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.
Quick Reference — IS 1893 Part 2:2014 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 |
⚠ Cross-references IS 3370 for RC water tanks. Project-specific sloshing checks require detailed wall/roof analysis.
Overview
- Status
- Current
- Usage level
- Specialized
- Domain
- Structural Engineering — Disaster Resilience and Retrofitting
- Type
- Code of Practice
Also on InfraLens for IS 1893
Practical Notes
! Base shear and moment must be calculated separately for impulsive and convective modes, then combined using the SRSS method.
! Ensure adequate freeboard is provided based on the calculated maximum sloshing wave height to prevent uplift or damage to the tank roof.
! The convective (sloshing) mass always has a very low damping ratio (0.5%), requiring specific spectral acceleration values.
Frequently referenced clauses
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International Equivalents
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International Comparison — Coming Soon
We're adding equivalent international standards for this code.
Key Values6
Quick Reference Values
Damping for convective (sloshing) mode0.5%
Damping for impulsive mode (concrete tanks)5%
Damping for impulsive mode (steel tanks)2%
Importance Factor (I) for drinking water/firefighting tanks1.5
Importance Factor (I) for other liquid tanks1.0
Response Reduction Factor (R) for RC SMRF elevated tanks2.5
Key Formulas
V = sqrt(Vi^2 + Vc^2) — Total design base shear combined using SRSS
Ah = (Z/2) * (I/R) * (Sa/g) — Design horizontal seismic coefficient
dmax = (Ah)c * R * Rc — Maximum sloshing wave height
Tables & Referenced Sections
Key Tables
Table 1 - Importance Factor (I)
Table 2 - Response Reduction Factor (R)
Key Clauses
Clause 4.2 - Spring Mass Model for Seismic Analysis
Clause 4.3.1 - Impulsive and Convective Mass
Clause 4.3.2 - Time Period
Clause 4.4 - Base Shear and Base Moment
Clause 4.5 - Hydrodynamic Pressure
Clause 4.7 - Sloshing Wave Height
Frequently Asked Questions4
What is the damping ratio for the sloshing liquid?+
0.5% for all types of liquids, regardless of the tank material.
How is the total base shear calculated?+
By combining the impulsive base shear (Vi) and convective base shear (Vc) using the Square Root of Sum of Squares (SRSS) method.
What Importance Factor should be used for municipal drinking water tanks?+
1.5, as they are considered essential post-earthquake lifelines (Table 1).
Why is freeboard critical in seismic design of tanks?+
To accommodate the sloshing wave height (dmax) generated during an earthquake, preventing excessive hydrodynamic pressure on the roof.
QA/QC Inspection Templates
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QA/QC templates coming soon for this code.