For the purpose of calculating the wind pressure distribution around a cylindrical structure of circular cross-section, the value of external pressure coefficients given in Table 22 may be used, provided that the Reynolds number is more than 10 000. They may be used for wind blowing normal to the axis of cylinders having axis normal to the ground plane and cylinders having their axis parallel to the ground plane. 'h' is height of a vertical cylinder or length of a horizontal cylinder. Where there is a free flow of air around both ends, h is to be taken as half the length when calculating h/D ratio.
In the calculation of resultant load on the periphery of the cylinder, the value of shall be taken into account. For open ended cylinders, shall be taken as follows:
a) -0.8, where is more than or equal to 0.3; and
b) , where is less than 0.3.
4.5.3.3.8 Roofs and bottoms of cylindrical elevated structures
The external pressure coefficients for roofs and bottoms of cylindrical elevated structures shall be as given in Table 23. Alternately, the pressure distribution given in Fig. 3 can be used together with the force coefficients given in Table 28 for the cylindrical portion.