Study On Wind Stability Of Cable-Stayed Suspension Bridge Under Construction

Cable-stayed suspension bridge is the combination of cable-stayed bridge and suspension bridge, has advantages of both the cable-stayed bridge and suspension bridge, with beautiful outline, optimum structural performance and economy. Cable-stayed suspension bridge has great development prospect. But as the bridge span increases, the bridge becomes more sensitive to the wind action, especially during the construction phase. As the final structural system is not formed during the construction phase and the structural rigidity is low, structural stability under wind action is even more prominent. In this work, by taking a design alternative of cable-stayed suspension bridge as example, the effect of different deck erection sequence on wind stability of the cable-stayed suspension bridge is investigated numerically and also the deck erection methods with good wind stability is proposed, which has a good reference value and engineering significance for the future construction of cable-stayed suspension bridge.Firstly, by using MIDAS software and self-programming software, the ideal states of the bridge in completion and under construction are analyzed, and the corresponding finite element models of all construction stages are established; Secondly, by using the computer program SDCA based on the subspace iteration method, structural dynamic characteristics of the bridge during the whole construction process under two different deck erection sequences is analyzed. Thirdly, by using the computer program BSNAA for 3D structural nonlinear aerostatic analysis, the evolution of structural aerostatic stability during the whole construction process under two different deck erection sequences is investigated, and the influence of deck erection sequence on the aerostatic stability is revealed; Finally, by using the computer program BSFA for bridge structural flutter analysis, the evolution of structural flutter stability during the whole construction process under two different deck erection sequences is investigated, and the influence of deck erection sequence on structural flutter stability is revealed.The results show that: (1) the bridge has higher natural frequencies and better wind stability as the deck erection starts simultaneously from the two pylons to the midspan in center span, and in side span, it starts from the pylons to the bridge end; (2) as the deck is erected simultaneously from the midspan and the two pylons toward the junction of the cable-stayed and suspension segments, structural dynamic characteristics and the aerostatic stability change smoothly, and however structural flutter stability increases gradually during the construction phase. Therefore, the deck erection sequence of pylons to midspan seems to be more favorable with respect to the wind stability.