Anchor Bolt Sleeve 8

[AbhijitM]

Hello,

Fan manufacture drawing shows anchor bolt with Sleeve. My question is, what is the reason to provide sleeve?

Thanks,

 

[csd72]

Is this a proprietary chemical anchor with a cavity sleeve or is this a through bolt with a steel pipe sleeve?

csd

 

[AbhijitM]

Its a through bolt with steel Pipe sleeve and bolt is J-type

 

[civilperson]

J type bolts are not good in tension, but the steel indicates a pretensioning of the bolt.

 

[AbhijitM]

Does it means Steel fails first before the concrete cracks???

 

[civilperson]

No, the J bolt has the inner curve concrete crush and then fail. Steel yield/failure is desirable as it is ductile and as a weak spot or strength fuse.

 

[JJPellin]

The purpose of the sleeve is to provide a longer free length of stud to be stretched. The amount of stress imposed on the stud is limited by the strength of the stud. But the amount of strain (stretch) can be increased by increasing the length of stud which is under this stress. A greater stretch provided better certainty of maintaining the stud in tension under changing conditions. For studs holding down rotating machinery (pumps, compressors and turbines) we would normally require a free length of stud of at least 5 stud diameters to ensure a consistent clamping force holding the machine down to the foundation. In applications with the possibility of very high cyclical loads such as a reciprocating compressor, we would want even longer free lengths on the studs.

Johnny Pellin

 

[AbhijitM]

Thanks Johnny, This explanation is very useful to me. Thanks!!

Abhijit

 

[AbhijitM]

Thanks Johhny, How to decide sleeve pipe diameter. Can we use, Bolt Diameter + 1/2".
To hold down FD & ID Fans (Centrifugal), we are using bolts diameter ranging from 7/8" to 1.5" Dia bolts with varing embedment lengths (at least 12"). Also can we call sleeve length is 1/2 or 2/3 of embebment length of Anchor bolt. For example, for 7/8" Dia. AB with 12" embedment, can we call a Sleeve of 1.375" Dia with 4 to 6" length. Your help is appreciated.

Thanks,

 

[JJPellin]

In our machinery installations, the sleeve is used to keep the stud free from the concrete block and the grout. Once the base is installed and grouted in, the sleeve does not see any loads. So, for our installations, we really don't care how much clearance there is between the sleeve and the stud, as long as the stud is free to stretch. I would base the length of the sleeve on the diameter of the stud rather than the amount embedded. As I noted before, for general purpose machinery (such as FD / ID fans) would want a sleeve length of 5 stud diameters. So, for a 7/8" stud, I would want a sleeve at least 4-3/8" long. I am not an expert on the proper amount of embedment as this depends on the style of stud, the grade of concrete and whether the stud is connected to the rebar in the foundation block. I will leave questions of embedment to those with expertise in that area.

If you are referring to a sleeve that is above the base plate to provide the free length of stud above the surface of the block, I will also have to defer to other experts. This would place the sleeve in compression making the size of the sleeve important.


Johnny Pellin

 

[hokie66]

Johnny's advice is good, but just to add another thought, over sized sleeves are sometimes used for horizontal adjustment. Why don't you ask the fan manufacturer what he wants and why?

 

[Lion06]

I think this is a bad detail. As civilperson points out, J-bolts are not good in tension. If the idea of the sleeve is to allow the bolt to stretch, it is obvioiusly under tensile loads. J-bolts are bad in tension when the entire bolt is cast in concrete. I can only imagine that it is worse when only the hook is cast in concrete. I would try to get a nut welded on the end of the rod.

 

[Zambo]

I agree with hokie66, it seems that the drawing doesn't indicate what the requirement is. Is there a required tension or torque for the bolt? Is it possible that the sleeve is to prestress the concrete?

 

[AbhijitM]

I agree, J bolt is not good in tension and so we have AB with Heavy Hex Nut. The Sleeve is not above the surface of block so sleeve will not see any compression. Anchor bolt is designed using ACI Appendix D which does not consider sleeve. Since manufacture shows sleeve, it is good to get more info from them. I also agree with JJPellin's explanation on sleeve to get more strain/stretch and generally this is what manufacture want to see. In general applications, 5 times diameter of sleeve is acceptable. So I will design anchor bolt with nut using ACI Appendix D and provide sleeve 5 times sleeve diameter rather than provding sleeve whole embedment length of AB. Does it make sense to you guys. Any comments??
Thanks,

 

[csd72]

You should start the embedment depth at the bottom of the sleeve.

csd

 

[Lion06]

csd-
I think as long as you provide a nut with a washer on the anchor rod, you don't have to worry about the sleeve since the anchor rod is anchored entirely by the nut and doesn't require any develpment of bond stresses from concrete to rod. The failure cone should be equal to a failure cone without the sleeve (provided the sleeve isn't overly large in diameter).

 

[AbhijitM]

I agree with StructuralEIT and also try to get extra strain capacity by providing a sleeve, As JJPellin mentioned sleeve will give more strain/stretch. So its good idea to Design AB per ACI-Appendix D and provide a sleeve as short as possible rather than whole embedment length of AB.

 

[csd72]

Check the bearing stress from the nut onto the surrounding concrete, I think you will find it far exceeds allowable at full bolt tension.

A nut is sized to transfer the full tension against a steel plate, not concrete.

csd