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


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.


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

  1. I  am looking at rational design criteria for Anchor bolts

    1. Edge distance
    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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