Stability Check
Steel Column Slenderness Calculator
Use this page to see how unsupported length, weak-axis inertia, and area combine into the slenderness ratio that drives elastic column buckling.
Enter length in meters, E in GPa, inertia in cm^4, area in cm^2, and applied axial load in kN.
Buckling Inputs
End condition
Member data
Use the end condition that best matches the expected rotational restraint.
Use the weaker-axis inertia when buckling can occur about multiple axes.
Area is used to calculate the radius of gyration and slenderness.
Applied load is compared directly with the ideal Euler critical load.
Buckling Diagram
Stability Summary
| End condition | Pinned-Pinned |
| Effective length factor K | 1.000 |
| Radius of gyration r | 7.13 cm |
| Euler stress Fe | 597.97 MPa |
| Load margin Pcr - P | 1,789.17 kN |
Buckling Formula
Effective length
General form
L_e = K L
With current values
L_e = 1.000 * 4.20
Calculated result
L_e = 4.20 m
Euler critical load
General form
P_cr = pi^2 E I / L_e^2
With current values
P_cr = pi^2 * 210 * 1,710 / 4.20^2
Calculated result
P_cr = 2,009.17 kN
Slenderness ratio
General form
lambda = L_e / r, r = sqrt(I / A)
With current values
lambda = 4.20 / sqrt(1,710 / 34)
Calculated result
lambda = 58.87
This screen applies classical Euler elastic buckling and is most reliable for slender columns before inelastic or code-specific checks.
Model Assumptions
- The column is straight, prismatic, and loaded concentrically.
- Material behavior is linear elastic up to the predicted buckling load.
- Only ideal Euler global buckling is screened here; local buckling and imperfections are excluded.
Engineering Reading
Calculation Basis
Assumptions & Limits
- The model screens ideal global Euler buckling only and does not include local buckling or material nonlinearity.
- Imperfections, eccentricity, and frame sway effects need separate engineering review.
- K-factors are modeling assumptions about end restraint and should be treated as a sensitivity study when restraint is uncertain.
Reference Basis
- Documentation: Methodology
- Documentation: Engineering Review
- Roark's Formulas for Stress and Strain
- Mechanics of Materials references
- Euler buckling and column-stability references
Slenderness Reference Setup
| Member basis | Steel compression member under concentric axial load |
| Current end condition | Pinned-pinned |
| Current unsupported length | 4.2 m |
| Main driver | Effective length divided by radius of gyration |
| Use case | Early weak-axis stability check |
Engineering Notes
- This page is strongest when the design question is not the exact code resistance yet, but whether the member is drifting into a slender-column regime too early.
- Slenderness usually changes faster with unsupported length and weak-axis stiffness than with small shifts in steel grade, so geometry and restraint should be checked before material upgrades are assumed to solve the problem.
- If the column is part of a braced frame or has realistic partial rotational restraint, continue into the effective-length page and update the end condition assumptions before trusting the final ratio.
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