HSS Section Properties Quick Reference — Square, Rectangular & Round

Comprehensive quick-reference tables for Hollow Structural Section (HSS) properties per AISC 360. Covers square HSS, rectangular HSS, and round HSS sections with cross-sectional area (A), moment of inertia (Ix), elastic section modulus (Sx), radius of gyration (rx), plastic section modulus (Zx), and torsional constant (J). All values from the AISC Steel Construction Manual, 16th Edition.

HSS sections are cold-formed per ASTM A500 and are the preferred choice for columns, braces, truss chords, and any application requiring torsional resistance or biaxial bending capacity. Their closed cross-section gives them vastly superior torsional stiffness compared to open sections like W-shapes.

Understanding HSS Properties

PRELIMINARY — NOT FOR CONSTRUCTION. All results are for educational and reference use only. Must be independently verified by a licensed Professional Engineer (PE) or Structural Engineer (SE) before use in any project.

Square HSS — Section Properties

Square HSS sections are designated by nominal outside dimensions and wall thickness (e.g., HSS6x6x3/8 is 6 in x 6 in square with 3/8 in wall). Properties are identical in both axes (Ix = Iy, Sx = Sy, rx = ry).

Rectangular HSS — Section Properties

Rectangular HSS sections have different properties in each axis (Ix for strong axis about the longer dimension, Iy for weak axis about the shorter dimension). They are designated as HSS B x D x t where B = width, D = depth.

Round HSS — Section Properties

Round HSS sections are designated by nominal outside diameter and wall thickness (e.g., HSS6.625x0.250 is 6-5/8 in OD with 1/4 in wall). Properties are identical in all directions, making round HSS ideal for multi-directional loading, flagpoles, and sign supports.

Source: AISC Steel Construction Manual, 16th Edition, Tables 1-10 through 1-12. All values for ASTM A500 Gr B/C cold-formed HSS.

Column Design with HSS

Square HSS sections excel at column design because rx = ry. For a given axial demand (Pu) and effective length (KL), the selection process is:

1. Calculate required r: r*req = KL / lambda_target. For Fy = 46 ksi (Gr B), the inelastic-to-elastic transition occurs at lambda = 4.71 * sqrt(E/Fy) = 4.71 _ sqrt(29000/46) = 118. Conservative design targets lambda = 60-80.
2. Scan the rx column for sections meeting r_req.
3. Check wall slenderness: b/t limits for compact sections = 1.12 * sqrt(E/Fy). For 46 ksi: b/t limit = 28.1. For an HSS6x6x1/4 with 6 in nominal and 0.233 design wall: b/t = (6 - 3*0.233)/0.233 = 22.8, which is less than 28.1, so the section is compact.
4. Calculate phi_Pn: phi*Pn = 0.90 * A _ Fcr, where Fcr is determined per AISC 360 Chapter E3.

Key design note: HSS wall thickness is measured as nominal thickness, but AISC requires using a design wall thickness of 0.93 * t_nominal. This 7% reduction accounts for manufacturing tolerance.

Torsional Comparison: HSS vs W-Shapes

The table below illustrates why HSS is the clear choice for torsion-critical members. J values for HSS are 30-100 times larger than comparable W-shapes.

This torsional advantage makes HSS the default choice for curved beams, canopy frames, sign structures, and any member subject to eccentric loading that produces significant torsion.

Frequently Asked Questions

What is the difference between square, rectangular, and round HSS? Square HSS (equal rx = ry) is best for columns and concentric braces where loading direction is uncertain. Rectangular HSS is best for beams where depth is more important than width, providing higher Ix at the expense of Iy. Round HSS has the highest torsional efficiency (J per unit weight) and is preferred for poles, piles, and architectural applications requiring a smooth circular profile.

What does design wall thickness (0.93t) mean? Per AISC 360 Section B3.12 and AISC Specification Table B4.1a, the design wall thickness for HSS is 0.93 times the nominal wall thickness. This reduction accounts for the manufacturing tolerance of +/-10% on wall thickness that is permitted by ASTM A500. All section properties in the AISC Manual and in this table are calculated using the design wall thickness (0.93t), not the nominal thickness.

How do I calculate the weight of an HSS member? Weight per foot = A _ 3.40 lb/ft per in^2 of steel. Example: HSS6x6x3/8 has A = 8.01 in^2, so weight = 8.01 _ 3.40 = 27.2 lb/ft, which matches the manual value of 27.2 lb/ft. For metric: weight (kg/m) = A (mm^2) * 7,850 / 1,000,000.

Are HSS sections more expensive than W-shapes? On a per-pound basis, HSS typically costs 15-30% more than W-shapes. However, for column applications the weight savings from using HSS (with rx = ry, no weak axis) often offset the material cost premium. Total installed cost comparison should account for connection complexity — HSS connections often require slotting, through-plates, or end plates that add fabrication cost.

Where can I find HSS connection design information? Refer to AISC Design Guide 24: Hollow Structural Section Connections. For bolted connections, through-bolts with bearing checks on the HSS wall are common. For welded connections, AWS D1.1 provides prequalified joint details. Our HSS Connection Design Guide covers common connection types.

Try it now: Select an HSS section with our free column calculator

Related Pages

• Section Properties Lookup — Full database of W, HSS, UB, IPE sections
• HSS Connection Design Guide — Bolted and welded HSS connections
• HSS Weight Calculator — Weight per foot and total weight
• Column Buckling Calculator — Uses rx and ry for HSS and W-shape columns
• Steel Truss Design — HSS as truss chords and web members

Disclaimer

This page is for educational and reference use only. It does not constitute professional engineering advice. All design values must be verified against the applicable standard and project specification before use. The site operator disclaims liability for any loss arising from this information.

Design Resources

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• Column Capacity Calculator
• Beam Capacity Calculator
• Steel Weight Calculator

Design guides

• HSS Connection Design — AISC DG24
• Torsion Design Guide
• Brace Connection Design