Analysis & loading · Load take-down & combinations
Gravity load take-down calculator
Column axial load storey by storey with dead, live, live-load area reduction and ULS/SLS combinations.
Standard: AS/NZS 1170.0 combinations · AS/NZS 1170.1 Cl 3.4.2 area reduction
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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 |
|---|---|---|
| Number of levels (roof included) | 6 | |
| Tributary area per floor | 30 | m² |
| Floor dead load (incl. slab) | 6.5 | kPa |
| Floor live load | 3 | kPa |
| Roof dead load | 1.5 | kPa |
| Roof live load | 0.25 | kPa |
| Column self-weight per storey | 12 | kN |
| Apply area reduction ψa | Yes |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Below roof: G, Q, ψa | 57, 8, 1.00 | N* = 80 kN · Ns = 62 |
| Below level 5: G, Q, ψa | 264, 98, 0.85 | N* = 442 kN · Ns = 323 |
| Below level 4: G, Q, ψa | 471, 188, 0.69 | N* = 762 kN · Ns = 563 |
| Below level 3: G, Q, ψa | 678, 278, 0.62 | N* = 1,074 kN · Ns = 800 |
| Below level 2: G, Q, ψa | 885, 368, 0.57 | N* = 1,383 kN · Ns = 1,035 |
| Below level 1: G, Q, ψa | 1,092, 458, 0.54 | N* = 1,689 kN · Ns = 1,269 |
- ✓ 1.2G + 1.5Q governs over 1.35G
Method, formulas and assumptions
- G and Q summed from the roof down, with column self-weight
- ψa = 0.3 + 3/√A ≥ 0.5 applied to floor live load (A = cumulative floor area supported; not for storage/assembly)
- ULS N* = max(1.2G + 1.5ψaQ, 1.35G); SLS Ns = G + 0.7ψaQ
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.