To mitigate vortex-induced vibrations in long-span bridges, which approach is commonly implemented?

• A. Increasing deck thickness only.
• B. Employing tuned mass dampers or dampers and aerodynamic shaping.
• C. Removing all dampers to increase natural frequency.
• D. Painting the surface to reduce vortex shedding.

Answer: (B)

Vortex-induced vibrations arise from alternating vortices shed by the deck, creating periodic forces that can excite a bridge’s natural modes. The most effective mitigation combines energy dissipation with flow modification: tuned mass dampers or other dampers absorb energy as the structure vibrates, lowering the amplitude, while aerodynamic shaping alters the deck geometry or adds flow-control features to disrupt coherent vortex shedding and weaken the fluctuating lift. Together, these approaches directly address both the excitation and the energy in the system, providing robust damping across wind conditions.

Increasing deck thickness doesn’t reliably reduce VIV; it can shift stiffness/mass in ways that don’t guarantee less vibration. Removing dampers removes a key energy sink, worsening vibration. Painting the surface to reduce vortex shedding is not a practical or effective method for VIV control, since paint color or surface coating offers negligible impact on the vortex shedding dynamics compared with dedicated damping and aerodynamics.