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Calcimator

Timber Connection Calculator

Design bolted timber connections per NDS: calculate reference design values, group action factor, and connection capacity.

Inputs

mm
mm

NDS Supplement Table 12A: DF-L G=0.50; Southern Pine G=0.55; SPF G=0.42; Hem-Fir G=0.43

bolts
(1=parallel, 2=perp.)
mm

NDS §12.3: min spacing parallel to grain 4D; perp. to grain 3D; end distance 4D (full) or 2.5D (reduced)

Results

Total Connection Capacity

5,801.38 kN

Spacing Adequate?

1 (1=yes, 0=no)

Reference Design Value (Z)1,495.2 kN
Adjusted Capacity per Bolt1,450.34 kN
Group Action Factor (Cg)0.97
How to Use This Calculator
  1. Select the wood species and connection type (nails, bolts, screws, or timber rivets).
  2. Enter the fastener diameter, length, and number of shear planes.
  3. Input the applied lateral and withdrawal loads in lbs.
  4. Review the Design Value per Fastener and the Number of Fasteners Required.
  5. Apply adjustment factors for moisture content, temperature, and load duration per NDS.

How the result changes with Bolt Diameter

Bolt DiameterTotal Connection CapacitySpacing Adequate?
7.93,819.24 kN1 (1=yes, 0=no)
136,284.82 kN1 (1=yes, 0=no)
188,702.06 kN1 (1=yes, 0=no)
239,668.96 kN0 (1=yes, 0=no)

What each input means

Bolt Diameter
Nominal diameter of each bolt. Common sizes: 10, 12, 16, 20 mm.
Main Member Thickness
Thickness of the main wood member receiving the bolt.
Specific Gravity (G)
Specific gravity of the wood species per NDS Supplement Table 12A. Douglas Fir-Larch G=0.50; Southern Pine G=0.55; Hem-Fir G=0.43; Spruce-Pine-Fir (SPF) G=0.42; Ponderosa Pine G=0.43. G used in NDS yield limit equations.
Number of Bolts
Total number of bolts in the connection.
Load Direction
1 = Load parallel to grain (stronger), 2 = Load perpendicular to grain.
Bolt Spacing
Center-to-center spacing between bolts in a row per NDS §12.3. Minimum loaded end distance: 4D parallel to grain; minimum bolt spacing: 4D for parallel-to-grain loading; 3D for perpendicular. Group action factor Cg reduces capacity for multiple bolts.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Bolt Diameter = 12, Main Member Thickness = 89, Specific Gravity (G) = 0.5, Number of Bolts = 4 = 6 input(s) provided
  2. Calculate Total Connection Capacity
    Total Connection Capacity
    5801.376 = 5801.376
  3. Calculate Spacing Adequate?
    Spacing Adequate?
    1 = 1
  4. Calculate Reference Design Value
    Reference Design Value
    1495.2 = 1495.2
  5. Calculate Adjusted Capacity per Bolt
    1450.344 = 1450.344

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