Australian Hollow Section Guide — RHS, SHS, CHS per AS 1163
Complete engineering reference for Australian structural hollow sections manufactured to AS 1163:2016. Covers Rectangular Hollow Sections (RHS), Square Hollow Sections (SHS), and Circular Hollow Sections (CHS) in Grades C350L0 and C450L0, including section properties, design considerations for compression, bending, and torsion, connection detailing, and worked examples per AS 4100:2020.
Related pages: AU Universal Beam Guide | AU PFC Channel Guide | Cold-Formed Steel Guide | HSS Connection Design
Hollow Section Nomenclature — AS 1163 Designation System
| Designation | Meaning | Example |
|---|---|---|
| RHS d x b x t | Rectangular Hollow Section: depth x width x thickness | RHS 200 x 100 x 6.0 |
| SHS d x t | Square Hollow Section: side length x thickness | SHS 100 x 100 x 5.0 |
| CHS d x t | Circular Hollow Section: outside diameter x thickness | CHS 168.3 x 5.4 |
The complete specification on a drawing should read: 'RHS 200 x 100 x 6.0 Grade C350L0 AS 1163'.
Square Hollow Section (SHS) Properties — Common Sizes
| Designation | Mass (kg/m) | d = b (mm) | t (mm) | A_g (mm^2) | I (10^6 mm^4) | Z (10^3 mm^3) | r (mm) |
|---|---|---|---|---|---|---|---|
| SHS 50 x 50 x 4.0 | 5.39 | 50 | 4.0 | 717 | 0.259 | 10.4 | 19.0 |
| SHS 65 x 65 x 4.0 | 7.28 | 65 | 4.0 | 969 | 0.603 | 18.6 | 25.0 |
| SHS 75 x 75 x 5.0 | 10.5 | 75 | 5.0 | 1390 | 1.16 | 30.9 | 28.9 |
| SHS 100 x 100 x 5.0 | 14.5 | 100 | 5.0 | 1890 | 2.87 | 57.4 | 39.0 |
| SHS 100 x 100 x 6.0 | 17.2 | 100 | 6.0 | 2240 | 3.33 | 66.6 | 38.6 |
| SHS 100 x 100 x 9.0 | 24.7 | 100 | 9.0 | 3190 | 4.52 | 90.4 | 37.6 |
| SHS 125 x 125 x 6.0 | 21.9 | 125 | 6.0 | 2840 | 6.71 | 107 | 48.6 |
| SHS 125 x 125 x 9.0 | 31.7 | 125 | 9.0 | 4120 | 9.23 | 148 | 47.3 |
| SHS 150 x 150 x 6.0 | 26.7 | 150 | 6.0 | 3440 | 12.0 | 160 | 59.0 |
| SHS 150 x 150 x 9.0 | 38.8 | 150 | 9.0 | 5030 | 16.7 | 223 | 57.7 |
| SHS 200 x 200 x 6.0 | 36.1 | 200 | 6.0 | 4640 | 29.1 | 291 | 79.1 |
| SHS 200 x 200 x 9.0 | 52.8 | 200 | 9.0 | 6830 | 41.2 | 412 | 77.7 |
| SHS 250 x 250 x 9.0 | 67.0 | 250 | 9.0 | 8630 | 82.6 | 661 | 97.9 |
| SHS 250 x 250 x 12.5 | 90.8 | 250 | 12.5 | 11700 | 108 | 864 | 96.0 |
Rectangular Hollow Section (RHS) Properties — Common Sizes
| Designation | Mass (kg/m) | d (mm) | b (mm) | t (mm) | Ix (10^6 mm^4) | Zx (10^3 mm^3) | rx (mm) | Iy (10^6 mm^4) | ry (mm) |
|---|---|---|---|---|---|---|---|---|---|
| RHS 100 x 50 x 5.0 | 10.5 | 100 | 50 | 5.0 | 1.18 | 23.6 | 34.8 | 0.38 | 19.7 |
| RHS 150 x 100 x 5.0 | 18.2 | 150 | 100 | 5.0 | 5.58 | 74.4 | 55.1 | 2.81 | 39.2 |
| RHS 150 x 100 x 6.0 | 21.5 | 150 | 100 | 6.0 | 6.45 | 86.0 | 54.5 | 3.23 | 38.6 |
| RHS 150 x 100 x 9.0 | 30.9 | 150 | 100 | 9.0 | 9.01 | 120 | 53.1 | 4.44 | 37.3 |
| RHS 200 x 100 x 5.0 | 22.1 | 200 | 100 | 5.0 | 11.5 | 115 | 74.5 | 3.67 | 41.6 |
| RHS 200 x 100 x 6.0 | 26.2 | 200 | 100 | 6.0 | 13.4 | 134 | 73.9 | 4.24 | 41.1 |
| RHS 200 x 100 x 9.0 | 37.9 | 200 | 100 | 9.0 | 18.9 | 189 | 72.0 | 5.87 | 39.8 |
