Low-rise buildings - Wind Loading of Structures - page 213

moment were discussed in Chapter 5. The effective static pressure distribution so
determined must lie between the extreme point pressure limits of the pressures around the
frame, as shown in Figure 8.18.
It is of interest to consider the distributions of pressure coefficients given in wind
codes and standards. Usually an 'envelope' loading is specified with pressures uniformly
distributed in length along the columns and rafters, as shown in Figure 8.16. These are
Figure 8.18 Peak load distribution for a corner
bending moment (Holmes and Syme, 1994).
usually, but not always, conservative loadings which will give overestimates of load
effects such as bending moments.
8.4.3 Hipped roof buildings
It has been observed that, on several occasions in damage investigations following severe
wind storms, hipped roof buildings have generally suffered lesser damage. Meecham et
al. (1991) studied wind pressures on hipped and gable roof buildings of 18.4° pitch in a
boundary-layer wind tunnel. Although there is little difference in the largest peak total lift
force, or overturning moment, on the two roofs, the gable end region of the gable roof
experiences around 50% greater peak negative local pressures, than does the
corresponding region on the hipped roof. Furthermore the largest area-averaged full-span
truss load was about twice as high on the gable roof.
However, Xu and Reardon (1998), who studied pressures on hipped roofs with three
different roof pitches (15°, 20° and 30°), found that the benefits of a hipped configuration
compared with a gable roof type reduces as the roof pitch increases. Figure 8.19 shows