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Cable-supported bridges such as suspension bridges and
cable-stayed bridges are lightand slender structures. When
excited by wind gust loads, these structures can fail
byaerodynamic instability, especially, in the form of flutter
instability. The flutterinstability is a self-excited
oscillatory motion, which is caused mainly by the self-
excitedaerodynamic forces induced by the fluid-structure
interaction, when a structure is exposedto air flows at critical
speeds. In response to the continuous build-up of the input
energy,the motion of the structure increases in amplitude and
becomes unstable. The purpose of thispaper is to establish a
general three-dimensional theory for analyzing the flutter
instabilityof cable-stayed bridges. The equation of motion for
the structure is transformed by the statespace method into a
characteristic equation, from which the eigenvalues solved are
usedto judge the aeroelastic stability. Major features of the
present theory include: (1) Thegeometric nonlinearities
associated with the main girders, pylons, and cables are all
takeninto account. (2) The joint equilibrium conditions
violated by traditional beam elements atthe deformed state are
enforced by using a rigid body-qualified beam element. (3)
Theinteraction between the fluid and structure is considered
through the flutter derivatives. Theresults computed herein are
shown to be rather accurate when compared with those obtainedby
other methods.
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