Flutter performance of a double-main-span suspension bridge during erection with temporary constraints on girders

Abstract

An increasing number of double-main-span suspension bridges with three towers are now constructed. For this bridge type, close modes exhibits similar characteristics due to the participation of two main and side spans, which is more prominent during girder erection as different spans are disconnected. It is important but hard to accurately determine the modal combination for flutter analyses. In this paper, full-order modal flutter analyses were performed to study the flutter performance of a double-main-span suspension bridge during erection. The dominating modal branches for the anti-symmetrical and symmetrical flutter instability were determined, respectively. After that, temporary pier constraints on the side spans and temporary connections between girder segments were set, respectively, to study the flutter suppression. The results show that the anti-symmetrical flutter instability of the bridge during erection is prior to the symmetrical one except for the first two stages. Reinforcing the connections between girder segments in the lateral direction could significantly improve the anti-symmetrical flutter stability. Meanwhile, the symmetrical flutter instability of the bridge during erection is more complicated as it is associated with the girder torsion, cable swing, and girder lateral bending. The set of temporary pier constraints or proper temporary connections is favorable.