Hollow Section (SHS / RHS / CHS)

Hollow steel sections are tubular structural members with rectangular (RHS), square (SHS), or circular (CHS) cross-section. Standardised in India by IS 4923:1997 (cold-formed) and IS 1161 (hot-finished). The major Indian manufacturers are TATA Hi-Steel (Tata Structura), Jindal Hollow, Surya Roshni, ESSAR Steel, Apollo Steel. Hollow sections are increasingly common in Indian construction for their architectural appeal (clean lines), torsional rigidity (closed section), and ease of corrosion protection (no internal corners to clean).

Design per IS 800:2007 covers hollow sections for tension, compression, bending, torsion, and combinations. The closed cross-section gives substantially higher torsional resistance than open sections (I, C, L) — a 100×100×4 SHS has 25× the torsional constant of a similar-size open angle. Compression behaviour is excellent — high radius of gyration with wall-thickness-to-width ratio limits per IS 800 Cl. 7.4 to prevent local buckling. Beam behaviour under flexure is governed by lateral-torsional buckling; the closed shape inherently resists LTB much better than open sections, making hollow beams attractive for laterally unsupported applications.

Indian applications: (1) PEB columns and primary members — RHS / SHS for clean architectural appearance; (2) Bracing and trusses in stadiums, atria — CHS gives unobstructed sightlines; (3) Lattice towers replacing angle members for higher strength-to-weight; (4) Architectural canopies, walkways, and railings; (5) Furniture and shop-fitting structural frames. Welding hollow sections requires specialised techniques because of internal access — often single-sided welds with full penetration through the wall thickness, requiring qualified welders and back-purging for inert-gas applications. The most common Indian fabrication issue is internal condensation in unfilled hollow sections — closed-end caps or vent holes are needed to prevent water accumulation in service.