Wood column and post
A solid sawn, glulam or SCL column in compression, tension and bending, to NDS 2024 3.6 to 3.9 and 15.4 with ASCE 7-22 combinations, in ASD or LRFD. The column is pinned at both ends of its height; the effective lengths per axis come from the buckling length coefficient and the unbraced lengths you enter.
Inputs of the wood column #
- Member: sawn lumber (species, grade, nominal size, or reference values entered), glulam (Table 5A stress class; the axial Ft and Fc are used) or SCL (manufacturer values). Axis 1 is the strong axis (dimension d), axis 2 the weak axis (b).
- Height and bracing: the column height, Ke (NDS Appendix G; 1.0 for pinned ends is prefilled), the unbraced lengths lu1 and lu2 for buckling about each axis (0 = the height) and the unbraced length of the compression edge for the beam stability of strong-axis bending (0 = the height).
- Loads: axial loads per load type (compression positive, tension negative) with their eccentricities e1 and e2, uniform side loads (wind on a post) about either axis over the height, and the area of holes at the net section for tension.
- Service conditions and load duration as in the beams.
Auto-design (editor toolbar) varies the sawn size (or glulam / SCL width and depth); grade when unlocked. Objectives: least wood (section area); lowest cost index. Kept unless you select them: grade. Every other input is kept; see Auto-design.
Checks performed #
| Check | Basis |
|---|---|
| Slenderness | le/d ≤ 50 (3.7.1.4), for members in compression |
| Compression | fc = P/A ≤ Fc' = Fc* CP, CP by Eq. 3.7-1 (c = 0.8 sawn, 0.9 glulam and SCL), the smaller CP of the two axes |
| Combined bending and compression | Eq. 3.9-3 (uniaxial or biaxial, with the stability limit Eq. 3.9-4); with an eccentric load Eq. 15.4-1 with Eq. 15.4-2 |
| Strong-axis bending stability | CL by Eq. 3.3-6 with le from the general values of Table 3.3.3; for glulam the lesser of CL and CV (x = 20 for the Southern Pine classes); RB ≤ 50 (3.3.3.7) |
| Tension | ft = T/An ≤ Ft' (3.8) |
| Combined bending and tension | Eqs. 3.9-1 and 3.9-2 (bending about one axis), Fb* without CL and Fb** without CV |
| Shear from side loads | fv = 3V/(2A) ≤ Fv' |
Drawings #
The drawing sheet (Drawing sheet / DXF buttons, and the report appendix) shows the column elevation with the axial loads by type onto the top, the side loads along the height, the height, the member mark and a callout with Ke, the unbraced lengths and the eccentricities, and the member section (b x d, species and grade or stress class). End fixity, brace locations between the ends, base and cap hardware are not part of the calculation and are not drawn; the sheet notes say so.
Limitations #
- Built-up and spaced columns (15.2, 15.3), round and tapered columns, and tension with bending about both axes (reported as not feasible) are outside the module. Fixed ends are represented through Ke.
- Checked against the NDS 2024 text: 3.6.3, 3.7.1 (Eq. 3.7-1, c = 0.8 / 0.9, le/d ≤ 50), 3.8, 3.9 (Eqs. 3.9-1 to 3.9-4), 15.4 (Eqs. 15.4-1, 15.4-2), 5.2.7 (glulam Ex,min / Ey,min for buckling about x / y), 5.3.7 (Cfu = (12/dy)^(1/9) on Fby), 8.3.6 (SCL volume factors). Corrected: the weak-axis eccentric term of Eq. 15.4-1 now carries the amplification 0.234 [(fb1 + fc 6e1/d1)/FbE]² (it was missing; the ratio was slightly low with eccentricity about both axes); the glulam volume factor of the Southern Pine classes uses x = 20; Eq. 3.9-1 uses Fb* with CV for glulam and Eq. 3.9-2 uses Fb** without CV for SCL; RB ≤ 50 is checked.
- The reference values (Supplement Tables 4A, 4B, 4D, 5A) stay marked [verify]: the NDS 2024 Supplement is not on disk (
research/DOCUMENTS_NEEDED.md). The SCL tension volume factor (8.3.6.2) is the manufacturer's: enter Ft already adjusted for it. - Side loads are uniform over the full height; deflection of the column is not checked.
Verification examples #
Published values of AWC Structural Wood Design Examples 2015/2018 Example E1.4 (as tabulated in the free Tekla Tedds verification example), Aghayere & Vigil, Structural Wood Design 2nd ed., Example 5.6 (as tabulated in the free calcs.com validation page), the NDS 2024 Appendix E sample solutions (the side members of bolted connections, ASD with all factors 1.0) and hand calculations in closed form (backend/tests/test_verify_wood_column.py). Published ASCE 7-16 snow loads are entered as S / 0.7 (ASCE 7-22 strength-level snow); in LRFD only the capacity is compared.
| Example | What it checks | Published / hand value | ILX Calcs |
|---|---|---|---|
| AWC-E1.4a | 4x4 SP No. 2 post, 10 ft, Ke = 1.0 | Fc* = 1450 psi, FcE = 357 psi, CP = 0.232, Fc' = 336 psi, P = 4120 lb | 1450, 356.6, 0.232, 336.3, 4120 |
| AWC-E1.4b | 6x6 SP No. 2 post (Table 4D), 10 ft | Fc* = 525 psi, FcE = 760 psi, CP = 0.801, Fc' = 421 psi, P = 12,725 lb | 525, 759.8, 0.801, 420.6, 12,723 |
| AV-5.6 | 6x6 DF-L No. 1, 12 ft, D 6800 + S 10,200 lb | ASD: P = 17,000 lb, FcE = 695 psi, CP = 0.502, capacity 17,463 lb; LRFD: FcE = 1042 psi, CP = 0.502, capacity 26,300 lb | 17,000, 695.5, 0.503, 17,497; 1040, 0.501, 26,206 |
| NDS-E.6 | SPF No. 2 2x4 and 4x4, NDS 2024 p. 175 | Ft' = 450 × 1.5 = 675 psi, ft at Z_NT' = 2,468 lb = 675 psi, Fv' = 135 psi | same |
| NDS-E.8 | Hem-Fir No. 2 2x4, p. 178 | Ft' = 525 × 1.5 = 788 psi, ft at Z_NT' = 3,470 lb, Fv' = 150 psi | same (787.5 psi) |
| NDS-E.9 | Southern Pine No. 2 2x4, pp. 178-179 | Ft' = 675 psi, Fv' = 175 psi | same |
| HAND-1 | 6x6 DF-L No. 1, 10 ft, D 6000 + L 10,000 lb | CP = 0.692, Fc' = 691.7 psi (ASD); CP = 0.640, Fc' = 1105.6 psi (LRFD) | same |
| HAND-2 | Same post, D 8000 lb and a 100 plf wind side load | Eq. 3.9-3 = 0.332 under D + 0.6W | same |
| HAND-3 | 2x6 DF-L No. 2 in tension | Ft' = 747.5 psi (ASD), 1291.7 psi (LRFD) | same |