| RHS 250 x 150 x 6.0 | 35.5 | 250 | 150 | 6.0 | 29.3 | 235 | 86.7 | 12.3 | 56.3 |
| RHS 250 x 150 x 9.0 | 52.0 | 250 | 150 | 9.0 | 42.0 | 336 | 84.9 | 17.4 | 54.8 |
Circular Hollow Section (CHS) Properties — Common Sizes
| Designation | Mass (kg/m) | OD (mm) | t (mm) | A_g (mm^2) | I (10^6 mm^4) | Z (10^3 mm^3) | r (mm) |
|---|---|---|---|---|---|---|---|
| CHS 48.3 x 4.0 | 4.37 | 48.3 | 4.0 | 557 | 0.135 | 5.59 | 15.6 |
| CHS 60.3 x 4.0 | 5.55 | 60.3 | 4.0 | 707 | 0.284 | 9.42 | 20.0 |
| CHS 76.1 x 4.0 | 7.11 | 76.1 | 4.0 | 906 | 0.594 | 15.6 | 25.6 |
| CHS 88.9 x 4.0 | 8.38 | 88.9 | 4.0 | 1070 | 0.967 | 21.8 | 30.1 |
| CHS 88.9 x 5.0 | 10.3 | 88.9 | 5.0 | 1320 | 1.16 | 26.0 | 29.7 |
| CHS 114.3 x 4.0 | 10.9 | 114.3 | 4.0 | 1390 | 2.09 | 36.6 | 38.9 |
| CHS 114.3 x 5.4 | 14.5 | 114.3 | 5.4 | 1850 | 2.70 | 47.3 | 38.3 |
| CHS 139.7 x 5.0 | 16.6 | 139.7 | 5.0 | 2120 | 4.84 | 69.3 | 47.8 |
| CHS 168.3 x 5.4 | 21.7 | 168.3 | 5.4 | 2760 | 9.23 | 110 | 57.8 |
| CHS 219.1 x 5.9 | 31.0 | 219.1 | 5.9 | 3950 | 22.6 | 206 | 75.7 |
AS 1163 Grade Properties — Complete Comparison
| Property | C250L0 | C350L0 | C450L0 |
|---|---|---|---|
| Yield strength fy (MPa) | 250 | 350 | 450 |
| Tensile strength fu (MPa) | 320 | 430 | 500 |
| Minimum elongation | 22% | 20% | 16% |
| Charpy V-notch (J at 0 degree C) | 27 min | 27 min | 27 min |
| Carbon equivalent max (CEV) | 0.40 | 0.43 | 0.45 |
| Design factor phi (flexure) | 0.90 | 0.90 | 0.90 |
| Design factor phi (compression) | 0.90 | 0.90 | 0.90 |
| AS 4100 buckling curve alpha_b | -0.5 | -0.5 | -0.5 |
| Relative cost (C350L0 = 1.0) | 0.85 | 1.00 | 1.12 |
Torsional Performance — Why Hollow Sections Excel
The key advantage of hollow sections over open sections is their superior torsional resistance:
| Section | Mass (kg/m) | J (10^3 mm^4) | Relative J |
|---|---|---|---|
| 200UB25.4 | 25.4 | 94 | 1.0 |
| SHS 100 x 100 x 6.0 | 17.2 | 5,340 | 56.8 |
| SHS 125 x 125 x 6.0 | 21.9 | 10,700 | 113.8 |
| CHS 114.3 x 5.4 | 14.5 | 5,400 | 57.4 |
Comparison: Hollow Sections vs Open Sections
| Design Criteria | Hollow Section (RHS/SHS/CHS) | Open Section (UB/UC/PFC) | Winner |
|---|---|---|---|
| Axial compression | Good (both axes balanced) | Good (UC), Poor (UB minor axis) | SHS/CHS |
| Major axis bending | Good | Better (more efficient flange) | UB |
| Torsion | Excellent | Very poor | RHS/CHS |
| Fire resistance (unprotected) | Better (lower section factor) | Worse (thinner elements) | SHS/RHS |
| Connection cost | Higher (special details) | Lower (standard bolting) | UB/UC |
| Corrosion resistance | Better (no crevices internally) | Worse (bolt holes trap water) | RHS/CHS |
| Aesthetics (architectural) | Excellent (clean lines) | Fair (industrial appearance) | SHS/CHS |
| Cost per tonne | 10-20% higher | Lower | UB/UC |
Worked Example: SHS Column Design
Problem: Design a square hollow section column for a 4.5 m effective length carrying a factored axial compression load N* = 580 kN. Use Grade C350L0 (fy = 350 MPa). Pinned ends in a braced frame.
