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Calcimator

Timber Connector Design Calculator

Bolt count, spacing, and capacity for timber connections using NDS lateral design values.

Inputs

lbs
in
in

Results

Bolts required

7

Single bolt capacity

980 lbs

≈ 6 adults

Total connection capacity5,831 lbs
Demand/capacity ratio0.86
Group action factor (Cg)0.85
Bolt diameter0.75 in
Min bolt spacing (in row)3 in
Min row spacing3 in
Min end distance5.25 in
Min edge distance1.13 in
Min member width3 in
How to Use This Calculator
  1. Enter Design load, Bolt diameter, and Wood species.
  2. Set Load duration, Main member thickness, and Side member thickness.
  3. Review Bolts required and Single bolt capacity (lbs).
  4. Use Total connection capacity (lbs) and Demand/capacity ratio to inform your decision.

How the result changes with Design load

Design loadBolts requiredSingle bolt capacity
10,09014980 lbs
35,06546980 lbs
65,03586980 lbs
90,010118980 lbs

What each input means

Design load
Total lateral load the connection must resist.
Bolt diameter
0 = 1/2", 1 = 5/8", 2 = 3/4", 3 = 7/8", 4 = 1".
Wood species
0 = Douglas Fir-Larch, 1 = Southern Pine, 2 = Eastern White Pine, 3 = Red Oak.
Load duration
0 = Normal (Cd=1.0), 1 = Snow (1.15), 2 = 7-day construction (1.25), 3 = Wind/seismic (1.6).
Main member thickness
Thickness of the main (thicker) timber member.
Side member thickness
Thickness of the side (thinner) member or steel plate.

What each result means

Bolts required
Number of bolts needed including group action factor.
Single bolt capacity
Adjusted lateral design value per bolt (Z').
Total connection capacity
Sum of all bolt capacities with group action factor.
Demand/capacity ratio
Design load / connection capacity. Must be ≤ 1.0.
Group action factor (Cg)
Reduction factor for multiple bolts in a row.
Bolt diameter
Selected bolt diameter.
Min bolt spacing (in row)
Minimum spacing between bolts along the grain (4D).
Min row spacing
Minimum spacing between rows of bolts (4D).
Min end distance
Minimum distance from bolt to loaded end (7D for tension).
Min edge distance
Minimum distance from bolt to edge (1.5D loaded edge).
Min member width
Minimum timber width for single-row bolt pattern.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Design load = 5000, Bolt diameter = 2, Wood species = 0, Load duration = 0 = 6 input(s) provided
  2. Calculate Bolts required
    Bolts required = ceil(designLoadLbs / (allowableZ * Cg))
    7 = 7
  3. Calculate Single bolt capacity
    Single bolt capacity = adjustedZ * Cd
    980 = 980
  4. Calculate Total connection capacity
    Total connection capacity = round(boltsNeeded * allowableZ * Cg)
    5831 = 5831
  5. Calculate Demand/capacity ratio
    Demand/capacity ratio = designLoadLbs / connectionCapacity
    0.857 = 0.857

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.

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