Experimental study on features and control of wind-induced instability of parallel dual main cables of ultra-long-span suspension bridge in construction phases

Abstract

During the construction phase of single-sided parallel double main cables without the constraint of hangers, the low frequency of the main cables and the continuous variation in their cross-sectional shape make them highly susceptible to harmful wind-induced vibrations under commonly encountered wind speeds. In this study, the features of wind-induced vibration of parallel dual main cables in construction phases and the effectiveness of different countermeasures were studied by using wind tunnel tests. Firstly, based on the design scheme of single-side parallel dual main cables for a large-span suspension bridge with a main span of 2180 m, five segmental models of typical cross-sectional shapes of dual main cables during the construction phase were manufactured. Subsequently, a series of vibration measurement wind tunnel tests were carried out to obtain the wind-induced responses of the dual main cables under typical construction cases. Then, the aerodynamic damping of representative vibration cases was identified to explore the instability mechanism. The results indicate that wind-induced vibrations of dual main cables during the construction phase primarily manifest in three forms: vibration of the upstream main cable only, vibration of the downstream main cable only, and simultaneous vibration of both upstream and downstream main cables. The aerodynamic damping characteristics vary significantly among these different vibration modes. Finally, the effectiveness of four countermeasures was experimentally studied, including adjusting the spacing between the dual main cables and the construction progress, wrapping the cables with temporary plastic film and increasing structural damping. The results indicate that, compared to the other three countermeasures, the asynchronous construction of the two main cables demonstrates the greatest potential in mitigating wind-induced instability.