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Wind and Structures
  Volume 25, Number 4, October 2017, pages 397-413
DOI: https://dx.doi.org/10.12989/was.2017.25.4.397
 


Ground effects on wind-induced responses of a closed box girder
Wenhao Mao and Zhiyong Zhou

 
Abstract
    When bridges are constructed with lower heights from the ground, the formed channel between the deck and the ground will inevitably hinder or accelerate the air flow. This in turn will have an impact on the aerodynamic forces on the deck, which may result in unexpected wind-induced responses of bridges. This phenomenon can be referred to \"ground effects.\" So far, no systematic studies into ground effects on the wind-induced responses of closed box girders have been performed. In this paper, wind tunnel tests have been adopted to study the ground effects on the aerodynamic force coefficients and the wind-induced responses of a closed box girder. In correlation with the heights from the ground in two ground roughness, the aerodynamic force coefficients, the Strouhal number (St), the vortex-induced vibration (VIV) lock-in phenomena over a range of wind velocities, the VIV maximum amplitudes, the system torsional damping ratio, the flutter derivatives, the critical flutter wind speeds and their variation laws correlated with the heights from the ground of a closed box girder have been presented through wind tunnel tests. The outcomes show that the ground effects make the vortex-induced phenomena occur in advance and adversely affect the flutter stability.
 
Key Words
    ground effects; wind tunnel test; closed box girder; aerodynamic force coefficients; St number; VIV; critical flutter wind speeds
 
Address
Wenhao Mao: State Key Laboratory for Disaster Reduction in Civil Engineering, 1239 Siping Road, Shanghai, China;
Key Laboratory of Ministry of Communications for Bridge Structure Wind resistance, 1239 Siping Road, Shanghai, China
Zhiyong Zhou: State Key Laboratory for Disaster Reduction in Civil Engineering, 1239 Siping Road, Shanghai, China
 

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