What do the grades YST 210, YST 240, and YST 310 signify?

They signify the minimum yield stress of the steel tube in MPa. For example, YST 310 has a minimum yield stress of 310 MPa.

Does IS 1161 cover square and rectangular steel sections?

No, IS 1161 only covers circular steel tubes. IS 4923 covers square and rectangular hollow sections.

What is the acceptable tolerance on the thickness of welded structural tubes?

±10% for all sizes of welded tubes (Clause 9.1.2).

Is the weight of the tube calculated with or without galvanizing?

The nominal weights given in Table 3 are for black (un-galvanized) plain end tubes. If galvanized, an allowance for the zinc coating weight must be added.

IS 1161

: 2014

Steel Tubes for Structural Purposes - Specification

CurrentFrequently UsedSpecificationBIMStructural Engineering · Steel and Reinforcement

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This standard specifies the requirements for hot-finished and cold-formed circular steel tubes used for structural purposes. Structural engineers use this code to select the appropriate grade, dimensions, and mechanical properties for tubular elements in trusses, scaffolding, towers, and general building frames.

Specifies requirements for steel tubes suitable for structural purposes.

Quick Reference Values

Grades availableYST 210, YST 240, YST 310, YST 355

Tolerance on outside diameter (up to 48.3 mm)+0.4 mm, -0.8 mm

Tolerance on outside diameter (over 48.3 mm)±1.0%

Tolerance on thickness (welded tubes)±10%

Tolerance on thickness (seamless tubes)±12.5%

Tolerance on weight (single tube)+10%, -8%

Minimum yield stress for YST 310310 MPa

Practical Notes

A common mistake is specifying IS 1161 for Square or Rectangular Hollow Sections (SHS/RHS). IS 1161 applies strictly to circular tubes. For SHS/RHS, IS 4923 must be referenced.

Ensure the correct grade (e.g., YST 310) is clearly specified on drawings. The dimensions and nominal weights are identical across grades, but the load-carrying capacity varies significantly.

If tubes are to be used in corrosive environments, explicitly specify hot-dip galvanizing in accordance with IS 4736.