Experimental investigation on vortex-induced vibration of a long-span rail-cum-road bridge with twin separated parallel decks

Long-span rail-cum-road bridges with twin separated parallel decks have become a recommended structural form because of their superior traffic capacity. However, because of inconsistent dynamic characteristics of highway and railway bridges, different wake characteristics and special aerodynamic interference between the asymmetric twin decks, the vortex-induced vibration (VIV) characteristics for twin-deck bridges are more complicated. In this paper, wind tunnel tests were carried out to study the VIV characteristics of a long-span rail-cum-road bridge with twin separated parallel decks. Furthermore, fluctuating wind pressure of the highway and railway girders was measured to discuss the vibration phenomenon. The results indicated that the VIV of the railway girder only occurs upstream, while the VIV of the highway girder occurs both upstream and downstream. The aerodynamic interference has an impact on the VIV response of both upstream and downstream girders. 3° is still the most unfavorable wind incidence angle for the twin parallel deck bridges. Increasing structural damping helps to suppress VIV, but it cannot completely suppress the occurrence of VIV. Adjusting the wind fairing angle of the highway girder and sealing the handrail at intervals are both effective in controlling VIV, but the effects are different for upstream and down girders. For the twin separated parallel decks bridges, the VIV suppression effect of the aerodynamic measures needs to be comprehensively considered from the overall consideration of the twin decks under different incoming flow directions. •Vortex-induced vibration (VIV) and VIV-suppress measures for a rail-cum-road bridge are investigated in wind tunnel tests.•Necessity of considering the aerodynamic interference and direction of incoming flow of rail-cum-road bridges is highlighted.•The VIV suppression effect needs to comprehensively considered both twin girders under different incoming flow directions.