Eurocode 3 Member Buckling Calculator

Axial compression + biaxial bending + shear according to EN 1993-1-1.
Member buckling checks about y-y and z-z using Eurocode interaction equations with simplified interaction factors to NCCI.

1. Inputs

Section

Steel grade (yield strength fy)

Select a section to see thickness-dependent fy reductions.

Buckling curve for y-y (major axis)

Buckling curve for z-z (minor axis)

Effective length L_cr,y (m, flexural buckling y-y)

Effective length L_cr,z (m, flexural buckling z-z and LTB)

Partial factors

γ_M0 = 1.0, γ_M1 = 1.0 (fixed in this tool, typical UK NA values).

Other assumptions

E = 210 000 MPa, LTB only for major-axis bending using same effective length as z-z compression, Class 4 sections not supported (effective widths are not implemented here).

Actions (design values)

Axial force N_Ed (kN, compression > 0)

Major-axis bending moment M_y,Ed (kNm)

Minor-axis bending moment M_z,Ed (kNm)

Major-axis shear force V_z,Ed (kN)

Typically associated with bending about y-y / major axis (web shear).

Minor-axis shear force V_y,Ed (kN)

Typically associated with bending about z-z / minor axis.

Governing η: —

2. Section diagram & properties

Stylised UC/UB I-section. Dimensions approximately to scale based on h, b, t_w, t_f.

3. Calculation steps & utilization

Sections are loaded from sections.json. Click “Calculate” to show detailed Eurocode 3 checks here.

Notes

Section classification is based on simplified EC3 slenderness limits for doubly-symmetric I sections in bending: flange outstand c/t and web depth d/t_w are checked. Governing class = max(flange class, web class).
Class 1/2: plastic behaviour using W_pl. Class 3: elastic behaviour using W_el. Class 4: effective widths not implemented – the tool will ask you to choose a more compact section.
Member buckling checks use Eurocode interaction equations (6.61, 6.62) with simplified interaction factors for doubly symmetric I sections.