Wind Stability and Structural Optimization of a Three-Tower Cable-Stayed Suspension Bridge.

By using a computational procedure of three-dimensional aerostatic and aerodynamic stability analysis of long-span bridges, the dynamic characteristics, structural stability including the aerostatic stability and aerodynamic stability are first analyzed for a three-tower cable-stayed suspension bridge with main spans of 1400 m, then the parametric analysis is conducted, and finally a structural optimization scheme of the example bridge is proposed and confirmed numerically. The results show that the three-tower cable-stayed bridge has significant flexibility with less vertical and especially horizontal stiffness, and is sensitive to the transverse wind action; the three-tower cable-stayed bridge exhibits a coupled aerostatic instability pattern of vertical bending and torsion; the aerodynamic stability is worse than the aerostatic stability, the flutter critical wind speed is significantly reduced due to the static wind action, and thus the aerostatic effect must be involved in the aerodynamic stability analysis; the best wind stability is obtained for the example bridge as 2 auxiliary piers are set in each side span, the cable sag-to-span ratio is 1/6, the suspension-to-span ratio is 0.23, three pairs of cross hangers are set at the transition regions of the cable-stayed and suspension systems, and the girder depth is 4.5 m. [ABSTRACT FROM AUTHOR]