Flexural buckling
Determine the buckling curve, imperfection factor, and reduction factor χ about both principal axes to EN 1993-1-1 §6.3.1.
SKL-000056 · Skill
EN 1990EN 1993-1-1Design a steel column to Eurocode 3
Describe the column height, boundary conditions, section, steel grade, axial force, and end moments. Mia checks flexural buckling about both axes and the combined compression-bending interaction, then explains the governing result.
Mia guides you step by stepShe guides you through the inputs and explains the results.
Worked example
HEB 200 · 4.00 m · NEd 700 kN + MEd 40 kNm
Design verified: weak-axis buckling interaction governs- System
- Pinned–pinned column
- Section
- HEB 200 · S235
- Height
- 4.00 m
- Axial force
- NEd = 700 kN
- End moments
- M1 = M2 = 40 kNm (single curvature)
Design a braced HEB 200 steel column in S235, height 4.0 m, pinned at both ends, with NEd = 700 kN and equal end moments M1 = M2 = 40 kNm about the major axis (single curvature), the member restrained against lateral-torsional buckling, to EN 1993-1-1 (EN-recommended values). Check the cross-section resistance, flexural buckling about both axes, and the compression-bending interaction.
Key results
- Flexural buckling resistance Nb,z,Rd
- 1168 kN
- Bending resistance Mc,Rd
- 151.0 kNm
- Interaction, eq. 6.62
- η = 0.78
- Governing utilisation
- η = 0.78 (6.62, z-axis)
All values are deterministic for the stated inputs. EN-recommended partial factors (γM0 = γM1 = 1.00); buckling curve b about y-y and c about z-z (h/b = 1.0 ≤ 1.2); Annex B, Table B.1 interaction factors for a member not susceptible to torsional deformation.
- — χLT = 1.0: the member is confirmed restrained against lateral-torsional buckling.
- — Cross-section class 1 in both pure compression and bending; the c/t ratios are well inside the class-1 limits.
- — Equal end moments (ψ = 1, single curvature) give Cmy = 1.0.
Required inputs
- Column height and boundary conditions per axis
- Cross-section and steel grade
- Design axial force NEd
- End moments M1 and M2 (or zero for pure compression)
- Confirmation of lateral-torsional restraint and the National Annex
What you receive
- Governing check and utilisation
- Flexural buckling resistance about both principal axes
- Lateral-torsional buckling resistance when the column is not restrained
- Combined compression-bending interaction (EN 1993-1-1, 6.61/6.62)
- Assumptions and normative references
Reviewed calculation example
Start from an input template
These templates prefill the form with typical inputs. They are not calculated results; the calculation runs in CALC.
Prepare your calculation
Configure your column
System sketch
L = 4 mNEd = 700 kNM1 = 40 kNmM2 = 40 kNm
m
All required fields completed
All required fields completed
kN
kNm
kNm
All required fields completed
Yes
All required fields completed
Inputs completeReady to calculate
What this skill checks
Lateral-torsional buckling
For an unrestrained column, compute the elastic critical moment M_cr and the reduction factor χ_LT to EN 1993-1-1 §6.3.2 and fold it into the interaction check.
Combined compression and bending
Check the N+M interaction of §6.3.3 using the Annex B interaction factors, for both a restrained and an unrestrained member.
Cross-section resistance
Classify the section and verify the compression and bending resistance before the member stability checks.
Normative basis
Standards & references
The checks follow these standards. Nationally determined parameters come from the National Annex selected in the form.
EN 1993-1-1
WithdrawnEurocode 3: Design of steel structures – Part 1-1: General rules and rules for buildings
Edition used: DIN EN 1993-1-1:2010-12 (EN 1993-1-1:2005 + AC:2009) + DIN EN 1993-1-1/A1:2014-07
- §5.5
- §6.2
- §6.3.1
- §6.3.2
- §6.3.3
DIN MediaNewer edition: DIN EN 1993-1-1:2025-04 (EN 1993-1-1:2022)
| Country | National Annex | Factors | Source |
|---|---|---|---|
| DE | DIN EN 1993-1-1/NA:2022-10WithdrawnNewer edition: DIN EN 1993-1-1/NA:2026-04 | γM0 = 1.00γM1 = 1.10 | DIN Media |
| AT | ÖNORM B 1993-1-1:2017-11-01Current | γM0 = 1.00γM1 = 1.00 | Austrian Standards |
| CZ | ČSN EN 1993-1-1 ed. 2 (73 1401):2011-07 + A1 + Z1, NACurrentNewer edition: ČSN EN 1993-1-1 ed. 3 (73 1401) | γM0 = 1.00γM1 = 1.00 | shop.normy.biz |
| EN | Recommended valuesEN 1993-1-1:2005 + AC:2009 + A1:2014 | γM0 = 1.00γM1 = 1.00 | – |
Status checked on
EN 1990
CurrentEurocode: Basis of structural design
Edition used: DIN EN 1990:2021-10 (EN 1990:2002 + A1:2005 + A1:2005/AC:2010)
- §6.4.3.2
DIN MediaNewer edition: EN 1990:2023 (CEN; coexistence with the first generation until 2028-03-30)
| Country | National Annex | Factors | Source |
|---|---|---|---|
| DE | DIN EN 1990/NA:2010-12 + DIN EN 1990/NA/A1:2024-05Current | γG = 1.35γQ = 1.50 | DIN Media |
| EN | Recommended valuesEN 1990:2002 + A1:2005 + A1:2005/AC:2010 | γG = 1.35γQ = 1.50 | – |
Status checked on
Frequently asked questions
Frequently asked questions
InputsWhich inputs does Mia need for the design?
At minimum, the column height, boundary conditions, section, steel grade, axial force, and end moments (or zero for pure compression). Mia asks targeted questions when a governing input is missing.
VerificationDoes the check cover lateral-torsional buckling?
Yes. When the member is not restrained, Mia computes the elastic critical moment and the reduction factor χLT to EN 1993-1-1 §6.3.2 and includes it in the compression-bending interaction. A restrained member skips this calculation (χLT = 1.0).
VerificationWhich buckling curve is used?
Mia selects the curve from EN 1993-1-1 Table 6.2 based on the section's h/b ratio and flange thickness, and always states the curve it used.
Results & reportCan I document the calculation?
CALC presents inputs, assumptions, checks, the governing utilisation, and normative references in a structured answer that can be exported as a PDF.
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