Long-span cable-stayed bridges exhibit some features which are more critical than typical long span bridges such as geometric and aerodynamic nonlinearities.A three-dimensional nonlinear fully-coupled analytical model is developed in this study to improve the dynamic performance prediction of long cable-stayed bridges under combined traffic and wind loads.The aerostatic and aerodynamic wind forces acting on the whole bridge including the bridge deck,pylon,cables and even piers are all derived.The dynamic interaction between vehicles and the bridge depends on both the geometrical and mechanical relationships between the wheels of vehicles and the contact points on the bridge deck.Nonlinear properties such as geometric nonlinearity and aerodynamic nonlinearity are fully considered.The equations of motion of the coupled wind-traffic-bridge system are derived and solved with a nonlinear separate iteration method which can considerably improve the calculation efficiency.A long cable-stayed bridge,Sutong Bridge across the Yangze River in China,is selected as a numerical example to demonstrate the dynamic interaction of the coupled system.The influences of the whole bridge wind field as well as the geometric and aerodynamic nonlinearities on the responses of the wind-traffic-bridge system are discussed.