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Anchor bolt design / "effective bearing length" meaning & calculat

Anchor bolt design / "effective bearing length" meaning & calculat

Anchor bolt design / "effective bearing length" meaning & calculat

I am trying to verify some equations relating to the design of anchor bolts on the saddle of a horizontal vessel in a seismic / wind load design situation.  

My understanding is that anchor bolt design is governed by one of three load cases including: longitudinal load, shear load, and transverse load.

Assuming these are correct, my question lies in the transverse load case.  The book I'm using has a 6 step method of analyzing the transverse load on the anchor bolts.  I have not been able to verify the author's design method or any of the equations he uses.  

If anyone could inform me the origin of the following equation and any references I could find additional information, I would greatly appreciate it.  

I am mainly confused about what is called the "bearing length" (Y)  It is calculated by solving the following equation for Y:

Y^3 + K1*Y^2 + K2*Y + K3 = 0

where Y has units of (inches / cm / etc...) and K1, K2, K3 are all factors relating mainly to the moment force produced by the seismic / wind event.  

If my question is unclear, please respond and I will try to provide any additional information.

Thanks a million in advance!

RE: Anchor bolt design / "effective bearing length" meaning & calculat

I have not come across this particular equation.However all anchor bolt designs are governed by two criteria


The horizontal loads and moments translate to an uplift force on one set of anchor bolts and an equivalent compressive force on the opposite side of the foundation.
Additionally the shear forces are generally equally divided among all the anchor bolts.

The uplift of the anchor bolt is resisted by the "bond stress" between the concrete and and the anchor bolt.The length of the bolt required to be embedded inside the concrete is obtained by L= T/PI*D.

L= embeddment length
T= uplift force in anchor bolt
D= diameter of anchor bolt
PI= 3.14...

The length L is probably being designated as the "bearing length".

Hope you find this helpful.

All the best. Enjoy yourself!!


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