For structures of various plan shapes other than rectangular plan shape, the external pressures acting on the projected area in the plane perpendicular to the wind, should be the product of the basic pressure (p) given above and thc shape factors given in Table 1.4.
TABLE 1.4. PLAN SHAPE FACTORS
thereof, having due regard to the level of mean retarding surface and variation in wind pressure with height. In making calculations, due regard should be given to shape factor and internal air pressure.
The stability calculations of the building as a whole shall be done considering the combined effect, as well as separate effects of imposed loads and wind loads on vertical surfaces, roofs and any other part of the building above the general roof level.
Calculations shall be made for the effect of wind on the design of individual components of the building. Where, however, adequate stiffering is provided by walls, or floors and walls, calculations for the effecas of wind, except in regard to wind panels, roofs amd foundations, need not be made on:
(a) A building or part of a building of which the heigh h does not exceed twice the effective widths,
(b) a section adjoining two parts of an adequately stiffened building, if height of the section exceeds twice its width but the length of the section does not exeed four times its width, and
(c) a wing of such a building if it does not project more than twice its own width.
In the case of sloped roofs, the wind pressure varies with the degree of slope. The slope of the roof towards the wind direction is known as the windward slope, while the slope to the other side of the wind direction is
known as the leeward slope. For flat and pitched roofs, the wind pressures normal to the surface, due to wind blowing at right angles to the ridge, in terms of basic wind pressure(p) are given in Table 1.5.
TABLE 1.5. WIND PRESSURE ON ROOFS (WIND NORMAL TO RIDGE)