Study On The Wind Stability Of Super Long-Span Cable-Stayed Bridges

The building of Sutong Changjiang Bridge means the application of cable-stayed bridges has entered a new era when the main span is over1000m. To meet with the requirement of building the strait-crossing projects in the21st century, the span record of cable-stayed bridges has been refreshed constantly. Meanwhile, the bridge tower has been increasingly high, and structural stiffness of the bridge has declined greatly. As a result, the wind stability has become an important problem for the design and construction of super long-span cable-stayed bridges. This paper gives a comprehensive analysis and study on dynamic characteristics, aerostatic stability and aerodynamic stability of a super long-span cable-stayed bridge whose main span is1400m. The wind stability of super long-span cable-stayed bridges is investigated, and also the key design parameters and their reasonable values are also pointed out. The results provide helpful guide for the wind-resistant design of super long-span cable-stayed bridges.The finite element analysis software MIDAS and finite element analysis program of three-dimensional nonlinear aerostatic and aerodynamic stability analysis of long-span bridges are used respectively to analyze dynamic characteristics, aerostatic and aerodynamic stability of a super long-span cable-stayed bridge whose main span is1400m, and the results are compared with those of a suspension bridge whose main span is1385m, and considering from the aspect of wind stability, the availability of using super long-span cable-stayed bridge in long-span bridge with main span over1000m is discussed. In addition, the influence of structural design parameters including the height and width of the girder, the structure style of bridge tower, the height-span ratio of bridge tower, the ratio of side span to main span, the auxiliary piers in the side spans and the anchorage of stayed cables etc on the dynamic characteristics, aerostatic and aerodynamic stability of super long-span cable-stayed bridges are analyzed, and the key design parameters are pointed out, and also their reasonable values arc proposed.The results show that1)as compared to the suspension bridges with the same main span, the cable-stayed bridges have greater structural stiffness, and become more stable under the wind action, and consequently become favorable to be applied in super long-span bridges whose main span is over1000m;2) the super long-span cable-stayed bridges become more aerostatically and aerodynamically stable under the cases that the girder’s height is increased, the girder’s width is decreased, the inverted y-shaped bridge towers are used, the tower’s height is increased, the side span length is shortened, the auxiliary piers are installed in side spans and the partial stayed cables are earth-anchored.