125x75x2.5RHS Rectangular Hollow Section
AS/NZS 1163Grade C450L0The 125x75x2.5RHS is a rectangular hollow section to AS/NZS 1163. It is 125 × 75 mm with a 2.5 mm wall, has a mass of 7.53 kg/m and a gross area of 959 mm². Its major-axis second moment of area is Ix = 2.07 × 10⁶ mm⁴ and in Grade C450L0 (fy = 450 MPa) its section moment capacity is φMsx = 14.1 kNm. Download its free DXF drawing (a true-scale CAD outline) below, or print the dimensioned drawing sheet.
Also written as: 125 x 75 x 2.5 RHS, 125x75x2.5 RHS
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Dimensions
| Symbol | Property | Value | Unit |
|---|---|---|---|
| d | Depth | 125 | mm |
| b | Width | 75 | mm |
| t | Wall thickness | 2.5 | mm |
| ro | External corner radius (used for properties) | 5.0 | mm |
Section properties
| Symbol | Property | Value | Unit |
|---|---|---|---|
| m | Mass per metre (nominal) | 7.53 | kg/m |
| Ag | Gross cross-section area | 959 | mm² |
| Ix | Second moment of area about x-axis | 2.07 | 10⁶ mm⁴ |
| Zx | Elastic section modulus, x-axis | 33.0 | 10³ mm³ |
| Sx | Plastic section modulus, x-axis | 40.0 | 10³ mm³ |
| rx | Radius of gyration, x-axis | 46.4 | mm |
| Iy | Second moment of area about y-axis | 0.942 | 10⁶ mm⁴ |
| Zy | Elastic section modulus, y-axis | 25.1 | 10³ mm³ |
| Sy | Plastic section modulus, y-axis | 28.2 | 10³ mm³ |
| ry | Radius of gyration, y-axis | 31.4 | mm |
| J | Torsion constant | 2053 | 10³ mm⁴ |
| C | Torsion modulus | 42.1 | 10³ mm³ |
| As | External surface area per metre | 0.391 | m²/m |
| As/t | External surface area per tonne | 52.0 | m²/t |
Axes: x-x is the major axis and y-y the minor axis, both through the centroid.
Design capacities to AS 4100
| Symbol | Property | Value | Unit |
|---|---|---|---|
| Steel grade | C450L0 (AS/NZS 1163) | ||
| fy | Yield stress used | 450 | MPa |
| fu | Tensile strength | 500 | MPa |
| kf | Form factor (Cl. 6.2.2) | 0.763 | |
| Section class, x-axis (Cl. 5.2) | Non-compact | ||
| Zex | Effective section modulus, x-axis | 34.7 | 10³ mm³ |
| φMsx | Section moment capacity, x-axis | 14.1 | kNm |
| Section class, y-axis | Slender | ||
| Zey | Effective section modulus, y-axis | 15.6 | 10³ mm³ |
| φMsy | Section moment capacity, y-axis | 6.3 | kNm |
| φNs | Section compression capacity (Cl. 6.2.1) | 296 | kN |
| φNt | Tension capacity, gross section (Cl. 7.2, kt=1, An=Ag) | 367 | kN |
| φVv | Shear capacity (Cl. 5.11) | 146 | kN |
| αb | Compression member section constant (Table 6.3.3) | -0.5 |
| Le (m) | φMbx (kNm) | φNcx (kN) | φNcy (kN) |
|---|---|---|---|
| 0.5 | 14.1 | 296 | 294 |
| 1 | 14.1 | 290 | 281 |
| 1.5 | 14.1 | 280 | 261 |
| 2 | 14.1 | 268 | 231 |
| 2.5 | 14.0 | 251 | 192 |
| 3 | 13.9 | 229 | 152 |
| 3.5 | 13.8 | 203 | 119 |
| 4 | 13.7 | 176 | 94.2 |
| 5 | 13.5 | 126 | 62.2 |
| 6 | 13.3 | 91.9 | 43.9 |
| 7 | 13.0 | 69.1 | 32.6 |
| 8 | 12.8 | 53.6 | 25.1 |
| 9 | 12.6 | 42.8 | 20.0 |
| 10 | 12.4 | 34.9 | 16.3 |
| 12 | 12.0 | 24.5 | 11.4 |
φMbx: AS 4100 Cl. 5.6.1.1 with αm = 1.0; Le = ktklkrL. φNc: Cl. 6.3.3, pin-ended effective length Le = keL, concentric load.
Check it for a span and loads with the beam calculator.
For restraint types, ktklkr and αm, use the lateral restraint calculator.
Instant check only. Effective lengths and moment modification factors must be determined by the designer in accordance with AS 4100 Cl. 4.6, 5.6.3 and 6.3.2. Not a substitute for a qualified engineer: see the disclaimer.
Alternatives with similar bending capacity
Sections from other families with a plastic modulus Sx within −8% / +25% of the 125x75x2.5RHS, lightest first.
| Section | Type | Mass (kg/m) | Sx (10³ mm³) | Ix (10⁶ mm⁴) |
|---|---|---|---|---|
| 100PFC | Parallel Flange Channel | 8.33 | 40.3 | 1.74 |
| 114.3x3.2CHS | Circular Hollow Section | 8.77 | 39.5 | 1.72 |
| 100x100x3.0SHS | Square Hollow Section | 8.96 | 41.2 | 1.77 |
| 101.6x4.0CHS | Circular Hollow Section | 9.63 | 38.1 | 1.46 |
| 114.3x3.6CHS | Circular Hollow Section | 9.83 | 44.1 | 1.92 |
| 101.6x5.0CHS | Circular Hollow Section | 11.9 | 46.7 | 1.77 |
Other rectangular hollow sections
Relevant Australian Standards
- AS/NZS 1163:2016 Cold-formed structural steel hollow sections
Covers cold-formed CHS, RHS and SHS in Grades C250L0, C350L0 and C450L0, including the corner-radius and thickness tolerances used to calculate section properties. - AS 4100:2020 Steel structures
The Australian design Standard for steel members and connections. Covers section classification (Section 5), member moment capacity including lateral-torsional buckling (5.6), shear (5.11), axial compression (Section 6), tension (Section 7) and combined actions (Section 8). - AS/NZS 1554.1:2014 Structural steel welding – Welding of steel structures
Weld procedures, welder qualification, weld categories (SP and GP) and inspection requirements for structural welds. - AS/NZS 2312.1:2014 & 2312.2:2014 Guide to the protection of structural steel against atmospheric corrosion
Part 1 covers protective paint coatings and Part 2 hot-dip galvanizing; both use the external surface areas given on each section page.
See all Australian Standards for structural steel.
Properties are calculated from nominal dimensions, including root and toe radii, as described in notation & method. Mass is the nominal catalogue mass; the calculated mass at 7850 kg/m³ is 7.53 kg/m. Verify against current manufacturer literature before use in design. Spotted an error? Report it.