StrucLab
| Project | — | Job No. | — |
| Calculation | P-Delta Stability — Inter-storey θ | By | — |
| Reference | AS 1170.4:2024 Cl 6.7.3 | Date | 23 May 2026 |
P-Delta Stability
AS 1170.4:2024 Cl 6.7.3 · Inter-storey stability coefficient θ · ETABS storey schedule
One row = one storey. P_tot = total gravity load above (ΣW, typically G + 0.3Q). V_s = seismic storey shear above (ΣF). Drift Δ per the "Drift input" mode above. h_si = inter-storey height (centre-to-centre). Units: kN, mm.
| Storey | P_tot (ΣW)kN | V_s (ΣF)kN | Drift Δmm | h_simm | θ | Amp | Verdict | ||
|---|---|---|---|---|---|---|---|---|---|
| 1 | 0.3429 | 1.370× | REDESIGN | ||||||
| 2 | 0.3429 | 1.370× | REDESIGN | ||||||
| 3 | 0.3429 | 1.370× | REDESIGN |
0Neglect (θ≤0.10)
0Amplify (0.10–0.20)
3Redesign (θ>0.20)
0.343Max θ — Storey 1
Stability coefficient per storey
θ = d_st·ΣW / (h_si·μ·ΣF). Drift input: elastic d_ie → d_st = d_ie·μ/Sp · μ = 2 · Sp = 0.77.
| Storey | P_tot (kN) | V_s (kN) | Δ in (mm) | d_st (mm) | h_si (mm) | θ | Amplifier | Verdict |
|---|---|---|---|---|---|---|---|---|
| Storey 1 | 115,000 | 5,600 | 45.0 | 116.9 | 3,500 | 0.3429 | 1.370× | REDESIGN |
| Storey 2 | 115,000 | 5,600 | 45.0 | 116.9 | 3,500 | 0.3429 | 1.370× | REDESIGN |
| Storey 3 | 115,000 | 5,600 | 45.0 | 116.9 | 3,500 | 0.3429 | 1.370× | REDESIGN |