Structural sections
A 310 UB 40.4 is 304.0 mm deep and weighs 40.4 kg/m, so a 6 m length is 242.4 kg. Choose a universal beam or column, a parallel flange channel, an angle, or a square, rectangular or circular hollow section for its dimensions, its section properties as the makers publish them, and the mass of the length you cut.
The section is drawn to scale from its dimensions, with its centroid and the axes its properties are about: an angle’s principal axes tilt to its legs, and a channel’s shear centre sits off the back of its web.
- Mass of 6000 mm
- Mass per metre
- Area Ag
- Ix
- Zx
- Sx
- rx
- Iy
- Zy
- Sy
- ry
- J
- Iw
How it’s calculated
Mass of a cut length = mass per metre × length ÷ 1000. Z = I ÷ the distance to the farthest fibre; r = √(I ÷ Ag).
| Designation | Mass kg/m | d mm | bf mm | tf mm | tw mm | r1 mm | Ag mm² | Ix ×10⁶ mm⁴ | Zx ×10³ mm³ | Sx ×10³ mm³ | Iy ×10⁶ mm⁴ | Zy ×10³ mm³ | J ×10³ mm⁴ |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 360 UB 50.7 | 50.7 | 355.6 | 171.0 | 11.5 | 7.3 | 11.4 | 6470 | 142 | 798 | 897 | 9.60 | 112 | 241 |
| 360 UB 44.7 | 44.7 | 352.0 | 171.0 | 9.7 | 6.9 | 11.4 | 5720 | 121 | 689 | 777 | 8.10 | 94.7 | 161 |
| 310 UB 46.2 | 46.2 | 307.2 | 166.0 | 11.8 | 6.7 | 11.4 | 5930 | 100 | 654 | 729 | 9.01 | 109 | 233 |
| 310 UB 40.4 | 40.4 | 304.0 | 165.0 | 10.2 | 6.1 | 11.4 | 5210 | 86.4 | 569 | 633 | 7.65 | 92.7 | 157 |
| 310 UB 32.0 | 32.0 | 298.0 | 149.0 | 8.0 | 5.5 | 13.0 | 4080 | 63.2 | 424 | 475 | 4.42 | 59.3 | 86.5 |
| 250 UB 37.3 | 37.3 | 256.2 | 146.0 | 10.9 | 6.4 | 8.9 | 4750 | 55.7 | 435 | 486 | 5.66 | 77.5 | 158 |
| 250 UB 31.4 | 31.4 | 251.6 | 146.0 | 8.6 | 6.1 | 8.9 | 4010 | 44.5 | 354 | 397 | 4.47 | 61.2 | 89.3 |
What do I, Z, S and r tell you about a section?
I, the second moment of area, is the section’s stiffness in bending: deflection goes as 1/I. Z, the elastic modulus, is I over the distance to the farthest fibre; a bending moment M stresses that fibre to M/Z. S, the plastic modulus, is the same for the section fully yielded, and is larger than Z. r, the radius of gyration, √(I/A), is what a column’s slenderness is measured with.
Hot-rolled sections are to AS/NZS 3679.1 and hollow sections to AS/NZS 1163; the values are the makers’ catalogue values, each cross-checked against a second catalogue and against the outline drawn here.