Eurocode Steel Member Design (EN 1993-1-1)

## About this Eurocode Steel Member Design Calculator This calculation checks a rolled doubly symmetric I or H section (IPE, HEA, HEB) under axial force, shear and major-axis bending to Eurocode 3 (EN 1993-1-1). It runs cross-section classification, the section resistances, member buckling and the combined axial-plus-bending interaction, and reports a governing utilisation with a pass or fail. Every step is worked in visible maths. - **Structural steelwork engineers** pick a profile and grade, enter the design actions and read the governing check straight away. - **Design reviewers and checkers** trace each clause and intermediate value against EN 1993-1-1. - **Graduates and students** see how classification, buckling reduction factors and the interaction factors fit together. It is an engineering-grade calculation on CalcTree that you can duplicate, edit and fold into your own project workspace. ## More info on Eurocode Steel Member Design ### Inputs Choose the section profile and steel grade, set the member length and effective-length factor, and enter the design axial force, shear and major-axis moment. Section properties and yield and ultimate strengths are read from standard tables. ### Design checks Cross-section classification sets the applicable resistances. The calculation covers tension and compression, bending, shear, the bending-plus-shear and bending-plus-axial interactions, flexural buckling about both axes, lateral-torsional buckling, and the combined axial-plus-bending member interaction. ### Methods Resistances follow EN 1993-1-1, with buckling reduction factors from the relevant buckling curves and the member interaction from Annex B. The maths is carried in MathJS, with a single chart summarising the design-check utilisations. ## Common Calculation Errors to Avoid - **Wrong section class** assuming a plastic section when it is Class 3 or 4 overstates the bending and compression resistance. - **Missed lateral-torsional buckling** an unrestrained compression flange can buckle below the in-plane capacity. - **Wrong buckling axis or length** check both axes with the correct effective length. - **Axis confusion** keep major and minor axis moments and section properties consistent. - **Interaction skipped** the combined axial-plus-bending check must run when both act together.

## FAQs ### What does cross-section classification decide? Classification (Class 1 to 4) determines whether the section can reach its plastic moment, only its elastic moment, or is limited by local buckling. It sets which resistance formulae apply for bending and compression. ### When does lateral-torsional buckling govern? When the compression flange is not laterally restrained over the span, an unrestrained beam can buckle sideways below its in-plane bending capacity. The calculation reduces the bending resistance with the lateral-torsional buckling factor. ### How is combined axial force and bending handled? The member interaction from Annex B combines the axial and bending utilisations with interaction factors, checked about both axes. The governing utilisation is the largest across all checks. ### Which sections are supported? Rolled doubly symmetric I and H sections (IPE, HEA, HEB), selected from the built-in section library. ### Can I change the steel grade? Yes. The grade sets the yield and ultimate strengths, which flow through classification, the resistances and the buckling checks.