Civil Engineering Reference
In-Depth Information
14
Other structures
14.1
Introduction
In this chapter the wind loads on some structures not covered in Chapters 8-13, and
appendages attached to buildings, will be considered. Some of these structures may be of
lesser economic importance, but are often sensitive to wind loads, fail early during a
severe wind storm and provide a source of flying debris.
In the following sections wind loads on free-standing walls (including noise barriers
along freeways or motorways) and hoardings are discussed. Free-standing paraboloidal
antennas for radio telescopes and antennas of various geometries attached to towers or
buildings are considered. Wind loading of free-standing roofs or canopies, solar panels
attached to the roofs of buildings, as well as appendages attached to buildings such as
canopies, awnings and balconies, are also discussed.
14.2
Walls and hoardings
14.2.1
Single walls under normal and oblique winds
In Sections 4.3.1 and 4.3.2, the mean drag coefficients on walls on the ground are
discussed in the context of bluff-body aerodynamics. Discussion of wind loads on free-
standing walls under normal and oblique winds will be expanded in this chapter.
In Figure 14.1, mean and maximum net pressure difference coefficients acting on
complete walls of various breadth/height ratios are shown plotted. These values are based
on boundary-layer wind-tunnel measurements (Letchford and Holmes, 1994) in open
country terrain (Jensen numbers
h/z
0
in the range 50-160). The net pressure coefficient,
C
pn
is defined in Equation (14.1) and, in this case, is equivalent to a drag coefficient:
(14.1)
where
p
w
is the area-averaged pressure coefficient on the windward face of the wall,
p
L
the area-averaged pressure coefficient on the leeward face of the wall and Ūh is the mean
wind speed at the top of the wall.
The maximum values were expected values for periods equivalent to 10 m in in full
scale. The mean net pressure coefficients show a small reduction in the range of
b/h
from
0.5 to 5, as previously shown in Figure 4.5. A larger reduction occurs for the maximum
pressure coefficients—this is due to the reduction in spatial correlation for longer lengths
