Civil Engineering Reference
In-Depth Information
For the isolated building, similar coefficients of variation occurred, but in this case, they
resulted from variation due to
wind direction
.
8.5
Multi-span buildings
The arrangement of industrial low-rise buildings as a series of connected spans is
common practice for reasons of structural efficiency, lighting and ventilation. Such
configurations also allow for expansion in stages of a factory or warehouse.
Wind-tunnel studies of wind pressures on multi-span buildings of the 'saw-tooth' type
with 20° pitch were reported by Holmes (1990b), and by Saathoff and Stathopoulos
(1992) on 15° pitch buildings of this type. Multi-span gable roof buildings were studied
by Holmes (1990b) (5° pitch), and by Stathopoulos and Saathoff (1994) (18° and 45°
pitch). The main interest in these studies was to determine the difference in wind loads
for multi-span buildings, and the corresponding single-span monoslope and gable roof
buildings, respectively.
As for single-span buildings, the aerodynamic behaviour of multi-span buildings is
quite dependent on the roof pitch. Multi-span buildings of low pitch (say less than 10°)
are aerodynamically flat, as discussed in Section 8.3.3. Consequently, quite low mean
and fluctuating pressures are obtained on the downwind spans, as illustrated in Figure
8.20. The pressures on the first windward span are generally similar to those on a single-
span building of the same geometry.
For the gable roof buildings and for the saw-tooth roof with the roofs sloping
downwards away from the wind, the downwind spans experience much lower magnitude
negative mean pressures than the windward spans. For the opposite wind direction on the
saw-tooth configuration, the highest magnitude mean pressure coefficients occur on the
second span downwind, due to the separation bubble formed in the valley.
