Nonlinear aerostatic stability analysis of suspension bridges

Nonlinear aerostatic stability analysis of long-span suspension bridges is studied by including directly the three combined effects of: (1) nonlinear three-component displacement-dependent wind loads, (2) geometric nonlinearity, and (3) material nonlinearity. The nonlinear three-component displacement-dependent wind loads are included through the static aerodynamic coefficients as a function of angle of attack. The various structural bucklings, such as flexural buckling, torsional buckling and flexural-torsional buckling, are considered using the element geometric stiffness matrix. Material nonlinearity is controlled using the concentrated plastic hinge model. The analytical modeling of wind-induced aerostatic instability is formulated using the finite-element method, taking into account the three components of displacement-dependent wind load as well as geometric and material nonlinearities. The numerical examples are performed on a three-dimensional finite-element model of the Akashi Kaikyo Bridge with a main span length of 1990 m. The results show that the aerostatic instability of the long-span suspension bridge is caused by the three combined effects. The results also indicate that the critical wind velocity for nonlinear aerostatic instability is significantly lower than the elastic flutter velocity.