This code covers the design criteria and construction guidelines for cold-formed light gauge steel structural members used in building construction. It is primarily based on the Working Stress Method (WSM) and is frequently used for designing roof purlins, side girts, and light-frame structures.
Specifies design and construction practices for cold-formed light gauge steel structural members in buildings.
Quick Reference Values
Basic permissible stress in tension and bending0.60 fy
Maximum flat-width ratio (unstiffened element)60
Maximum flat-width ratio (stiffened element)500
Maximum flat-width ratio (sub-stiffened element)60
Basic permissible shear stress0.40 fy
Key Formulas
b = (253 * t / sqrt(f)) * (1 - 50.3 / ((w/t) * sqrt(f))) — Effective width for stiffened compression elements
Fb = 0.60 * fy — Basic allowable design stress
Practical Notes
IS 801:1975 is based on the outdated Working Stress Method (WSM). Many modern structural engineers and PEB designers prefer using AISI S100 or Eurocode 3 Part 1-3 for Limit State Design of cold-formed steel.
Local buckling is the most critical design consideration. Ensure effective width calculations are performed accurately for thin compression elements.
For open unsymmetrical sections like C and Z purlins, torsional-flexural buckling must be carefully evaluated as they tend to twist under load.