Steel · Members & beams
Steel beam (UB) calculator
Section and member moment capacity (lateral-torsional buckling), shear and deflection, with built-in UB sizes.
Standard: AS 4100 Cl 5.1–5.6, 5.11 · AS/NZS 1170.0
Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| Section | 310UB40.4 | |
| Span (simply supported) | 6 | m |
| Segment length between restraints | 2 | m |
| Effective length factor | 1 | |
| Moment modification αm | 1.13 | |
| Dead load (excl. self-wt) | 6 | kN/m |
| Live load | 8 | kN/m |
| Point load at midspan (live) | 0 | kN |
| Deflection limit L/ | 250 |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Self-weight | 0.39 | kN/m |
| Compact section? | Yes | |
| Ze | 617 | ×10³ mm³ |
| φMs (section) | 178 | kNm |
| Mo (elastic buckling) | 591 | kNm |
| αs | 0.858 | |
| φMb (member) | 172 | kNm |
| M* | 88.5 | kNm |
| φVv | 320 | kN |
| V* | 59.0 | kN |
| Deflection (G + 0.7Q) | 12.0 | mm |
| Limit | 24.0 | mm |
- ✓ Bending M* ≤ φMb — utilisation 51%
- ✓ Shear V* ≤ φVv
- ✓ Deflection ≤ L/250
Method, formulas and assumptions
- Properties from plate dimensions (root radii ignored): Ix = 84.3×10⁶, Sx = 617×10³ mm³, Iy = 7.64×10⁶ mm⁴
- Flange λe = (b − tw)/(2tf)√(fy/250) = 8.8 (compact ≤ 9); web λe = 52.6 (≤ 82)
- Ms = fy Ze, φ = 0.9; Mo = √[(π²EIy/Le²)(GJ + π²EIw/Le²)]
- αs = 0.6[√((Ms/Mo)² + 3) − Ms/Mo]; Mb = αm αs Ms ≤ Ms
- Vv = 0.6 fy d tw (stocky web); δ = 5wL⁴/384EI + PL³/48EI
- Check section values against current manufacturer tables before use.
Related steel calculators
- Steel angle lintel — Equal-angle lintel over a masonry opening with triangular (arching) or full masonry load.
- Steel I-beam in torsion with warping — UB or UC simply supported with fork ends (twist prevented, warping free) carrying an eccentric point load at…
- Tension member: net area & stagger — Gross yield and net-section fracture with staggered holes (s²t/4g) and the correction factor kt for…
- Beam lateral–torsional buckling (restraint options) — Segment capacity with restraint arrangement, load height and rotational restraint factors and αm options…
- Web bearing: yield & buckling — Unstiffened web bearing yield (1.25 bbf tw fy) and bearing buckling with αc at le/r = 2.5 d1/tw for library…
- Welded plate girder (flexure & shear) — Section properties from plates, effective section modulus with flange/web slenderness, web shear buckling…
- Castellated beam (net tee checks) — Parent I-section expanded by the cut depth: global bending carried as tee axial forces, Vierendeel bending…
- Composite steel–concrete beam — Effective width, plastic neutral axis in the slab, positive moment capacity and stud count for full shear…
- Stair stringer — Inclined stringer carrying half the stair: horizontal-span moment, shear, and deflection along the incline.
- SHS / RHS beam: bending & shear — Section modulus and compactness of a rectangular hollow section in major-axis bending, web shear capacity…
For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.