Eurocode 3 Structural Steel Design
Design structural steel members according to EN 1993-1-1 standards. Our engine automates section classification and stability checks for any loading scenario.
Design Check Overview
EC3 categorizes sections into Classes 1–4 based on width-to-thickness ratios. This is critical for determining whether a section can reach its full plastic capacity or if local buckling will limit the design. Partial safety factors (γM0, γM1) provide resistance reduction margins, with values set by each country's National Annex.
Fabrication methods (rolled vs. welded) affect residual stresses, which in turn determine which EC3 buckling curve (a0, a, b, c, or d) is used for stability checks.
Clause Compliance Coverage:
- Section classification (5.5 / Table 5.2): I/H, channel, and RHS/SHS classes are evaluated from signed N, My, and Mz at every real force station. Internal-part Class 3 limits use psi from gross elastic plate-edge stresses; force-envelope maxima are not combined into a synthetic stress state.
- Class 4 effective sections (EN 1993-1-5): I/H, RHS/SHS, and supported channel component checks use pure-compression Aeff or pure-bending Weff. If the member is Class 4 and any real station has concurrent axial-flexural or biaxial demand, load-state-consistent effective properties are unavailable: 6.2.9 and 6.3.3 interaction rows are INCOMPLETE and suppressed while component rows remain. Tee/angle compression uses Aeff, but Class 4 tee/angle bending is INCOMPLETE; gross elastic section moduli are not substituted. CHS Class 4 shell resistance is OUT_OF_SCOPE.
- Section resistance (6.2.3-6.2.10): Tension, compression, bending, shear, shear-bending, and N+M section checks use the reported clause row.
- Member buckling (6.3.1 / 6.3.1.4): Flexural and supported torsional or flexural-torsional compression buckling checks are reported separately.
- LTB (6.3.2.1(3) / 6.3.2.2 / 6.3.2.3): LTB resistance uses the general or modified I/H reduction method according to the section family.
- Combined stability and torsion (6.3.3 / 6.2.6(4) / 6.2.7): Annex B stability interaction and closed-hollow-section torsion rows are reported where applicable.
Supported Section Types
I/H Sections - IPE, HEA, HEB, UKB, UKC
Channels - UPN, UAP, PFC
Tees - UBT, UCT
RHS / SHS
CHS
Angles - EA, UA
Current Limitations
- Tension rupture under 6.2.3 uses the entered Anet. Blank Anet defaults to gross area because bolt-hole paths are not inferred.
- Single member analysis only: no automatic frame buckling analysis or system-level effects.
- I/H, channel, and RHS/SHS classification uses the entered concurrent N, My, and Mz action vector. Internal-part Class 3 limits use the resulting elastic plate-edge stress ratio ψ.
- If one of those members is Class 4 and carries concurrent axial-flexural or biaxial demand, load-state-consistent effective properties are unavailable. Independent compression and bending component rows remain visible, but 6.2.9 and 6.3.3 are suppressed with an INCOMPLETE row rather than using gross or unrelated pure-action properties.
- Class 4 tee/angle bending is INCOMPLETE because effective bending properties are unavailable; gross elastic moduli are not substituted.
- No connection design (EN 1993-1-8), no fire design (EN 1993-1-2), and no fatigue checks (EN 1993-1-9).
- EN 1993-1-5 local transverse force, patch loading, web bearing, web buckling, end-post, and transverse-stiffener checks are not performed or derived from point loads, reactions, or connection forces. Check support bearing and concentrated load introduction regions separately.
- Angle sections: torsional-flexural buckling (6.3.1.4) not checked: doubly-asymmetric sections require a separate formulation not provided in EC3.
- CHS Class 4 is not designed: circular hollow sections beyond the EN 1993-1-1 Table 5.2 Class 3 limit require EN 1993-1-6 shell buckling, which is outside this member engine scope.
- The calculator assumes the default section orientation shown in the preview. Major and minor axis inputs are relative to that orientation. Rotated or sideways mono-symmetric members, such as channels, tees, and angles, should be checked in the FEA workflow.
- Torsion is not an input in the standalone calculator. In the FEA tool, closed hollow sections (RHS/SHS/CHS) use the 6.2.6(4) torsional shear stress check when a torsional section modulus is supplied or derivable; warping torsion for open sections is not performed.
- Partial safety factors (γM) must be verified against the relevant National Annex.
Benchmarks: 126 independent test cases, 0.43% average difference
Full Documentation →