Enter the hole diameter, the embedded length, and the average bond stress (bond strength) into the calculator to estimate the bolt (anchor) pull-out force. You can also enter any 3 values to calculate the missing variable.
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Bolt Pull Out Force Formula
The following simplified equation is used to estimate the bolt (anchor) pull-out force when failure is governed by bond along the embedded cylindrical surface (assumes a uniform average bond stress).
F_{po} = \pi D L MF- Where Fpo is the bolt pull out force (lb-f, when D and L are in inches and MF is in psi)
- D is the diameter of the hole (in)
- L is the length (embedment) of the hole (in)
- MF is the average bond stress (bond strength) between the grout/adhesive and the substrate (psi)
- ≈ 600 psi (example only) for an epoxy-to-concrete bond
- ≈ 1600 psi (example only) for an epoxy-to-steel bond
To calculate a bolt pull-out force, multiply π by the diameter and the embedded length, then multiply by the average bond stress (bond strength).
What is a Bolt Pull Out Force?
Definition:
A bolt pull-out force is the axial (tensile) force required to pull an anchored bolt out of the material it is embedded in. In many simplified models it is governed by bond (shear) stress along the embedded surface, but actual capacity can also be limited by base-material breakout, adhesive failure, or steel failure depending on the anchorage system.
How to Calculate Bolt Pull Out Force?
Example Problem:
The following example outlines the steps and information needed to calculate the Bolt Pull Out Force.
First, determine the diameter of the hole. In this example, the hole diameter is 2.5 inches.
Next, determine the length of the hole. In this case, the length is 5 inches.
Next, determine the average bond stress (bond strength). For this problem, assume an epoxy-to-concrete bond stress of 600 psi.
Finally, calculate the bolt pull out force using the formula above:
Fpo = π*D*L*MF
Fpo = 2.5*3.14159*5*600
Fpo = 23,561.925 lb-f
