Material and cross-section, shared by every verification. Change the verification above and these stay as they are.
Checks a rectangular solid-timber or glulam bar in axial compression at the ultimate limit state, to SIA 265:2021: buckling about both axes and the resistance of the cross-section. Every step shows its formula and the clause it comes from.
You enter the member (wood type, strength class, load duration, service class, b, h), the design compressive strength fc,0,d and the characteristic values fc,0,k and E0,05 from your copy of SIA 265, the role of the member, the design compressive force Nd, the buckling lengths about both axes (directly, or from the member length and end conditions), and any loss of section.
You get every intermediate value with its clause, the utilisation of each check with a pass or fail, and figures. With the Basic plan, it prints as an A4 calculation note.
A glulam column GL24h, b × h = 120 × 240 mm, in service class 1, with a design compressive force of 245 kN and buckling lengths of 5.20 m about y-y and 2.60 m about z-z. These are the module's own results for its worked example, computed when this page was built.
| Input | Value | Ref. |
|---|---|---|
| Wood type | Glulam | |
| Strength class | GL24h | |
| Load duration ηt | Short to permanent | § 2.2.6 |
| Service class ηw | 1 | § 3.2.1.3 t.4 |
| Section width b | 120 mm | |
| Section depth h | 240 mm | |
| Design compressive strength ∥ grain fc,0,d | 14.5 N/mm² | § 3.4.2.2 t.9 |
| Characteristic compressive strength ∥ grain fc,0,k | 24 N/mm² | § Annexe B |
| Modulus of elasticity, 5% fractile E0,05 | 9400 N/mm² | § Annexe B |
| Role of the member λlim | Main load-bearing element | § 4.2.8.4 |
| Design compressive force Nd | 245 kN | |
| Buckling length given by | Entered directly | |
| Buckling length about y-y lk,y | 5200 mm | |
| Buckling length about z-z lk,z | 2600 mm | |
| Section loss | None — gross section |
| Step | Value | Ref. |
|---|---|---|
| Gross section areaA = b · h | A = 28,800 mm² |
| Step | Value | Ref. |
|---|---|---|
| Radius of gyration about y-yiy = 0.289 · h | iy = 69.36 mm | |
| Radius of gyration about z-ziz = 0.289 · b | iz = 34.68 mm | |
| Buckling length about y-y | lk,y = 5,200 mm | |
| Buckling length about z-z | lk,z = 2,600 mm | |
| Slenderness about y-yλy = lk,y / iy | λy = 74.97 | |
| Slenderness about z-zλz = lk,z / iz | λz = 74.97 | |
| Governing slenderness (y-y)λ = max(λy, λz) | λ = 74.97 | § 4.2.8.4 |
| Straightness factor | βc = 0.10 | § 4.2.8.3 |
| Relative slendernessλrel = (λ/π)·√(fc,0,k / E0,05), not less than 0.30 | λrel = 1.2058 | § 4.2.8.4 (34) |
| Auxiliary factork = 0.5·[1 + βc·(λrel − 0.3) + λrel²] | k = 1.2723 | § 4.2.8.2 (31) |
| Buckling coefficientkc = 1 / (k + √(k² − λrel²)), with k from equation (31) above | kc = 0.5959 | § 4.2.8.2 (30) |
| Design resistancefRd = kc · fc,0,d · ηt · ηw | fRd = 8.640 N/mm² | § 4.2.2.1 (10) |
| Design stressσc,0,d = Nd / A | σc,0,d = 8.507 N/mm² | |
| Buckling about y-yσc,0,d ≤ kc · fc,0,d | η = 0.985 · Pass98 % of the capacity used | § 4.2.8.1 (29) |
| Step | Value | Ref. |
|---|---|---|
| Cross-section resistance, buckling ignoredNRd = A · fc,0,d · ηt · ηw | NRd = 417.6 kN | § 4.2.2.1 (10) |
| Cross-section resistanceNd ≤ NRd | η = 0.587 · Pass59 % of the capacity used | § 4.2.2.1 (10) |
Verified clause by clause against SIA 265:2021 and against independent calculations used on real projects, before release.
The one with the larger slenderness. The module computes both and checks buckling about the governing axis; in the worked example both slendernesses are equal.
SIA 265 clause 4.2.8.4 forms the relative slenderness from the characteristic values, so E0,05 is entered as the characteristic value.
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 265:2021 · Page updated: 20 October 2026