Civil Engineering Reference
In-Depth Information
In tall and flexible buildings, aerodynamic behaviour generally becomes important.
The wind-induced building response of tall buildings can be reduced by means of
aerodynamic-based design and modifications that change the flow pattern around the
building or break up the wind affecting the building face.
Aerodynamic-based design can be divided into two types, “aerodynamic architec-
tural design” and “aerodynamic architectural modifications” and their subgroups.
Aerodynamic architectural design
Aerodynamic architectural design is realized by taking into consideration matters
such as “building orientation (position)”, “aerodynamic form”, “plan variation” and
“aerodynamic top” as part of the basic design. Aerodynamic architectural design plays
an important role in reducing the effect of wind on tall buildings (Ali and Armstrong,
1995; Holmes, 2001; Irwin, 2009; Irwin et al., 2006; Irwin et al., 2008a; Irwin et al.,
2008b; Kareem et al., 1999; Schueller, 1977; Scott et al., 2005). This reduction is
generally in the region of 20-30 per cent, but can even exceed 50 per cent (Kim et
al., 2008; Scott et al., 2005). These approaches are described below.
Building orientation (position)
Orienting (positioning) the building according to the prevailing wind direction is an
effective design approach for reducing wind loads. A reduction of between 10-20 per
cent of the across-wind building response can be obtained by rotating the building to
within 10º of the wind direction (Scott et al., 2005). The effectiveness of this approach
is dependent on both the wind climate at the project site and the shape of the
building. In wind climates with very directional extreme winds and building shapes
that are directionally sensitive this is more effective than, say, for a more regularly
shaped building in a wind climate without strong directional characteristics.
Aerodynamic form
The use of aerodynamic building forms is an effective method of reducing the wind
loads on buildings. In this context, cylindrical, elliptical, conical and twisted forms
can be accepted among the efficient building forms.
Because cylindrical buildings (i.e., having circular or elliptical plan forms) have a
smaller surface perpendicular to the wind direction, the wind pressure is less than in
prismatic buildings. For buildings having circular plan form, the wind load is about
20 per cent less, compared with buildings having a rectangular plan form (Taranath,
2005). According to Davenport's study (1971) of models representing buildings of
about 70 stories, the largest lateral drift value exhibited by a building with a circular
plan under wind loads is approximately half of the lateral drift value exhibited by
a building with a square plan. Buildings with elliptical plans also exhibit similar
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