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} \leq \frac{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} \leq f_{k d} = \frac{f_{k}}{γ_{m} \cdot γ_{m k} (S_{d})}

Where:

S_d = reference stress or load effect resultant
f_k = characteristic capacity
f_kd = design capacity
γ_m = material coefficient
γ_mk = structural coefficient

γ_m is default set to 1.10.

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