Abstract
This paper presents an experimental investigation on wind-induced vibrations of a suspension bridge with ultimate main span length, including flutter and buffeting. Since the upper limit of a suspension bridge’s main span can reach more than 5,000m based on strength and weight of steel main cables, a feasible prototype with a span arrangement of 2,000m+5,000m +2,000m has been proposed. In order to improve flutter stability, a twin box girder has been designed with a 40m slot in center and two 20m wide decks suspended by four main cables. Its full aeroelastic model was designed and manufactured with the geometrical scale of 1:620, and the wind tunnel testing was carried out under smooth flows and turbulent flows for different angles of attack. A big difference in critical flutter speed was found between the proposed slotted girder and corresponding slot-sealed girder, which verifies the necessity of a widely-slotted twin box girder for a super-long suspension bridge. Among three angles of attack, the critical flutter speed under smooth flow has the maximum value of 80.9 m/s at -3° and the minimum value of 51.4m/s at 3°. On-coming turbulence will not only cause buffeting responses but also influence the critical flutter speed in an unfavorable way.
Highlights
Ancient suspension bridges were built in China long before the Anno Domini, the construction of modern suspension bridges around the world has experienced a considerable development since 1883, when the first modern suspension bridge, Brooklyn Bridge, was built
Since anti-symmetric lateral and vertical modes participated during flutter, the aerodynamic instability of a 5,000 m-spanned bridge is classical flutter excited by modal coupling effect
A comparison of vibration amplitude shows the flutter under 3◦ was more violent, which may be related to gravitational stiffness losing for a positive attack angle
Summary
Ancient suspension bridges were built in China long before the Anno Domini, the construction of modern suspension bridges around the world has experienced a considerable development since 1883, when the first modern suspension bridge, Brooklyn Bridge, was built. It took about 48 years for the span length of suspension bridges to grow from 486 m of Brooklyn Bridge to 1,067 m of George Washington Bridge in 1931, as the first bridge with a span length over 1,000 m, and had a great increase factor of 2.2. With the ever-growing span length, suspension bridges are becoming longer, lighter and more flexible, and results in wind-induced vibrations, in particular flutter
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