Eurocode 3 Design Calculator

Eurocode 3 Structural Steel Design

Design structural steel members to EN 1993-1-1. The calculator classifies the section and checks section resistance, member buckling and lateral-torsional buckling for the entered design actions.

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.

Supported Section Types

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, M_y, and M_z action vector. Internal-part Class 3 limits use the resulting elastic plate-edge stress ratio ψ.
• If such a member is Class 4 and carries axial force with bending, or bending about both axes, effective properties for that combined loading are not calculated. The individual compression and bending checks are shown, but 6.2.9 and 6.3.3 are not made and are listed under Additional verification required; a gross-section bound check is shown that can only confirm a failure.
• Class 4 tee/angle bending is not checked because effective bending properties are unavailable, so the member reads PASS (partial) at best. Gross elastic moduli are used only in a bound check that can confirm a failure.
• No connection design (EN 1993-1-8), no fire design (EN 1993-1-2), and no fatigue checks (EN 1993-1-9).
• Slender I/channel web shear buckling needs confirmed transverse support stiffeners and an end-post detail at each end. Missing detail gives INCOMPLETE without a numerical shear-buckling capacity. EN 1993-1-5 local transverse force, patch loading, web bearing, end-post design, 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 compression includes torsional-flexural buckling (6.3.1.4): a coupled quadratic for equal angles and the lowest positive cubic root for unequal angles, using curve b. The thin-wall shear centre is at the leg mid-line intersection; enter effective lengths for the actual restraints. Ordinary angles with zero warping constant are insensitive to the torsional effective length.
• Channel, tee, and angle compression with bending: member stability interaction is not evaluated. Reported results cover the displayed section and component checks; verify combined member stability separately where required.
• Unequal-flange I-sections need an entered elastic critical moment Mcr for major-axis LTB, unless continuous top-flange restraint is set and the moment is sagging. Clause 6.3.3 compression-bending stability is not evaluated for this singly symmetric section, and other unavailable checks are identified in the results. Complete those checks separately.
• 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 the scope of this calculator.
• 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. Use the 3D FEA design check for torsion on closed hollow sections (RHS/SHS/CHS). Applied torsion on open sections requires separate warping verification.
• Only the CEN recommended values and the UK National Annex are built in. For other countries, select CEN recommended, enter that National Annex's γM factors and check its other nationally determined parameters.