Design horizontal seismic coefficient, convective time period, and impulsive base shear for liquid retaining tanks (IS 1893 (Part 2):2014)
◉ IS 1893 (PART 2):2014 §4.4–4.6 STYLE CHECK · NOT A REGULATORY SUBMISSION TOOL
⚠ Indicative tool only, and this is the tank-specific document the Part 1 calculator flagged as missing. This 2014 edition (Fifth Revision) references IS 1893 Part 1:2002 for Z, Sa/g and the response spectrum — NOT the 2025 Part 1 edition already built into the separate IS 1893 Seismic Parameters calculator. Don't feed that tool's Z/ANH outputs directly into this one; enter Z and Sa/g here per this standard's own 2002-vintage references (or your project's governing edition) instead. Deliberately narrow in scope: covers §4.4–4.6 for ground-supported circular/rectangular tanks only. Not covered — elevated tanks, the impulsive time period Ti, convective base shear Vc, sloshing wave height, overturning moments, and hydrodynamic pressure distributions, all present in this standard but not verified in this pass.
⚠ One formula worth double-checking against your own copy. §4.3.2.1 prints Tc = Cc√(D/ρ), using ρ = mass density of liquid (as explicitly defined in this standard's own symbol list, confirmed by zooming into the source page twice). This differs from the more internationally common Housner-type sloshing period formula (used in, for example, API 650 Appendix E, already built into this project), which uses g (gravitational acceleration) in that position instead of density — those two quantities don't have the same units. We could not resolve this discrepancy with full confidence from the source alone; the formula is applied below exactly as printed, with ρ entered as mass density. Verify against your own edition before relying on the calculated period.
Identification
Research entries stay private to you for practice/testing. Switch to Official once this is a real design your company should see.
Design Horizontal Seismic Coefficient (§4.5)
Convective damping is fixed at 0.5% for all tanks/liquids (§4.4). Damping multiplier on Sa/g: 1.0 at 5%, 1.4 at 2%, 1.75 at 0.5% (§4.5.2).
Result
Damping used—
Damping multiplier—
Adjusted Sa/g—
Design horizontal seismic coefficient Ah—
Convective Mode Time Period (§4.3.2.1–.2)
Fig. 5 (circular, vs h/D) and Fig. 7 (rectangular, vs h/L) are graphs, not tables — read Cc off the chart for your tank's aspect ratio and enter it manually.
Result
Convective time period Tc—
Base Shear — Impulsive Mode, Ground-Supported Tank (§4.6.1)
Vi = (Ah)i × (mi + mw + mt) × g. Uses the impulsive Ah computed above — set Mode to Impulsive in the coefficient card first.