FLUTTER ANALYSIS OF SUPER LONG SPAN CABLE-STAYED BRIDGES INCORPORATING AERODYNAMIC FORCES OF STAY CABLES

With center span of cable-stayed bridges exceeding 1000m and the length of stay cables close to 600m, only inclusion in aerodynamic forces of main deck cannot reflect the actual situation of cable-stayed bridges' configuration to some extent during wind-resistant design. Consequently, the aerodynamic forces of stay cables should be considered in the three-dimensional flutter analysis of cable-stayed bridges. In this study, a multimode flutter analysis method developed by the second author is first described., Mathematic expressions of unsteady aerodynamic force of stay cable were then derived in terms of aerodynamic damping and stiffness matrices. Recognizing the variation of wind velocity along with the cable length and the reduced frequency as well, a Gaussian numerical integration scheme is used to numerically obtain the aerodynamic damping and stiffness matrices under a certain wind velocity at deck level. The above procedure is implemented into NACS by an independent module. As an example, the multimode flutter analysis of Sutong bridge was conducted by using NACS. Fair agreement is achieved between the present numerical simulation and wind tunnel test results, especially, when the aerodynamic derivatives of stay cables were taken as quasi-steady aerodynamic derivatives, aerodynamic force on cables is helpful to stabilize the bridge.