Viaducts have been constructed in a large city to solve traffic congestion in the city. In recent year, the long viaducts are constructed from the viewpoint of the construction cost reduction. In some cases, a parallel viaduct is adopted. Since most viaducts in the city have the sound-barrier wall, they are susceptible to vibration under the wind action. The present paper deals the aeroelastic. instability of the parallel long viaduct with sound-bather wall and the suppression of the vibration by T M D. In the experiments, the leeward viaduct of the parallel viaduct vibrated under wind action by the influence of the wake of the windward viaduct. The divergence force worked on the leeward viaduct was very strong. It was considered that it was difficult to adopt the aerodynamic countermeasure on the leeward viaduct for suppressing the aeroelastic vibration. The another method was T M D. In this paper, it is introduced that the T M D is effective for the control of the aeroelastic vibrations of the leeward viaduct under wind action.
