Material properties, shared by every verification. The cross-section is not shared: SIA 263 classifies it from the internal forces, so it belongs to each verification and appears with it.
Checks any steel section entered by its properties under a moment and an axial force in compression or tension, to SIA 263:2013: the section resistance, flexural buckling about both axes and the interaction of bending and compression. Every step shows its formula and the clause it comes from.
You enter fy,k from table 1 of your copy of SIA 263, for the grade and the plate thickness, E (clause 2.2), the section class under these forces (table 4), the area A, the radii of gyration iy and iz, the plastic section modulus Wy,pl, the buckling curve a, b, c or d for each axis, and γM1 (clause 4.1.3). Then the sense and magnitude of NEd, the largest moment My,Ed, the moment diagram with Mmin and the signs of the end moments, and bending about the strong axis only or about both axes. For the member: the buckling lengths, entered or derived from the length l, the end conditions and the intermediate supports ny and nz in each plane. For lateral-torsional buckling: prevented, or the critical moment McrD entered.
You get the resistances, the slendernesses, the buckling resistances and the utilisation of each check with a pass or fail. With the Basic plan, it prints as an A4 calculation note.
A class 1 section with A = 11,250 mm², iy = 127.4 mm, iz = 74.9 mm and Wy,pl = 1,383,000 mm³, on curves b and c, in fy,k = 235 N/mm², under a compression NEd = 800 kN and end moments of 120 kNm and zero about the strong axis, 4,000 mm long and pinned at both ends in both planes, with lateral-torsional buckling prevented. These are the module's own results for its worked example, computed when this page was built.
| Input | Value | Ref. |
|---|---|---|
| Characteristic yield strength fy,k | 235 N/mm² | § t.1 |
| Modulus of elasticity E | 210000 N/mm² | § 2.2 |
| Section class under these forces | 1 | § t.4 |
| Area of the section A | 11250 mm² | |
| Radius of gyration, strong axis iy | 127.4 mm | |
| Radius of gyration, weak axis iz | 74.9 mm | |
| Plastic section modulus, strong axis Wy,pl | 1383000 mm³ | |
| Buckling curve, strong axis | b | |
| Buckling curve, weak axis | c | |
| Resistance factor γM1 | 1.05 | § 4.1.3 |
| The axial force is | Compression | |
| Design axial force NEd | 800 kN | |
| Largest moment about y along the member My,Ed | 120 kN·m | |
| Moment diagram | End moments only — the diagram is linear | |
| Smaller end moment |Mmin| | 0 kN·m | |
| The two end moments have | The same sign at both ends | |
| Bending | About the strong axis only | |
| Buckling lengths | From the end conditions and intermediate supports | |
| Length of the member l | 4000 mm | |
| Ends, buckling about the strong axis y | Held against sway — both ends pinned | |
| Intermediate supports against buckling about y ny | 0 | |
| Ends, buckling about the weak axis z | Held against sway — both ends pinned | |
| Intermediate supports against buckling about z nz | 0 | |
| Lateral-torsional buckling | Prevented | § 4.5.2 |
| Step | Value | Ref. |
|---|---|---|
| Characteristic yield strength | fy,k = 235 N/mm² | § t.1 |
| Axial resistance of the sectionA·fy,k/γM1. | NRd = 2,517.9 kN | § 4.1.3 |
| Moment resistance, strong axisfy,k·Wy/γM1. | My,Rd = 309.5 kN·m | § 4.1.3 |
| Step | Value | Ref. |
|---|---|---|
| Reduced plastic momentMy,pl,Rd·(1 − n), n = NEd/Npl,Rd = 0.3177. | My,N,Rd = 211.2 kN·m | |
| Section, bending and axial forceMy,Ed ≤ My,N,Rd | η = 0.568 · Pass57 % of the capacity used |
| Step | Value | Ref. |
|---|---|---|
| Buckling length, strong axisk·l with k = 1.00 — held against sway — both ends pinned. | lK,y = 4,000 mm | |
| Buckling length, weak axisk·l with k = 1.00 — held against sway — both ends pinned. | lK,z = 4,000 mm | |
| Relative slenderness, strong axis(lK,y/iy)/λE, iy = 127.4 mm, λE = π·√(E/fy,k) = 93.91. | λ̄K,y = 0.3343 | |
| Relative slenderness, weak axis(lK,z/iz)/λE, iz = 74.9 mm. | λ̄K,z = 0.5687 | |
| Buckling resistance, strong axisχK·A·fy,k/γM1, curve b, χK = 0.9514. | NK,y,Rd = 2,395.4 kN | § 4.5.1 |
| Buckling resistance, weak axisχK·A·fy,k/γM1, curve c, χK = 0.8038. | NK,z,Rd = 2,023.9 kN | § 4.5.1 |
| Elastic critical load, strong axisπ²·E·Iy/lK,y². It sets the amplification 1/(1 − NEd/Ncr) of the moment. | Ncr,y = 23,653 kN | |
| Elastic critical load, weak axis | Ncr,z = 8,176 kN |
| Step | Value | Ref. |
|---|---|---|
| Moment factor, strong axis | ωy = 0.6000 | |
| Axial termThe smaller buckling resistance. | NEd/NK,Rd = 0.3953 | |
| Strong-axis term, amplified | ωy·My,Ed/((1 − NEd/Ncr,y)·MD,Rd) = 0.2408 | |
| Stability, bending and compressionNEd/NK,Rd + amplified moment terms ≤ 1 | η = 0.636 · Pass64 % of the capacity used |
Verified clause by clause against SIA 263:2013 and against independent calculations used on real projects, before release.
The linear interaction holds for any section, since it lies inside the true plastic interaction curve. For a rolled I or a solid rectangle, the dedicated modules use that section's own curve and are less severe.
When lateral-torsional buckling is not prevented. The module cannot derive the critical moment from the properties entered, so it takes McrD from a fuller calculation.
The full calculation is shown on screen, free and without an account. A print-ready A4 calculation note is part of the Basic plan.
Norm: SIA 263:2013 · Page updated: 28 October 2026