# 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

$σ j ≤ f y γ m = f d$

## NPD

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.

$S d ≤ f k d = f k γ m ⋅ γ m k ( S d )$

Where:

• 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.