Civil Engineering Reference
In-Depth Information
Figure 12.6
Measured critical flutter speeds
and comparisons with the Selberg prediction
formula (Wardlaw, 1971).
12.3.3
Buffeting of long-span bridges
A bridge that is otherwise stable in flutter up to a high wind speed and does not suffer
from vortex-induced vibrations at low wind speeds will still experience dynamic response
to atmospheric turbulence, known as
buffeting,
over a wide range of wind speeds. This
response will normally determine the size of the structural members and require
evaluation at the design stage.
Davenport (1962) was the first to apply random vibration methods to the buffeting of a
long-span suspension bridge. These methods were later validated by comparison with
model studies in turbulent boundary-layer flow in the 1970s (e.g. Holmes, 1975, 1979;
Irwin, 1977).
The methodology described in Section 5.3.6 for the along-wind response of distributed
mass structures can be adapted to the
cross-wind
response of bridge decks excited by
vertical turbulence components.
The sectional cross-wind force per unit span can be written, applying a 'strip'
assumption:
(12.6)
