Aerodynamic Stability of Ultra-Long Span Cable-Suspension Bridges

Suspension bridges are longest span structures, however, the major problem of those structures are its stability under wind loads. The stability of those bridges depends majorly on aerodynamic forces and structural supporting system; this study worked on those two major axes. Aerodynamic axis was to minimize aerodynamic forces by optimizing deck shape. Computational fluid dynamic (CFD) is an effective numerical tool for simulating flow around bridge deck, which was verified in the literature. six deck cross sections were studied – three elliptical deck shapes and three closed trusses-; their generated aerodynamic forces were compared with forces acting on Sutong Bridge and the best one was modelled as unsteady- state model for calculating flutter derivatives. The elliptical deck shape is found to generate the least static pressure and aerodynamic forces relative to the box and closed truss shapes; that proves, as deck shape get smoother aerodynamic forces generated by the deck reducesStructural axis was to improve the stability of cable supporting system. A combination of three-dimensional suspension cable and cable-stay systems studied. Catenary theory was improved for determining three-dimensional suspension cable profile. Three models suspension bridge and eight models cable-stayed suspension cable were studied. The use of three-dimensional suspension cable improved critical wind speed..