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).

IS 13920

: 1993

Ductile Detailing of Reinforced Concrete Structures Subjected to Seismic Forces - Code of Practice

SupersededEssentialCode of PracticeBIMStructural Engineering · Disaster Resilience and Retrofitting

Superseded by IS 13920:2016

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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 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

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This version has been superseded by IS 13920:2016, which has significant changes.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.