Earthquake zone factor and normalized design spectral acceleration for Indian sites (IS 1893 (Part 1):2025 §6.2)
◉ IS 1893 (PART 1):2025 §6.2 STYLE CHECK · NOT A REGULATORY SUBMISSION TOOL
⚠ Indicative tool only, and a general structural reference — not itself a tank calculator. IS 1893 Part 1 is India's general seismic hazard/design code, verified directly against this edition's page images. It has no dedicated storage-tank provisions of its own — those live in IS 1893 Part 2 (Liquid Retaining Tanks), which isn't available here, so this tool doesn't connect to the existing (US-code-based) Seismic Freeboard calculator; the two use incompatible parameter structures and shouldn't be cross-applied without that missing Part 2 bridge. What this does compute — the earthquake zone factor Z and normalized spectral acceleration ANH(T) — are foundational parameters useful for any structure type once Part 2 is available, or for general facility/structure seismic assessment in the meantime. The importance factor (I) and response reduction factor (R) needed to complete the design horizontal acceleration coefficient come from other clauses not verified in this pass — enter them yourself.
Identification
Research entries stay private to you for practice/testing. Switch to Official once this is a real design your company should see.
Earthquake Zone Factor Z (Tables 1–3, §6.2.2.2)
Structure category and design method determine the return period TR (Table 1 for LSM, Table 2 for WSM), which is then used to look up Z from Table 3. Category definitions (what counts as Special/Critical/etc.) are given elsewhere in the standard and aren't reproduced here — confirm your structure's category against the actual clause.
5% critical damping, equivalent static method. No spectrum is given for site class E — a site-specific hazard assessment is required instead (§6.3). Valid up to T=10.0s.
Result
Governing branch—
ANH,5%(TH)—
Design Horizontal Acceleration Coefficient (§6.2)
AHD = Z × I × ANH(TH) / R, from the base equation VBD,H = AHD W.