Example of Concrete Anchor Bolt Design Calculation – Part-7: Determining Pryout Strength of Anchor in Tension

In this part of the concrete anchor bolt design calculation example we will calculate the concrete pry out strength under shear force applied to the structural cast in place foundation anchor bolt of the column shown in the Figure-1 and 2 of the Part-1 of this design calculation series.

What is Concrete Pryout Strength?

This is something related to the coming out of the short and stiff anchors by breaking or chipping the concrete at the direction opposite to the applied shear force to the column.

Design Calculation

The code ACI 318 Appendix D gives the following equation:

φVcpg=kcpNcbg ………………D-31

Where,

Φ – Strength reduction factor for pryout strength and its value for non-reinforcement in tension is 0.70

VcpgPryout strength

kcpFactor, which has value =2  for the anchor longer than 2.5 inch.

Ncbg – Concrete breakout strength in tension (=20694.6131 lb, Refer Part-2) for the anchor group.

Now, by putting all the values we get the pryout strength,

Φ Vcpg = 28972.45 lb

Summary of Calculated Strength Values in Shear

Through the part-5, Part-6, and this part we have come out with the following shear strength values:

Nominal material strength in for the anchors (Φ Vsa) = 65130 lb

Concrete breakout strength for the anchor group (Φ Vcbg) =10821.297 lb

Pryout strength of the anchor group (Φ Vpn) =28972.45 lb

Out of these three strength values the smallest one will be the design strength.

So, the design strength in shear = 10821.297 lb

From the problem statement (part-1), you can observe that applied factored shear force to the column = 2300 lb.

Since, design strength in shear is much lower than the factored applied shear force, so, the anchor bolts are safe under shear loading.

In the next part (Part-8) of this concrete anchor foundation bolt design calculation example we will see the interaction of tensile and shear forces according to the ACI 318D.

Shibashis Ghosh

Hi, I am Shibashis, a blogger by passion and engineer by profession. I have written most of the articles for mechGuru.com. For more than a decades i am closely associated with the engineering design/manufacturing simulation technologies.
Disclaimer: I work for Altair. mechGuru.com is my personal blog. Although i have tried to put my neutral opinion while writing about different competitor's technologies, still i would like you to read the articles by keeping my background in mind.

2 Replies to “Example of Concrete Anchor Bolt Design Calculation – Part-7: Determining Pryout Strength of Anchor in Tension”

1. Thilakesh Kumar says:

2. Thilakesh Kumar says:

I  am looking at rational design criteria for Anchor bolts

1. Edge distance
2.
Embedment length
3. Sleeve requirements
4. Projection of anchor above
grout calculations
5. Pretensioning
6. Materials used for anchor bolts
in India
7. Rational design basis

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