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IS 811:1987 is the Indian Standard (BIS) for cold formed light gauge structural steel sections –. IS 811 specifies the dimensions, weights, and cross-sectional properties of cold-formed light gauge structural steel sections like angles, channels, Z-sections, and hat sections. Engineers and detailers use this code to select standard profiles for lightweight structural framing, such as roof purlins and wall girts.
Cold Formed Light Gauge Structural Steel Sections –
Overview
Status
Current
Usage level
Frequently Used
Domain
Structural Engineering — Structural Engineering and Structural Sections
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! IS 811 provides the geometric properties only; for the actual structural design and allowable stress calculations using these sections, engineers must use IS 801.
! Always verify the availability of specific profiles and thicknesses with local manufacturers, as fabricators often roll only a subset of the sections listed in the code.
! When detailing, remember that cold-formed sections have rounded corners; properties in the tables account for these standard inner bend radii.
North American Specification for the Design of Cold-Formed Steel Structural Members
Defines design rules for cold-formed steel members; IS 811 was historically based on an early version of this standard.
EN 1993-1-3:2006CEN (European Union)
MediumCurrent
Eurocode 3: Design of steel structures - Part 1-3: General rules - Supplementary rules for cold-formed members and sheeting
Provides design rules for cold-formed steel members and profiled sheets within the Eurocode framework.
AS/NZS 4600:2018Standards Australia / Standards New Zealand (Australia/New Zealand)
HighCurrent
Cold-formed steel structures
Specifies design requirements for cold-formed steel members, closely aligned with the North American AISI standard.
AISI Specification 1986 EditionAISI (US)
HighWithdrawn
Specification for the Design of Cold-Formed Steel Structural Members
Represents the contemporary international standard from the same era as IS 811:1987, sharing a very similar technical basis.
Key Differences
≠IS 811:1987 is based on the Allowable Stress Design (ASD) philosophy, whereas modern international standards like AISI S100 and EN 1993-1-3 are primarily based on Limit State Design (LSD) or Load and Resistance Factor Design (LRFD).
≠IS 811:1987 does not explicitly address the distortional buckling limit state, a critical failure mode for lipped sections common today. Modern codes like AISI S100 and AS/NZS 4600 have mandatory, detailed checks for distortional buckling.
≠The effective width formulas in IS 811 are simpler and based on older research. Modern standards use more refined formulas that better account for stress gradients, boundary conditions, and intermediate stiffeners.
≠Web crippling (bearing) provisions in IS 811 are based on a limited set of empirical formulas. International standards provide a much more extensive and accurate set of equations for various load cases, end conditions, and section geometries.
≠IS 811:1987 references older material standards (e.g., IS 1079). Current international codes incorporate a wider range of modern, high-strength steels and have more stringent requirements for material ductility.
Key Similarities
≈The fundamental concept of using an 'effective width' to account for the post-buckling reserve capacity of slender compression elements is a core principle shared by both IS 811 and all its international counterparts.
≈All standards classify cross-section elements as 'stiffened' or 'unstiffened' based on their edge support, which is a primary determinant in how local buckling is treated.
≈The general design approach for flexural members (beams) involves calculating section properties based on the effective cross-section (at a given stress level) and comparing demand to capacity.
≈All codes use interaction equations to check the adequacy of members subjected to combined axial load (compression) and bending, although the specific form of the equations and the factors used may differ.
Parameter Comparison
Parameter
IS Value
International
Source
Design Philosophy
Allowable Stress Design (ASD)
Limit State Design (LSD/LRFD) is primary; ASD is provided as an alternative method.
AISI S100-16
Factor of Safety (Bending)
1.67 (Allowable stress = 0.60 * Fy)
1.67 (ASD method safety factor Ωb)
AISI S100-16
Factor of Safety (Tension, on net section)
1.67 (Allowable stress = 0.60 * Fy)
1.67 (ASD method safety factor Ωt)
AISI S100-16
Modulus of Elasticity for Steel (E)
2.03 x 10^5 N/mm² (MPa)
203,000 MPa (29,500 ksi)
AISI S100-16
Check for Distortional Buckling
Not required / Not covered.
Mandatory check with specific design equations for calculating distortional buckling strength.
AS/NZS 4600:2018
Effective Width Formula (Stiffened Elements)
Based on a single formula: ρ = (C1/(λ)) * (1 - C2/(λ)), where λ is a slenderness term.
More complex formula: ρ = (1 - 0.22/λ_p) / λ_p, where λ_p is a plate slenderness parameter incorporating the buckling coefficient 'k'.
EN 1993-1-3
Maximum permissible flat-width-to-thickness ratio (w/t)
Does IS 811 provide design guidelines for cold-formed steel?+
No, IS 811 only provides dimensions, mass, and sectional properties. The design code for cold-formed steel is IS 801.
What types of sections are covered in this code?+
It covers angles, channels (with and without lips), hat sections, Z-sections (with and without lips), and tubular sections.
How are sections designated according to IS 811?+
They are designated by their basic shape prefix (e.g., C for Channel, LC for Lipped Channel), followed by web depth, flange width, and thickness in mm.