Step 1: Determine effective length
ke = 1.00; Le = 4500 mm
Step 2: Trial section
Try SHS 125 x 125 x 6.0 Grade C350L0: A_g = 2840 mm^2, r = 48.6 mm
Step 3: Check form factor kf
Flat width b_f = 125 - 2 x 2.0 x 6.0 = 101 mm
lambda_e = (101/6.0) x sqrt(350/250) = 16.83 x 1.183 = 19.9
lambda_ey = 40 per AS 4100 Table 6.2.4. lambda_e = 19.9 < 40 — section is fully effective, kf = 1.0.
Step 4: Calculate modified slenderness
lambda_n = (4500/48.6) x 1.0 x sqrt(350/250) = 92.6 x 1.183 = 109.5
Step 5: Determine alpha_c (alpha_b = -0.5 for cold-formed hollow sections)
From AS 4100 Table 6.3.3(1): alpha_c = 0.575 (interpolated)
Step 6: Calculate member capacity
Ns = kf x An x fy = 1.0 x 2840 x 350 / 1000 = 994 kN
Nc = alpha_c x Ns = 0.575 x 994 = 572 kN
phi Nc = 0.90 x 572 = 514 kN < 580 kN — FAIL (utilisation = 1.13)
Step 7: Try heavier section
Try SHS 125 x 125 x 9.0: A_g = 4120 mm^2, r = 47.3 mm
lambda_n = (4500/47.3) x 1.0 x sqrt(350/250) = 95.1 x 1.183 = 112.5
alpha_c = 0.555
Ns = 1.0 x 4120 x 350 / 1000 = 1442 kN
Nc = 0.555 x 1442 = 800 kN
phi Nc = 0.90 x 800 = 720 kN > 580 kN — OK.
Result: SHS 125 x 125 x 9.0 Grade C350L0 AS 1163. Utilisation = 580/720 = 0.81.
Frequently Asked Questions
What is the difference between AS 1163 hollow sections and API 5L line pipe?
AS 1163 hollow sections are structural-grade products with guaranteed yield strength, tensile strength, elongation, and Charpy impact values. API 5L line pipe is manufactured for fluid transport and has different quality requirements. For structural applications in Australia, AS 1163 sections must be used unless the engineer explicitly accepts an alternative standard. AS 1163 sections come with a test certificate showing compliance with the structural standard.
Can hollow sections be galvanized after fabrication?
Yes, but hollow sections must have vent holes drilled at both ends (minimum 10 mm diameter for sections up to 100 mm, 12 mm for larger sections) to allow molten zinc to flow through and air to escape during the hot-dip galvanizing process. Without vent holes, trapped air will prevent zinc from coating the internal surface, and the expanding air may cause the section to rupture. The typical specification is two 12 mm diameter holes at each end.
How do I calculate the fire resistance of unprotected hollow sections?
The fire resistance depends on the section factor k_sm (exposed perimeter / volume of steel per unit length) in m^-1. For a fully exposed SHS 150 x 150 x 6.0, k_sm = approximately 174 m^-1. Hollow sections have lower k_sm values than open sections of equivalent mass, providing 5-15 minutes additional unprotected fire resistance. AS 4100 Clause 12 provides the full calculation method.
Are stainless steel hollow sections available to Australian standards?
Yes, stainless steel hollow sections are manufactured to AS/NZS 4673:2001. Common grades are 304 (austenitic) and 316 (marine grade). Stainless hollow sections cost approximately 4-6 times carbon steel per kg. They are typically stocked in limited sizes (50 x 50, 75 x 75, 100 x 100 SHS and 48.3, 60.3, 76.1 CHS). Larger sections require mill orders.
Educational reference only. All design values must be verified against the current edition of AS 4100:2020, AS 1163:2016, and the project specification. This information does not constitute professional engineering advice. Always consult a qualified structural engineer for design decisions.
Disclaimer: This content is for educational purposes only. Results must be verified by a licensed professional engineer. Steel Calculator provides preliminary design tools — NOT a substitute for professional engineering judgment.