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D12.A.2.6 Material Factor and Nominal Stresses

The design resistances are obtained by dividing the characteristic material strength by the material factor.

NS 3472

The material factor default value is 1.10. Other values may be input with the MF parameter. The nominal stresses should satisfy

σ j f y γ m = f d


The general requirement is according to NPD 3.1.1. For stability the NPD 3.1.1 and 3.1.3 requires that the structural coefficient is considered.

S d f k d = f k γ m γ m k ( S d )


  • Sd = reference stress or load effect resultant
  • fk = characteristic capacity
  • fkd = design capacity
  • γm = material coefficient
  • γmk = structural coefficient

γm is default set to 1.10.

γmk shall be equal to 1.0 for frames. For pipe members γmk is a function of the reduced slenderness. In the STAAD.Pro implemented NPD code this is calculated automatically.