Study On Wind Stability Of Long-Span Suspension Bridge Under Construction

With the development of economy, long and super long-span bridges are urgently needed to be built in the intercontinental, strait-crossing and island-linking engineering projects. Because of its good spanning capacity and elegancy in appearance, suspension bridge has become the first choice for large-span bridges. As the span increases, suspension bridge becomes more susceptive to the wind action, particularly under construction. Because the bridge has not yet formed the final structural system during construction stages, structural stiffness is less, and structural stability under the wind action becomes more prominent. Therefore the wind stability of the bridge under construction becomes an important factor influencing the construction and design of suspension bridges. In this dissertation, taking the Xihoumen Bridge between Zhoushan Island and the mainland, under the sequences of the deck erected symmetrically from the midpoint of center span to the two pylons(midspan to pylons), from the two pylons toward the midpoint of center span(pylons to midspan) and simultaneously from the two pylons and the midpoint of center span toward the quarter points of center span(four working fronts) respectively, the effect of deck erection sequence on the wind stability of asymmetric suspension bridge is investigated numerically, and the favorable deck erection sequence with good wind stability is discussed. The results have good reference value and engineering guidance to the construction of similar large-span suspension bridges.In this dissertation, firstly, dynamic behavior of the bridge in the completion and under construction is analyzed by the computer program SDCA, which is based on the subspace iteration method. Secondly, using the computer program BSNAA for 3D structural nonlinear aerostatic analysis, evolution of aerostatic stability with deck erection is investigated numerically. Finally, by using the computer program BSFA for bridge structural flutter analysis, evolution of aerodynamic stability with deck erection is investigated numerically. The results show that: (1) the greatest structural frequencies and better aerodynamic stability are achieved under the deck erection sequence of midspan to pylons, whereas the best aerostatic stability is achieved under the deck erection sequence of pylons to midspan. The aerostatic and aerodynamic stability is the worst under the deck erection sequence of the four working fronts; (2) with comparison to the aerostatic stability, the aerodynamic stability of the bridge under construction is much worse. On the whole, the deck erection sequence of midspan to pylons seems to be more favorable with respect to the wind stability.