Please refer the problem statement and the part-1, part-2 of this cast in place concrete anchor bolt design calculation example so that you will be in phase with this part (part-3) of the calculation. Here we will calculate the pull out strength of the concrete anchor according to the ACI 318 Appendix D codes.

**What is Anchor Pullout Strength?**

As the name suggests, it is the force required to uproot a anchor out of the concrete.

**Calculation**

According to ACI codes, the pull out strength of the group of anchors is given by

*φN*_{pn}=8nψ_{c,P}A_{brg}f’_{c}…………………………………..D-14

Where,

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

ψ_{c,P }- Modification factor for pullout strength based on the presence of concrete cracks, for the concrete with cracks at service load level **ψ**_{c,P}=1.

n – Number of anchor bolts, in our case **n=4.**

A_{brg} – Net bearing area of the head of anchor bolt in square inch, in our case **A**_{brg}=0.654 Square inch.

f’_{c} – The concrete’s specified compressive strength in psi, in our case **f’**_{c}=4000 psi.

So, by putting all the values in D-14, we get the pullout strength of the anchor group as

φN_{pn} =0.7*8*4*1*0.654*4000 lb

**= 58598.4 lb **

In the next part (Part-4) of the foundation anchor bolt design calculation example, we will discuss about calculating the concrete blow out strength in tension.

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