Canadian HSS Section Properties — Square, Rectangular, and Round per CSA G40.21

Complete reference for hollow structural section (HSS) properties per CSA G40.21 for Canadian structural steel design. Covers square HSS, rectangular HSS, and round HSS (CHS) with dimensions, mass, cross-sectional area, moment of inertia, section modulus, radius of gyration, plastic modulus, and torsional properties.

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CSA G40.21 HSS Designations

Canadian HSS follows CSA G40.21 with the designation:

HSS Depth × Width × Wall Thickness

Material: Typically CSA G40.21 Grade 350W (Fy = 350 MPa for t ≤ 20 mm) or 350WT for cold-weather applications.

HSS Classifications

HSS Type Shape Standard Sizes Typical Grade
Square HSS □ 51×51 to 305×305 mm 350W
Rectangular HSS ▭ 76×51 to 406×305 mm 350W
Round HSS (CHS) ○ 48.3 to 610 mm OD 350W

Square HSS — Section Properties (350W Typical)

Designation Mass kg/m A mm^2 Ix=Iy 10^6 mm^4 Sx=Sy 10^3 mm^3 rx=ry mm Zx=Zy 10^3 mm^3 J 10^3 mm^4
HSS 51×51×6.4 7.94 1010 0.38 14.7 19.4 18.5 5.5
HSS 76×76×6.4 12.6 1610 1.39 36.6 29.4 46.2 22.3
HSS 89×89×6.4 15.1 1930 2.33 52.3 34.8 66.4 37.8
HSS 102×102×6.4 17.5 2240 3.52 69.1 39.6 88.2 57.4
HSS 102×102×8.0 21.6 2750 4.22 82.8 39.2 107.0 67.4
HSS 127×127×6.4 22.3 2850 6.97 109.8 49.5 140.8 113.3
HSS 127×127×8.0 27.7 3530 8.45 133.1 49.0 172.8 134.5
HSS 127×127×10 34.1 4340 10.20 160.6 48.5 211.8 158.2
HSS 152×152×8.0 33.8 4300 14.8 194.7 58.7 256.8 326
HSS 152×152×9.5 39.7 5070 17.2 226.6 58.3 302.0 375
HSS 152×152×12.7 51.8 6610 21.8 287.2 57.5 392.6 466
HSS 178×178×8.0 40.1 5110 24.5 275.3 69.2 364.8 539
HSS 178×178×9.5 47.2 6030 28.6 321.1 68.9 430.4 623
HSS 178×178×12.7 62.0 7910 36.6 410.8 68.0 563.6 779
HSS 203×203×8.0 46.2 5890 37.0 364.2 79.3 485.6 811
HSS 203×203×9.5 54.5 6950 43.3 426.2 78.9 573.6 943
HSS 203×203×12.7 71.9 9160 55.7 548.6 78.0 752.0 1186
HSS 254×254×9.5 69.2 8830 87.4 688.2 99.5 931.2 1918
HSS 254×254×12.7 91.5 11670 113.4 893.0 98.9 1228 2476
HSS 305×305×9.5 84.0 10700 153.1 1005 119.6 1368 3372
HSS 305×305×12.7 111 14180 200.0 1311 118.8 1808 4370

Rectangular HSS — Selected Properties

Designation Mass kg/m A mm^2 Ix 10^6 mm^4 Sx 10^3 mm^3 Iy 10^6 mm^4 Sy 10^3 mm^3
HSS 152×76×8.0 25.4 3240 9.83 129 3.36 88.5
HSS 203×102×8.0 33.8 4300 22.8 225 7.72 151
HSS 203×152×8.0 40.1 5110 27.8 274 17.6 232
HSS 254×152×8.0 46.2 5890 52.0 410 23.2 306
HSS 254×152×9.5 54.5 6950 60.6 477 27.2 357
HSS 305×203×8.0 56.0 7140 100.1 657 52.1 513
HSS 305×203×9.5 66.2 8450 117.4 770 61.3 603
HSS 305×203×12.7 88.0 11220 152.8 1002 79.3 781
HSS 356×254×9.5 81.4 10390 209.3 1176 120.9 952
HSS 356×254×12.7 108 13830 275.0 1545 159.7 1258
HSS 406×305×9.5 96.5 12320 342.1 1685 214.7 1408
HSS 406×305×12.7 128 16380 451.5 2224 284.5 1866

