Anchor bolt design / "effective bearing length" meaning & calculat 2

[dannyo]

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!

 

[ishvaaag]

Have no idea from the equation comes, may be akin to some work in sectional analysis and be related to find which of the bolts are in tension in the contraption. It may be a length that gives the lenght in the "section" that is compressed (more rarely in tension, following the label).

 

[dannyo]

On the drawing, the effective bearing length looks to be the length of a triangular load (uniformly increasing - greatest on the outside of the base plate) from a point designated as the "pivot point" to the end of the base plate (covering a distance of "Y&quot. This load is shown to be acting up on the base plate. There is also a tension force shown acting down on the other (opposite) side of the base plate.

Does this help any? If not, do you know any good references for anchor bolt design?

 

[IJR]

I am not sure I understood your problem but the following might put some bees in line

My assumption is you are looking at a page where the column is subjected to moment and axial force(M+N), and the moment is considerably large.

If this is true then a part of your plate is in tension and a part is in compression. Since bearing is not possible in zones of tension then yes you have only a part of plate in bearing-HENCE EFFECTIVE BEARING.

Tension will be carried by anchor bolts.

In the situation I have described a cubic equation always arises.-QUBIC EQUATION COMES FROM EQUILLIBRIUM CONSIDERATIONS FOR THIS CASE

Please read Omer W.Blodgett's book "Design of welded Structures" for a better feel

regs
IJR

 

[KRH]

Dannyo :

Its seems that your equations came from O.W. Blodgett's book "Design of Welded Structures" p.3.3-10 eqn (13)

The book is available from Lincoln Arc Company.

KRH

 

[dannyo]

KRH:

Actually, I found them in the "Pressure vessel design manual" by Dennis Moss. In previous dealings with this book, I have learned to take his "knowledge" with a bit (quite a bit) of skepticism. Being a typical curious (and cautious) engineer I am wanting (mainly) to understand the origins / derivation of the equations as to verify their correctness.

Thanks for the reference; I'll definitely check it out!