Timber Bolted Connection
Determine the allowable load per bolt (Z' = Z · adjustment factors) for single-shear and double-shear bolted connections in sawn lumber. Evaluates all applicable yield modes (Im, Is, II, IIIm, IIIs, IV) per NDS 2024 Section 12.3.1 to find the governing reference design value Z. Applies group action factor (Cg), geometry factor (CΔ), and other NDS adjustments to obtain the adjusted design value Z'.
What this calculates
Reference lateral design value Z from the governing yield mode, group action factor Cg per NDS Appendix E, geometry factor CΔ per Section 12.5.1, adjusted design value Z' = Z · CD · CM · Ct · Cg · CΔ, and total connection capacity Z'·n for the bolt group. Reports the governing yield mode.
Inputs
Nominal bolt diameter
Thickness of the main (thicker) member
Thickness of the side member
Dowel bearing strength of the main member
Dowel bearing strength of the side member
Bending yield strength of the bolt (typically 45000 psi)
Number of bolts in the connection
Number of rows of bolts (for group action factor)
Load duration factor
Outputs
Reference lateral design value per bolt (governing yield mode)
The yield mode that governs (Im, Is, II, IIIm, IIIs, or IV)
Group action factor per NDS Appendix E
Geometry factor for end/edge/spacing
Z times all adjustment factors
Total adjusted capacity for all bolts
Methodology
Bolt yield modes per NDS 2024 Section 12.3.1 (Equations 12.3-1 through 12.3-6) using dowel bearing strengths Fe (parallel and perpendicular to grain) from NDS Table 12.3.3. The governing Z is the minimum of all yield mode values. Group action factor Cg accounts for unequal bolt load distribution in rows of bolts per NDS Appendix E. Geometry factor CΔ checks end distance, edge distance, and spacing requirements per Section 12.5.1. Total connection capacity is Z' × number of bolts.
Code References
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