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BS EN 1990/NA — Combinations of Actions

Eq.(6.10) against the (6.10a)/(6.10b) pair · seismic combination · serviceability combinations · governing case

⚠ Beta — verify the National Annex values

The EN 1990 combination expressions are well documented. γG, γQ, ξ and the ψ factors are Nationally Determined Parameters and have not been checked against the official UK National Annex.

ξ = 0.925 — the UK diverges from both EN and Germany

The UK NA is reported to use ξ = 0.925 in Eq.(6.10b), where the EN recommendation and the German position are both 0.85.
A higher ξ means less reduction of the permanent action, so the UK form of Eq.(6.10b) is more onerous. The difference is exactly Δξ · γG · G.
This matters for combinations only — it does not change a bending design, which is why a UK and a German bending calculation on the same section give identical reinforcement.
Confidence C: this value could not be confirmed against the official NA. Verify before use.

Characteristic actions

kN or kN/m

Nationally Determined Parameters and ψ factors

UK 0.925 · EN and DE 0.85

Ultimate limit state

CombinationClauseValueGoverns
Governing ULS value —

Serviceability limit state

CombinationClauseValue

References

§6.4.3.2 Eq.(6.10)γ_G·G + γ_Q,1·Q₁ + Σγ_Q,i·ψ₀,i·Q_i
Eq.(6.10a)γ_G·G + γ_Q,1·ψ₀,1·Q₁ + Σγ_Q,i·ψ₀,i·Q_i
Eq.(6.10b)ξ·γ_G·G + γ_Q,1·Q₁ + Σγ_Q,i·ψ₀,i·Q_i
UK NA to A1.3.1(4)ξ = 0.925 (reported UK value; EN recommendation 0.85)
§6.4.3.4 Eq.(6.12b)Seismic: G + ψ₂,1·Q₁ + A_Ed (no γ factors on G and Q)
§6.5.3SLS characteristic and quasi-permanent
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Engine: eurocode.js · GB-BSEN-UKNA.v1-beta ·

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Preliminary calculation tool. Final design requires the full official text of BS EN 1990 with its UK National Annex and review by a suitably qualified engineer.