IS 875 Part 3 Wind Load Calculator

Project metadata

Project nameProject numberStructure name / refClientDesigned byChecked byDateRevision

Wind speed

Cl. 6.3 · Annex A · Tables 1 & 2

City / town77 Annex-A locationsManual Vb override (m/s)Leave blank to use the city value. If entered, it wins.

Vb = 47.0 m/sAnnex A / Fig. 1 — Delhi

Class of structureTable 1 — governs k1Terrain category

Category 1Open terrain with few or no obstructions — open sea coasts, flat treeless plains.Category 2Open terrain with scattered obstructions 1.5–10 m high — airfields, open parkland, sparse undeveloped outskirts.Category 3Terrain with numerous closely spaced obstructions up to 10 m — well-wooded areas, towns, industrial suburbs.Category 4Terrain with numerous large, tall, closely spaced obstructions — large city centres, well-developed industrial complexes.

Table 2 — surface roughness

Reference height z (m)Cyclonic region categoryCl. 6.3.4 — governs k4

IS 875 (Part 3) has no soil-type input. Wind loading is governed by terrain category (surface roughness) and topography (upwind slope). Soil classification belongs to IS 1893 for seismic design.

Topography and pressure factors

Annex C · Cl. 7.2.1 · Cl. 7.3.2

Direct entry Annex C helper

Topography factor k3The value used in the calculation

Wind directionality KdCl. 7.2.1 — default 0.90Combination factor KcCl. 7.3.3.13 — 0.90 permitted

Openings / permeabilityCl. 7.3.2 — sets Cpi

Cpi = ±0.20