According to EN 1993-1-3 [1], 3.2.2 (1), the average yield strength fya may be used in cases where the yield strength is indicated by the symbol fy if [1], 3.2.2 (4 ) to (8) applies.
The average yield strength fya can be determined by tests on the cold-formed steel cross-section or a simplified calculation method according to [1], Equation (3.1). The increased yield strength fya is calculated according to [1], Equation (3.1) as follows:
| Ag | Gross cross-section area |
| k | Deformation-dependent numerical value, k = 7 for roll profiling, k = 5 for other profiling methods |
| n | Number of deflections by 90° in the cross-section with an inner radius of r ≤ 5 ⋅ t (deflections below 90° are to be considered as fractions of n) |
| t | Design core thickness of the steel material before the cold forming, minus all metallic and organic coatings |
Example
The increased yield strength fya is determined for the sigma section shown in Figure 01 from S 355 EN 10025-2.
fyb = 35.5 kN/cm²
fu = 51.0 kN/cm²
Ag = 7.06 cm²
k = 7 for roll profiling
r = 2 mm ≤ 5 ⋅ 2.5 = 12.5 mm → all deflections may be applied
RF-STEEL Cold-Formed Sections
Cold-formed sections can be designed according to [1] and EN 1993-1-5 [2] with the RF-/STEEL Cold-Formed Sections module extension. The increased yield strength fya is considered in RF-/STEEL Cold-Formed Sections according to [1], Equation (3.1). It is assumed that the cross-section was created by roll profiling (for example, the deformation-dependent numerical value is applied with k = 7).
The increased yield strength fya is displayed in the result tables of RF-/STEEL Cold-Formed Sections. Image 02 shows the increased yield strength fya for the sigma section of this example.
2
Results
