Nonlinear aerodynamic stability analysis of long-span suspension bridges during erection

Because the stiffening girder lacks torsional continuity, aerodynamic stability (flutter) of long-span suspension bridges during erection is often more problematic than in the final state. For long-span suspension bridges in erection, structural stiffness is much lower and large deformation occurs due to the dynamic wind action. It leads to the significant changes of the aerodynamic shape and structural dynamic characteristics. Therefore, nonlinear effects due to the large deformation will directly affect the aerodynamic stability of long-span suspension bridges. In this paper, numerical aerodynamic stability analyses are performed for the erection process of Yichang Suspension Bridge over Yangtze River by three-dimensional nonlinear flutter analysis, in which the nonlinearities of structural dynamic characteristics and aeroelastic forces caused by large deformation are fully considered. An interesting result is obtained that the bridge is more stable when the stiffening girder is erected in a non-symmetrical manner as opposed to the traditional symmetrical erection schedule. It also shows that the aerodynamic stability decreases severely due to the nonlinear effects. Therefore, the nonlinear factors should be considered accurately in aerodynamic stability analysis of long-span suspension bridges in erection.