IS 1893:2014 Part 2 is the Indian Standard (BIS) for criteria for earthquake resistant design of structures - liquid retaining tanks - elevated and ground supported. This standard provides criteria for the earthquake-resistant design of elevated and ground-supported liquid retaining tanks. It utilizes a two-degree-of-freedom spring-mass model to calculate the impulsive (liquid moving with tank) and convective (sloshing) hydrodynamic effects during seismic events.
Specifies criteria for the earthquake resistant design of elevated and ground-supported liquid retaining tanks.
Two-mass model, impulsive / convective parameters, R-values for tanks, damping and free-board.
| Reference | Value | Clause |
|---|---|---|
| Scope | Liquid retaining tanks (ground-supported & elevated) | Cl. 1 |
| Two-mass spring model — components | Impulsive (mi) + convective (mc) | Cl. 4.2 |
| Importance factor I — drinking water / fire-fighting | 1.5 | Cl. 4.4 (Table 1) |
| Importance factor I — tanks containing hazardous liquid | 1.75 | Cl. 4.4 (Table 1) |
| Importance factor I — industrial tanks (general) | 1.0 | Cl. 4.4 (Table 1) |
| Response reduction R — RC ground-supported | 2.0 (uncracked) / 1.8 (cracked) | Cl. 4.5 (Table 2) |
| Response reduction R — Steel ground-supported | 2.5 | Cl. 4.5 (Table 2) |
| Response reduction R — Elevated tank (frame staging) | 1.8 (ordinary) / 2.5 (ductile) | Cl. 4.5 (Table 2) |
| Response reduction R — Elevated tank (shaft staging) | 1.5–1.8 | Cl. 4.5 (Table 2) |
| Damping — convective mode | 0.5 % | Cl. 4.5.1 |
| Damping — impulsive mode (RC / steel) | 5 % / 2 % | Cl. 4.5.1 |
| Time period — impulsive (rectangular) | Ti = 2π √(d / g · ψ) — see Annex C | Annex C |
| Time period — convective | Tc per Annex C (rectangular & circular) | Annex C |
| Free board — sloshing wave height | ≥ d_max sloshing (typ. 0.3–0.6 m) | Cl. 4.11 |
| Vertical seismic component | (2/3) × horizontal | Cl. 4.10 |
| Hydrodynamic pressure distribution | Per Annex D (Housner / EC8 method) | Annex D |