Question:
In the RF‑/STEEL EC3 add-on module, I obtain an extremely high design ratio for a member in the case of "Biaxial bending, shear and axial force". Although the axial force is relatively high, the design ratio seems unrealistic. Why?
Answer:
According to DIN EN 1993‑1‑1, Section 6.2.9, the moment resistance is reduced due to a high axial force utilization; thus, the maximum design ratio for the cross-section design "biaxial bending, shear and axial force according to 6.2.10 and 6.2.9" is unusually high.
By using Equation (6.2) from Section 6.2.1 for the cross-section design instead of Equation (6.41) from Section 6.2.9.1, the design ratio can be reduced significantly.
| NEd | Design value of the existing axial force |
| NRd | Design value of the allowable axial force |
| My,Ed | Design value of the existing bending moment about the local y-axis |
| My, Rd | Design value of the allowable bending moment about the local y-axis |
| Mz,Ed | Design value of the existing bending moment about the local z-axis |
| Mz, Rd | Design value of the allowable bending moment about the local z-axis |
In the RF‑/STEEL EC3 add-on module, you can activate the linear interaction of the axial force and moment loading in the Details tab; see the image.