Plain and Reinforced Concrete —
Code of Practice

Scope & Application

IS 456:2000 applies to the design of plain and reinforced concrete structures used in buildings and civil engineering works. It covers both the Limit State Method (primary) and the Working Stress Method (permitted only for specific cases). Cl. 1.1

The code does not cover:

• Prestressed concrete structures (see IS 1343)
• Liquid-retaining structures (see IS 3370)
• Concrete roads and pavements
• Mass concrete (e.g., dams)
• Specialised structures like nuclear containment vessels

Design Philosophy

IS 456 adopts the Limit State Design (LSD) approach, which ensures that a structure remains fit for use throughout its intended life by checking two primary limit states:

Partial safety factors are applied separately to loads (γ_f) and material strengths (γ_m) to account for uncertainties independently. Cl. 18.2

Grades of Concrete

Concrete is designated by its characteristic compressive strength (f_ck) at 28 days, expressed in N/mm². The prefix 'M' denotes the mix grade. Cl. 6.1, Table 2

Durability & Nominal Cover

Nominal cover is the design depth of concrete cover to all steel reinforcements, measured from the exposed surface to the outermost bar. It protects against corrosion and fire. Cl. 26.4, Table 16

For flat slabs, add 5 mm to the above values. The nominal cover should not exceed 75 mm for main reinforcement in beams and columns without secondary transverse steel near the face.

Modulus of Elasticity

The short-term static modulus of elasticity (E_c) for concrete is given by: Cl. 6.2.3.1

Calculated values for common grades:

For long-term loading, the effective modulus accounts for creep:

Limit State Design — General Provisions

IS 456 specifies partial safety factors for loads and materials that engineers must apply before performing any limit state check. Cl. 18.2

Partial Safety Factors for Loads (γ_f)

Partial Safety Factors for Materials (γ_m)

Therefore, the design strength of concrete = f_ck / 1.5 = 0.67 f_ck, and the design yield stress of steel = 0.87 f_y.

Flexure — Design of Beams

IS 456 uses a rectangular stress block for the compression zone in limit state flexure design. The stress block parameters are defined in Cl. 38.1.

Stress Block Parameters

Minimum & Maximum Steel

Shear & Torsion

Shear design ensures that the beam can resist transverse forces without diagonal tension failure. IS 456 provides nominal shear strength (τ_c) based on the percentage of tension steel and concrete grade. Cl. 40, Table 19

Key Shear Provisions

Minimum Shear Reinforcement

For solid slabs, minimum shear reinforcement may be omitted when V_u ≤ τ_c × b × d, provided the slab depth does not exceed 300 mm. Cl. 26.5.1.6 Note

Compression — Design of Columns

Columns are classified as short or long based on the slenderness ratio. Cl. 25.1.2

Key Column Provisions

Lateral Ties (Transverse Reinforcement)

For earthquake-resistant ductile detailing of columns, IS 13920 overrides these tie spacing requirements with much stricter confining hoop rules. See IS 13920 →

Slab Design

Slabs are classified based on the ratio of longer span (L_y) to shorter span (L_x):

Effective Span to Depth Ratios (Cl. 26.5.2)

These values are for Fe 415 steel. Multiply by 0.8 for Fe 500. Apply modification factors for actual steel percentage per Fig. 4 of IS 456. Cl. 26.5.2.1

Minimum Slab Steel

Bond, Anchorage & Lap Length

Development Length (L_d)

Where τ_bd = design bond stress:

Lap Length

Key Detailing Requirements

Hooks and Bends

Amendments Summary

Since publication in 2000, four amendments have been issued. Key changes include:

Related IS Codes

Codes frequently used alongside IS 456: