Suspension bridges with closely spaced parallel dual main cables may experience significant aerodynamic interference effects, and particularly are prone to significant wind induced vibration due to the low frequency and rapidly varying cross-section shape of the main cable in the construction phases without the constraint of slings.In order to investigate the vibration characteristics of the parallel dual main cables in construction phases, five typical segmental models of dual main cables in the parallel configuration were designed for a very long-span suspension bridge with a main span of 2180 m. Based on the wind tunnel tests, the wind-induced vibrations of the dual main cables on one side in construction phases were studied and then compared to those of the single main cable on one side with the same parameters. The results show that the wind-induced vibrations may occur for the five segmental models of dual main cables with the maximum standard deviation of the amplitude up to 8.7 H. Evident differences in the vibration characteristics of the dual main cable can be observed under different wind direction angles and wind attack angles. The possible mechanisms of wind-induced instability of the dual main cables in construction phases are summarized as follows: the coupling mechanism of unstable main cable shape and aerodynamic interference between cables, the single mechanism of aerodynamic interference between cables, and the single mechanism of unstable main cable shape. At the early stage of the erection of the dual main cables, the wind-induced vibration of the cables is the most problematic, but the maximum amplitude of the dual main cables caused by instability decreases with the erection process pf the cables.

dual main cable  /  construction period  /  wind-induced instability  /  aerodynamic interference  /  wind tunnel test