analysis procedure. The performance-based design approach, a PEER-type equation, wind tunnel tests, wind and vortex-induced vibration models are the main ingredients. The procedure is applied to an idealized case study and through a sensitivity analysis the effects of several assumptions are shown. The influence on the bridge deck response of the structural damping ratio, the uncertainty on the aeroelastic parameters and the spanwise correlation of the aeroelastic forces is highlighted. In particular, the bridge deck response results only slightly modified by a reasonable variation of the aeroelastic parameters of the model. Moreover, the risk value is significantly influenced by the lock-in response shape as well as the extension of the range of synchronization.