Table 1 — Square HSS (AISC, ASTM A500 Grade C, Fy = 50 ksi)

Common sizes ordered by outer dimension. Ix = Iy and Sx = Sy for square sections.

Notes: Fy = 50 ksi for ASTM A500 Grade C (round sections: 46 ksi). A1085 specifies Fy = 50 ksi, Fu = 65 ksi for all shapes with tighter tolerances. b/t = (B − 3t_des)/t_des per AISC 360.

Table 2 — Rectangular HSS (AISC, ASTM A500 Grade C)

Selected sizes covering the most common H×B combinations. Ix ≠ Iy; Ix is about the strong axis (H direction).

Table 3 — Round HSS / Circular Hollow Sections (AISC, ASTM A500 Grade C, Fy = 46 ksi)

Round HSS is designated by outer diameter × wall thickness (both in inches). I = J/2 for round sections.

Australian SHS/RHS/CHS (AS/NZS 1163, Grade C350L0 — fy = 350 MPa, fu = 430 MPa)

Square Hollow Sections (SHS) — selected sizes

Rectangular Hollow Sections (RHS) — selected sizes

Steel Grades for HSS

A1085 vs A500: ASTM A1085 was introduced in 2014 to address common criticisms of A500 — large dimensional tolerances, corner radius variations, and occasional very low Fy/Fu ratios. A1085 requires:

• Minimum Fy/Fu ≥ 0.85 (capped Fy/Fu for ductility)
• Maximum Fy ≤ 70 ksi (prevents over-yielding in seismic)
• Charpy V-notch impact testing at −20°F
• Tighter dimensional tolerances than A500

A1085 is the preferred grade for seismic applications and is specified by AISC 341 for special moment frames and special concentrically braced frames.

Key Design Properties

Local Buckling (b/t and D/t Limits)

AISC 360 classifies HSS walls as compact, noncompact, or slender based on width-to-thickness ratios:

Square/rectangular HSS walls:

Round HSS (D/t):

Compact sections can develop the full plastic moment Mp = Fy × Z. Noncompact and slender sections require reduced moment capacity per AISC 360 Chapter F Table F7 (rectangular) and Table F8 (round).

Torsional Properties

HSS sections are efficient in torsion because their closed cross-section gives a high torsional constant J:

• Square/rectangular HSS: J ≈ 2t × (b−t)²(h−t)² / (b−t + h−t) (thin-wall approximation)
• Round HSS: J = π(D⁴ − Di⁴)/32 (exact, same as I for round sections)

For round HSS, J = 2I exactly. This makes CHS the most efficient profile for torsion-dominant loads (canopy edge beams, curved members, bridge diaphragms).

Slenderness Ratio for Columns (KL/r)

Use rx = ry from the table above. For square HSS, both axes are equal. For rectangular HSS, ry governs (minor axis). Maximum KL/r = 200 per AISC 360.

Frequently Asked Questions

What is the most common HSS size? HSS 8×8×3/8 and HSS 6×6×1/4 are among the most widely stocked square HSS sizes. For rectangular HSS, 8×4 and 10×6 are common structural frame choices. Availability varies by region and supplier; always confirm stocking with your fabricator.

What is the difference between HSS and pipe? Structural pipe (ASTM A53 Grade B) is specified by nominal pipe size (NPS) and schedule, with wall thickness defined by schedule number. HSS round sections are specified by OD × wall thickness with ASTM A500/A1085 material properties. Pipe and round HSS have similar shapes but different dimensional standards, material properties, and code applicability. AISC 360 permits both; AS 4100 uses CHS per AS/NZS 1163.

Does ASTM A500 have a higher Fy than A36? Yes. ASTM A500 Grade C has Fy = 50 ksi vs 36 ksi for A36. However, A36 is not typically produced as HSS — A500 and A1085 are the standard HSS materials.

Can I use HSS in seismic moment frames? Yes, with specific requirements. AISC 341 (Seismic Provisions) permits HSS columns in special moment frames (SMF) if they are compact, A1085 or A500 Grade C is specified, and b/t limits are met. Connections to square/rectangular HSS columns require special detailing to develop beam plastic hinges at the connection face.

What is the weight of HSS per foot? See the tables above. As a quick rule: weight (lb/ft) ≈ 3.40 × A (in²) for A500 HSS. For example, HSS 6×6×3/8 with A = 8.08 in²: 3.40 × 8.08 ≈ 27.5 lb/ft (actual: 27.7 lb/ft).

What is the axial compression capacity of an HSS 8×8×3/8 column at 15 ft height? For HSS 8×8×3/8 (A500 Grade C, Fy = 50 ksi): A = 11.1 in², rx = ry = 3.21 in. With pinned-pinned conditions (K = 1.0) and L = 15 ft = 180 in: KL/r = 180/3.21 = 56.1. Fe = π²E/(KL/r)² = π² × 29,000/56.1² = 91.1 ksi. Since KL/r < 4.71√(E/Fy) = 113, inelastic buckling governs: Fcr = 0.658^(Fy/Fe) × Fy = 0.658^(50/91.1) × 50 = 40.3 ksi. φPn = 0.90 × 40.3 × 11.1 = 402 kips. This is the AISC 360 Chapter E result for a typical braced column.

How do you check local buckling for an HSS column? For square/rectangular HSS, the wall b/t ratio must be compared to the compact limit of 2.26√(E/Fy). For A500 Grade C (Fy = 50 ksi): compact limit = 2.26√(29,000/50) = 54.4. Wait — AISC uses b/t = (B − 3t)/t for HSS walls. For HSS 8×8×3/8 (t_des = 0.349 in): b/t = (8 − 3×0.349)/0.349 = (8 − 1.047)/0.349 = 19.9. This is well below 26.9 (compact limit for Fy = 50 ksi using the column slenderness criterion of 1.40√(E/Fy)), so the section is compact for compression and the full column buckling capacity applies.

Run This Calculation

→ Beam Capacity Calculator — bending, shear, and LTB capacity for HSS beams per AISC 360, AS 4100, EN 1993, or CSA S16.

→ Column Capacity Calculator — axial compression capacity for square, rectangular, or round HSS columns with KL/r checks.

→ Section Properties Calculator — look up Ix, Sx, Zx, rx, ry, and torsional properties for any HSS designation.

Try it now: Check your section properties with our free Moment of Inertia calculator →

Related pages

• HSS Connection Design Calculator — weld and bolted HSS connections per AISC 360 Chapter K
• Beam Capacity Calculator — bending and shear capacity for HSS and W-sections
• Column Capacity Calculator — axial compression capacity for HSS columns
• Steel Weight Calculator — weight of HSS cut lists by length
• Concrete-Filled HSS Reference — CCFT/RCFT composite column design
• Steel Section Types Guide — comparison of all structural steel shape families
• Steel Grades Reference — ASTM A500, A1085, AS/NZS 1163, EN 10210 material properties
• Wide Flange Beam Sizes — W-shape properties for comparison with HSS sections
• HSS Connection Design
• structural steel weight per foot table
• Steel Pipe Schedule Chart

Educational reference only. Always verify HSS dimensions and properties against the current AISC Steel Construction Manual, AS/NZS 1163, or EN 10210/10219 as applicable to your project.

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