Effect of wind Load On High Rise Building

### Wind Loads per IS 875 Part 3

For plant structures designed under Indian codes, the program calculates the wind load per IS 875 Part 3 Wind Load on Buildings and Structures, Fourth Revision (2002). A static wind pressure is applied to the structure by the program using the following general procedure.

Calculate Basic Wind Speed, Vb, based on mapped values (Figure 1 in Section 5) or the table supplied in Appendix A of IS 875.
Calculate Probability Factor (risk coefficient), k1, from Table 1 in Section 5 of IS 875.
Calculate the k2 Factor (Table 2 in IS 875) based on structure height and terrain category. Separate k2 values are determined at different height intervals for vertical vessels as well as for each horizontal vessel in a stacked configuration.

Calculate the Topography Factor, k3 per Appendix C in IS 875.
Calculate the Design Wind speed for each height considered (IS 875, Clause 5.3) as:

Note: The cyclonic factor, k4, is typically not significant for foundations and is assumed as 1.0 by the program. However, the Cf value can be multiplied by the desired k4 value to effectively account for structures in cyclonic regions.
Calculate the wind pressure for each height considered (IS 875, Clause 5.4) as:

Calculate the design wind pressure for each height as:

Where:

Kd = wind directionality factor, as determined in Cl. 5.4.1.

Ka = area averaging factor, as determined in Cl. 5.4.2.

Kc = combination factor, taken from Table 19 in Section 6.

For each height, the exposure area, A, is consider. This area is calculated differently for vertical and horizontal vessels.

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