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CSA O86:19NBCC 2015Wood Design Manual 2017American Wood Council Technical Report 14

Wood Column

Column loads link from beam reactions above to footing calculations below automatically - change a load once and everything downstream updates. Design wood columns and studs to CSA O86:19 with NBCC 2015 load combinations: axial compressive resistance, combined bending plus axial interaction, biaxial buckling, shear, and bearing perpendicular to grain.

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What it calculates

The Calcs.com timber column calculator to CSA O86 enables the fast and accurate design of wood columns and studs to Canadian standards. With support for dynamic load linking between beams and columns, easily design accurate and quality engineered columns.

Code standards

  • CSA O86:19
  • NBCC 2015
  • Wood Design Manual 2017
  • American Wood Council Technical Report 14

How it calculates

Structural model and load combinations

The calculator models the wood column as a member under combined axial compression and biaxial bending. Loads are entered by type - dead (D), live (L), snow (S), wind (W) - and the calculator generates all governing NBCC 2015 / CSA O86:19 strength load combinations. Bending moments can be entered directly or received via load linking from beam calculations above.

Axial compressive resistance (CSA O86:19 Cl.6.5.5.2.4)

Factored compressive resistance P_r is computed from the characteristic compressive strength F_c parallel to grain, adjusted by:

  • K_H - system factor
  • K_Scp - service-condition factor for compression
  • K_T - treatment factor
  • K_c - slenderness factor, derived from the slenderness ratio C_c for each axis

The slenderness ratio C_c is computed for both the X-axis and Y-axis independently per Cl.6.5.5.2.2. The governing (largest) ratio controls the slenderness factor K_c, reducing compressive resistance for slender members. For multi-ply columns, Cl.6.5.5.4 applies additional reduction factors based on the ply connection method.

compression utilization = P_f / P_r ≤ 1.0

Bending moment resistance (CSA O86:19 Cl.6.5.3.1 and Cl.7.5.6.5.1)

Factored bending resistance M_r is computed for both the X-axis and Y-axis using adjusted bending strength F_b. The lateral stability factor (Cl.7.5.6.5.1) accounts for buckling of the compression face and is applied independently for each axis.

Combined bending and axial interaction (CSA O86:19 Cl.7.5.12)

When both axial compression and bending moments are present, the calculator checks the biaxial interaction equation per CSA O86:19 Cl.7.5.12, using the formulation from AWC Technical Report 14:

interaction utilization = P_f/P_r + M_fx/M_rx + M_fy/M_ry ≤ 1.0

Where M_fx and M_fy are the factored bending moments about the strong and weak axes respectively. This single interaction check governs over the individual axial and bending utilizations when moments are present.

Shear resistance (CSA O86:19 Cl.6.5.4.3)

Shear resistance is checked independently for forces applied in each direction, using the same adjustment factors applied to the bending checks.

Bearing perpendicular to grain (CSA O86:19 Cl.6.5.6.2)

At the base of the column or wherever the member bears on a sill plate or other perpendicular-grain surface, factored bearing resistance Q_rp is computed from the characteristic compressive strength perpendicular to grain F_cp, adjusted for service condition and treatment.

Load linking

The column's axial reaction at its base is exported as a linked output to connected footing calculations. Axial load at the top can be linked from beam reactions above, so the full load path - beam to column to footing - updates automatically when any upstream input changes.

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Frequently asked questions

What design standard does this calculator use?
The calculator designs wood columns to CSA O86:19 (Limit States Design) with load combinations per NBCC 2015. Biaxial bending interaction follows CSA O86:19 Cl.7.5.12, which references American Wood Council Technical Report 14 for the combined bending-plus-axial interaction equations.
What are the key inputs?
Key inputs include the wood section (species, grade, and product type from the built-in database or a custom section), column height, number of plies, effective length factors for both axes, service condition (dry or wet), treatment, factored axial load, and bending moments about both axes from linked beam reactions or manually entered loads.
What checks and outputs does it produce?
The calculator checks factored compressive resistance parallel to grain (CSA O86:19 Cl.6.5.5.2.4), factored bending moment resistance about both axes (Cl.6.5.3.1 and Cl.7.5.6.5.1), combined bending-plus-axial interaction (Cl.7.5.12), shear in both planes (Cl.6.5.4.3), and bearing perpendicular to grain (Cl.6.5.6.2). Slenderness ratios for both axes are computed per Cl.6.5.5.2.2.
How does biaxial buckling work for multi-ply columns?
For multi-ply (built-up) columns, the calculator applies the multi-ply compressive resistance provisions of CSA O86:19 Cl.6.5.5.4, which reduce the effective compressive resistance based on how the plies are connected. Slenderness ratios are computed independently for the X-axis (bending the full built-up section) and Y-axis (buckling of individual plies), and the governing direction controls.
Can it handle combined bending and axial loading?
Yes. The combined bending-plus-axial check follows CSA O86:19 Cl.7.5.12 using the interaction equations from AWC Technical Report 14. Moments can be entered directly or linked from beam reactions above the column. Both strong-axis and weak-axis moments are included in the interaction equation simultaneously.
Does this calculator support load linking with beam and footing calculations?
Yes - axial load from beam reactions above links directly into the column, and the column reaction at its base links to connected footing calculations. Change a load or span in a beam above and the column and footing calculations below update automatically.

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