Circular pattern anchor bolts 3

[engleprechaun]

Im am designing a monopole cellular comm. tower. The base plate has a circular pattern of 20 bolts (42 in dia.). I have been looking in both ACI 318-08 and AISC thrid edition. Both books seem to be geared toward square or rectangular patterns. Is there different methods used for a circular pattern? Also, I am having a hard time finding the definition if group anchor bolts versus single anchor bolts. Would I consider them as a group or on an individual basis? Thanks in advance for the help.

 

[engleprechaun]

I forgot one possible important consideration. There is a pattern plate or plate at the bottom of the bolts holding them together.

 

[CoryPad]

Here is the most detailed treatment I have seen.

http://www.risatech.com/products/dnloads/risatower/Technical_Manual_1.pdf

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[unclesyd]

CoryPad,

An excellent design paper.

unclesyd

 

[MotorVib]

unclesyd is right CoryPad that is an excellent design paper. How did you find it?

Chris


"In this house, we obey the laws of thermodynamics." Homer Simpson

 

[CoryPad]

I was studying the subject approximately 1 year ago and found it via Google.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[sdz]

Most bolt patterns are a rectangular layout so this is what ACI318 (and the Concrete Capacity Design method) is based on. But of course the pullout cone is round. You can go back to the background papers but especially "Fastenings to Concrete and Masonry Structures" By Comité euro-international du béton.
If however your anchors are more than 3*anchorage depth apart then the pullout cones will not interact and anchors can be treated individually.
I'm not convinced that the square based pyramid "pullout cone" was the best way to go but it does simplify calculations for rectangular layouts.

 

[dinjin]

A circular pattern is very typical of many ball and roller bearing designs that have bolt on races. I would think the
technology would be the same.

 

[Bribyk]

You might want to try Hilti's PROFIS software. It's free here (

http://www.us.hilti.com/holus/modul...=software+downloads&subtype=anchoring+systems

) and made for these design scenarios. I'm not affiliated with Hilti but found it very useful for designing plates fastened to concrete and I'm pretty sure it'll do circular patterns.

 

[sdz]

Is PROFIS geared toward cast in bolts?

 

[Bribyk]

It's more geared for Hilti's mechanical and epoxy anchors but I'd think some of the results would still be relevant, such as recommended plate thickness, shear cone interaction and bolt/anchor tension. Have a look through the user manual on the link above to see if it'll be of use to you.