Data Source and Methodology
Authoritative Source: American Wood Council (AWC), National Design Specification (NDS) for Wood Construction, 2018 and 2024 Editions. See: AWC Connection Calculator and the NDS Chapter 12 (Dowel-Type Fasteners).
All calculations are strictly based on the European Yield Model (EYM) and dowel bearing strength equations prescribed by the AWC NDS. All adjustment factors follow NDS conventions where applicable. All computations performed by this tool are for ASD and are intended for preliminary design and educational use.
Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.
The Formula Explained
Dowel bearing strengths for bolts (wood member):
Fe parallel to grain: \( F_{e0} = 16600 \, G^{1.84} \) (psi)
Fe perpendicular to grain: \( F_{e90} = 6230 \, G^{1.45} \) (psi)
Angle to grain adjustment (Hankinson-type):
\[ F_{e\theta} = \frac{F_{e0}\,F_{e90}}{F_{e0}\,\sin^2\theta + F_{e90}\,\cos^2\theta} \]
Wood-to-steel single-shear yield modes (per-bolt, ASD form):
\[ Z_{Im} = F_{e\theta}\, d\, t \qquad Z_{II} = 1.15\, d\, t\, \sqrt{F_{yb}\, F_{e\theta}} \qquad Z_{III} = 2.30\, d\, t\, \sqrt{F_{yb}\, F_{e\theta}} \]
Controlling per-bolt capacity: \( Z = \min\left(Z_{Im}, Z_{II}, Z_{III}\right) \)
Adjusted per-bolt capacity: \( Z' = Z \times C_D \times C_M \times C_t \)
Total adjusted capacity for n bolts with group factor \(C_g\): \( Z_{\text{total}} = Z' \times n \times C_g \)
Glossary of Variables
- G: Specific gravity of wood species (dimension lumber basis).
- θ: Angle between load direction and wood grain (degrees).
- d: Bolt diameter (in).
- t: Wood member thickness bearing the bolt (in).
- Fyb: Fastener bending yield strength (psi).
- Fe0, Fe90, Feθ: Dowel bearing strength parallel, perpendicular, and at angle θ (psi).
- ZIm, ZII, ZIII: Nominal yield-mode capacities per bolt (lb).
- Z: Controlling nominal per-bolt capacity (lb).
- CD, CM, Ct: NDS adjustment factors for load duration, moisture, and temperature (—).
- Cg: Group action factor for multiple fasteners in a row (—).
- Z′: Adjusted per-bolt capacity (lb); Ztotal: total adjusted capacity (lb).
How It Works: A Step-by-Step Example
Frequently Asked Questions (FAQ)
Does this tool cover wood-to-wood connections?
The current release focuses on wood-to-steel single-shear. Wood-to-wood single-shear and double-shear configurations will be added next, following the same NDS framework.
Are spacing and edge distance requirements enforced?
The tool flags potential issues against typical NDS minimums. You must still verify exact geometry requirements (species, orientation, service class) with the current NDS tables.
How do I choose G (specific gravity)?
Use the NDS listed G for your species and product (e.g., Southern Pine, SPF). Do not use oven-dry values unless NDS specifies them.
What if the steel side plate is thin or slotted?
This version assumes a sufficiently thick steel plate. For thin plates, slotted holes, or oversize holes, consult NDS provisions and manufacturer data; capacities will differ.
Can I apply LRFD?
The results are ASD adjusted values. For LRFD, convert per NDS procedures and apply the appropriate resistance factors.
How precise are the angle adjustments?
The tool uses a Hankinson-type formula between parallel and perpendicular dowel bearing strengths, consistent with NDS. For critical designs, consider bounding cases (0° and 90°) as checks.
Is this a replacement for the AWC Connection Calculator?
No. It is a complementary educational tool. Always consult the latest NDS and use vetted software or hand-checks for final design.
Formula (LaTeX) + variables + units
F_{e\theta} = \frac{F_{e0}\,F_{e90}}{F_{e0}\,\sin^2\theta + F_{e90}\,\cos^2\theta}
Z_{Im} = F_{e\theta}\, d\, t \qquad Z_{II} = 1.15\, d\, t\, \sqrt{F_{yb}\, F_{e\theta}} \qquad Z_{III} = 2.30\, d\, t\, \sqrt{F_{yb}\, F_{e\theta}}
Dowel bearing strengths for bolts (wood member): Fe parallel to grain: \( F_{e0} = 16600 \, G^{1.84} \) (psi) Fe perpendicular to grain: \( F_{e90} = 6230 \, G^{1.45} \) (psi) Angle to grain adjustment (Hankinson-type): \[ F_{e\theta} = \frac{F_{e0}\,F_{e90}}{F_{e0}\,\sin^2\theta + F_{e90}\,\cos^2\theta} \] Wood-to-steel single-shear yield modes (per-bolt, ASD form): \[ Z_{Im} = F_{e\theta}\, d\, t \qquad Z_{II} = 1.15\, d\, t\, \sqrt{F_{yb}\, F_{e\theta}} \qquad Z_{III} = 2.30\, d\, t\, \sqrt{F_{yb}\, F_{e\theta}} \] Controlling per-bolt capacity: \( Z = \min\left(Z_{Im}, Z_{II}, Z_{III}\right) \) Adjusted per-bolt capacity: \( Z' = Z \times C_D \times C_M \times C_t \) Total adjusted capacity for n bolts with group factor \(C_g\): \( Z_{\text{total}} = Z' \times n \times C_g \)
- No variables provided in audit spec.
- AWC Connection Calculator — awc.org · Accessed 2026-01-19
https://awc.org/calculators/connection-calculator/
Last code update: 2026-01-19
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