Effect of building length on wind loads on low-rise buildings with a steep roof pitch

A wind tunnel model study was carried out on long, low-rise buildings with a steep roof pitch to determine the effect of the length-to-span aspect ratio on the external wind pressure distributions. The study showed a significant increase in the magnitude of the negative pressure coefficients on the leeward roof and wall, with an increase in aspect ratio, for oblique approach winds. These large suction pressures also generate large design wind load effects on the frames near the gable-end. The 1989 edition of the Australian standard for wind loads, AS 1170.2-1989 was found to underestimate the wind loads on steep pitch gable-roof buildings of aspect ratio greater than 3, on areas near the windward gable-end, and hence the critical bending moments in the supporting structural frames. The current Australian/New Zealand wind load standard, AS/NZS 1170.2-2002 specifies increased negative pressure coefficients on the leeward half of high pitch roof buildings, and critical bending moments in the supporting frames calculated from these distributions agree quite well with values obtained from the wind tunnel study. However, other major standards severely underestimate the critical bending moments, and the effective pressure coefficients producing those bending moments, especially on the leeward roof slope.