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Method & Assumptions

Equations used by this preliminary sizing tool

Fastener shear

Uniform load sharing between identical fasteners and shear planes.

R = n · m · (πd²/4) · Fsu,f

Pull-out / pull-through

The lower of fastener tensile capacity and sheet punching-shear capacity governs.

R = n · min[(πd²/4)Ftu,f ; πDh·t·Fsu,s]

Net-section tension

A straight critical section through the specified number of holes is assumed.

R = (w − nh·d) · t · Ftu,s

Bearing

Projected bearing area is summed for all load-sharing fasteners.

R = n · d · t · Fbru

Shear tear-out

Two shear planes per critical edge fastener with ligament length e − d/2.

R = ne · 2(e − d/2) · t · Fsu,s

Assessment convention

  • Utilization = applied load / allowable load
  • Reserve Factor: RF = allowable load / applied load
  • Margin of Safety: MS = RF − 1
  • Failure modes are evaluated independently; interaction is not included.
Preliminary sizing tool only. Verify material allowables, load distribution, geometry definitions, interaction effects and all applicable certification or company requirements before using results for design substantiation.
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Parameters

Geometry, loads and allowables

Design loads

Fastener pattern

Sheet geometry

Measured from hole center to loaded edge.

Allowables

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Results

Strength ratios and margins
Overall status
● PASS
Critical mode
–
Minimum RF
–
Minimum MS
–

Fastener Failure Modes

Failure mode Demand Allowable Utilization RF MS Status

Sheet Failure Modes

Failure mode Demand Allowable Utilization RF MS Status