Round HSS (CHS) — Selected Properties

Designation OD×t Mass kg/m A mm^2 I 10^6 mm^4 S 10^3 mm^3 r mm Z 10^3 mm^3
CHS 48.3×3.7 4.07 519 0.14 5.7 16.2 7.6
CHS 88.9×5.0 10.4 1320 1.20 27.1 30.2 36.0
CHS 114.3×5.0 13.5 1720 2.64 46.2 39.2 61.5
CHS 141.3×6.4 21.4 2730 6.40 90.5 48.4 119.4
CHS 168.3×6.4 25.7 3280 11.0 131 58.0 173
CHS 219.1×6.4 33.8 4310 24.4 223 75.3 295
CHS 273.1×7.9 52.0 6630 58.1 425 93.6 560
CHS 323.9×7.9 62.0 7910 98.2 606 111 800
CHS 355.6×7.9 68.2 8700 130.5 734 122 969
CHS 406.4×7.9 78.2 9980 196.0 965 140 1276

Design Values for HSS in Flexure

For HSS sections in bending per CSA S16 Clause 13.5:

Mr = phi × Z × Fy (Class 1 or 2)

For 350W steel: Mr (kN·m) = 0.90 × Z (10^3 mm^3) × 350 / 10^6 = 0.315 × Z

Moment Capacity — Common Square HSS

Section Zx (10^3 mm^3) Mr (kN·m) Used For
HSS 89×89×6.4 66.4 20.9 Light bracing, purlins
HSS 127×127×8.0 172.8 54.4 Medium bracing
HSS 152×152×9.5 302.0 95.1 Column/beam
HSS 203×203×9.5 573.6 180.7 Column, heavy brace
HSS 254×254×12.7 1228 386.8 Heavy column

Torsional Properties

HSS sections are excellent for torsional loading due to their closed cross-section:

Section J (10^3 mm^4) Cw (10^9 mm^6) Torsional Shear Stress at M=10 kN·m
HSS 89×89×6.4 37.8 0 17 MPa
HSS 127×127×8.0 134.5 0 12 MPa
HSS 152×152×9.5 375 0 10 MPa
HSS 203×203×9.5 943 0 8 MPa
HSS 254×254×12.7 2476 0 6 MPa

Closed HSS sections have Cw = 0 (no warping). Torsional resistance is purely St. Venant torsion (J).

Frequently Asked Questions

What is the radius of gyration of HSS 127×127×8.0? r = 49.0 mm for both axes (square HSS has equal rx and ry). This is used for column slenderness calculations: KL/r. For a 4.0 m HSS 127×127×8.0 column with K = 1.0: KL/r = 4000/49.0 = 81.6.

What is the plastic modulus Z of HSS 152×152×9.5? Zx = 302.0 × 10^3 mm^3. The plastic moment capacity in 350W steel: Mp = Zx × Fy = 302.0 × 350 / 1000 = 105.7 kN·m. Factored: Mr = phi × Mp = 0.90 × 105.7 = 95.1 kN·m.

What wall thickness is standard for HSS 203×203 HSS sections? Common wall thicknesses: 8.0 mm (46.2 kg/m), 9.5 mm (54.5 kg/m), 12.7 mm (71.9 kg/m). The 9.5 mm wall is the most common balance of strength and economy. Thicker walls increase compression capacity and improve section classification for seismic applications.

How do HSS sections perform in torsion? HSS sections are the most efficient structural shapes for torsional loading because of their closed cross-section. The St. Venant torsional constant J is much larger than for open sections (W-shapes). For example, HSS 203×203×9.5 has J = 943 × 10^3 mm^4, while a W310×39 has J = 370 × 10^3 mm^4 — despite the W-shape being heavier per metre.

Related Pages

This page is for educational reference. HSS properties per CSA G40.21-18. Verify section availability with steel suppliers and actual properties from CISC Handbook. Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent PE/SE verification.

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