IS 13920:1993 is the Indian Standard (BIS) for ductile detailing of reinforced concrete structures subjected to seismic forces - code of practice. This code provides mandatory requirements for detailing reinforced concrete structures to ensure ductile behavior during earthquakes. It focuses on specific rules for reinforcement in beams, columns, and joints, such as special confinement steel, 135-degree hooks, and splice locations. The primary goal is to prevent brittle failure and allow the structure to safely deform and dissipate seismic energy.
Provides provisions for ductile detailing of reinforced concrete buildings to ensure satisfactory performance during earthquakes (older version).
Quick Reference — IS 13920:1993 Ductile Detailing (legacy)
Ductile detailing of RCC structures for seismic forces — older edition. Hoop spacing, beam-column, splice rules.
| Reference | Value | Clause |
|---|
| Applicability — seismic zones | III, IV, V (mandatory) | Cl. 1.1.2 |
| Concrete minimum grade — flexural members | M20 | Cl. 5.2 |
| Concrete minimum grade — vertical members > 4 storey | M25 | Cl. 5.2 |
| Steel grade — minimum— 2016 edition mandates Fe500D | Fe415 (HYSD) | Cl. 5.3 |
| Beam — width minimum | 200 mm | Cl. 6.1.2 |
| Beam — depth/width ratio | ≤ 4 (preferably 1.5–2.0) | Cl. 6.1.3 |
| Beam — clear span / depth | ≥ 4 | Cl. 6.1.4 |
| Beam tension steel — minimum | 0.24 √fck / fy (= 0.205 % typical) | Cl. 6.2.1b |
| Beam tension steel — maximum | 2.5 % | Cl. 6.2.2 |
| Beam compression steel — minimum (at face) | 0.5 × tension steel | Cl. 6.2.3 |
| Beam stirrups — confining length each end | 2 d from face of support | Cl. 6.3.5 (a) |
| Beam stirrup spacing — confining zone | ≤ d/4 or 8 × bar diameter, whichever less | Cl. 6.3.5 (b) |
| Beam stirrup spacing — middle of span | ≤ d/2 | Cl. 6.3.5 (c) |
| Beam stirrup hook angle— 2016 retained 135° | 135° required (≥ 6d extension) | Cl. 6.3.5 |
| Column — minimum dimension | 200 mm (when reinforcement laps occur) | Cl. 7.1.2 |
| Column — minimum aspect ratio | 0.4 (shorter side / longer) | Cl. 7.1.3 |
| Column longitudinal steel — minimum | 0.8 % | Cl. 7.2.1 (refers IS 456) |
| Column — maximum reinforcement | 6 % (4 % at lap) | Cl. 7.2.2 (refers IS 456) |
| Column — confining hoop spacing— tightened in 2016 | ≤ ¼ × least lateral dimension or 100 mm | Cl. 7.4.6 (b) |
| Column — confining length end zone | ≥ depth, L/6, or 450 mm (whichever max) | Cl. 7.4.1 |
| Beam-column joint — design shear— fully recodified in 2016 | from beam yielding (capacity design) | Cl. 8.2 |
⚠ Superseded by IS 13920:2016 with significant tightening (closer hoop spacing, capacity-design joint, Fe500D mandate). New construction must use 2016. This entry is for assessment of legacy structures designed under 1993.
Overview
- Status
- Superseded — superseded by IS 13920:2016
- Usage level
- Essential
- Domain
- Structural Engineering — Disaster Resilience and Retrofitting
- Type
- Code of Practice
- Amendments
- Amendment No. 1 (August 1994); Amendment No. 2 (December 1995)
Also on InfraLens for IS 13920
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! This version has been superseded by IS 13920:2016, which has significant changes. It is crucial to use the latest version for new designs.
! The 135-degree hook on stirrups and ties is a critical requirement for ductility and is a common point of failure during site inspection if not followed.
! Lap splices are strictly prohibited within plastic hinge zones (near beam-column junctions) and must be located in the central half of the member with close confinement ties.
Frequently referenced clauses
Updates & Amendments2 amendments
Amendment No. 1 (August 1994)
Amendment No. 2 (December 1995)
Consolidated list per BIS. For the text of each amendment, refer to the BIS portal link above.
reinforced concretesteelductile detailing
International Equivalents
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International Comparison — Coming Soon
We're adding equivalent international standards for this code.
Key Values7
Quick Reference Values
Minimum Grade of ConcreteM20
Minimum Column Dimension200 mm
Stirrup Hook Angle in Seismic Zone135 degrees
Stirrup Hook Extension Length10 times bar diameter (min 75 mm)
Maximum stirrup spacing in confinement zone (Beams)d/4 or 100 mm
Strong Column-Weak Beam Capacity Ratio1.1
Maximum percentage of steel in column6% (4% recommended for lapping)
Key Formulas
ΣMc ≥ 1.1 ΣMb — Strong Column-Weak Beam check
Tables & Referenced Sections
Key Clauses
Clause 5.1 - Minimum Grade of Concrete (M20)
Clause 6 - Flexural Members (Beams)
Clause 7 - Columns and Frame Members
Clause 7.2 - Strong Column-Weak Beam Requirement
Clause 8 - Special Confining Reinforcement
Frequently Asked Questions4
What is the minimum grade of concrete allowed by this code?+
M20 grade concrete is the minimum specified (Clause 5.1).
What is the 'Strong Column-Weak Beam' concept?+
The sum of moment capacities of columns at a joint must be at least 1.1 times the sum of moment capacities of beams framing into it, to ensure failure occurs in beams rather than columns (Clause 7.2).
What are the requirements for stirrup hooks for seismic resistance?+
Stirrups must have a 135-degree hook with a 10-diameter extension (minimum 75mm) at the end (Clause 8.1 b).
Where are lap splices for longitudinal bars in columns permitted?+
Lap splices are only permitted in the central half of the column length, not at the top or bottom ends (Clause 7.3.2).
QA/QC Inspection Templates
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QA/QC templates coming soon for this code.