Anchor Bolt Sleeves
Anchor Bolt Sleeves
(OP)
I wanted to see how other engineers feel about the use of anchor bolt/anchor rod sleeves. These are normally plastic sleeves that create an annular space around the top of a cast-in bolt to create a tolerance for adjustment by essentially bending the bolt. The sleeve is filled with non-shrink grout after adjustment. Supposedly they're used all the time, particularly for machinery and equipment foundations.
I just don't like the concept, but I'm willing to listen.
I just don't like the concept, but I'm willing to listen.






RE: Anchor Bolt Sleeves
RE: Anchor Bolt Sleeves
RE: Anchor Bolt Sleeves
This isn't common, but can be useful in seismic detailing or where inelastic excursions are expected.
RE: Anchor Bolt Sleeves
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Anchor Bolt Sleeves
The ones I used were made by the machine manufacture.
essentially a steel pipe with a circular hollow disc on the bottom that housed a plate washer and the bolt head. This allowed for the unit to be cast in place and allowed for a few inches of adjustment in every direction. Pretty slick.
RE: Anchor Bolt Sleeves
I think i might be wrong here but I think Longer bolts do better for fatigue loading b/c of the % strain is less and the fatigue range goes down.
I think this might be the reason some machines use sleeves on the bolts.
RE: Anchor Bolt Sleeves
It is very important to address corrosion of exposed bolt with these.
RE: Anchor Bolt Sleeves
RE: Anchor Bolt Sleeves
RE: Anchor Bolt Sleeves
RE: Anchor Bolt Sleeves
http://www
RE: Anchor Bolt Sleeves
That being said, those risks can be reduced. Therefore, it still looks like a decent and innovative product. If the cost isn't too high, then I'd think it could work nicely.
RE: Anchor Bolt Sleeves
RE: Anchor Bolt Sleeves
1. Provide a "stretch length" for pretension.
If the anchor bolt needs a pretension, it needs a free stretch length so that the pretension load will not lose with time being due to the relaxing of bond between anchor rod and concrete.
2. It allows bending anchor rod to fit in base plate hole if it's out of alignment, although it's not recommended.
We normally use the black electric tape to wrap the anchor rod on the sleeve portion and fill the sleeve with grout after pretension. In this way we can maintain the contact between anchor rod and concrete for bearing type shear transfer, and it also provides the "stretch length" by debond the wrapping bond stress between anchor rod and concrete.
You can go to http://www.civilbay.com to download the anchor bolt design software for anchor bolt design example as per ACI 318-08 Appendix D with both Anchor Reinforcement and Seismic Ductility provision. It will show you the recommended sleeve sizing and how the sleeve can help to achieve anchor bolt ductility design.
The "stretch length" for anchor bolt ductility has been codified in the new ACI 318-11 Appendix D.
RE: Anchor Bolt Sleeves
Are you a contributor to the Civilbay website?
RE: Anchor Bolt Sleeves
What is the point of the tape? If you pretension the bolt before grouting, I see no reason to debond the bolt from the grout.
RE: Anchor Bolt Sleeves
To reply your inquiry, below is from ASCE " Wind Loads & Anchor Bolt Design for Petrochemical Facilities " section 4.3.4 Stretching Length on page 4-5
On a typical anchor bolt embedment, as a pre-load is placed upon the bolt, the bolt starts to shed its load to the concrete through its grip (bond) on the bolt. At that time, there exists a high bond stress at the first few inches of embedment. This bond will relieve itself over time and thereby reduce the pre-load on the bolt. Therefore, it is important that the bond be prevented on anchor bolts to be pre-tensioned. Bond on the bolt shaft can be prevented by wrapping the shaft with plastic tape or by heavily coating the bolt with grease immediately before placing concrete. Grout must not be allowed to bond to the anchor bolt. Tape the portion of the anchor bolt through the grout zone and to within one inch of the bolt head, below the sleeve ...
The bond between anchor rod and concrete is the unfavorable thing in anchor bolt design. Many engineers are surprised when they see the anchor rod is wrapped with black electric tape throughout the anchor rod all the way down to 2" above the head. It doesn't harm the anchorage at all, on the contrast, it gets the anchor bolt head engaged to the concrete right after applying tensile load, otherwise the anchor rod takes the load at top few inches and the head takes no load.
You can take a look at the ACI 318-08 Appendix D pullout resistance formula, it's just the anchor bolt head bearing, no bond stress along the anchor rod shaft.
I hope above will answer your inquiry.
The "stretch length" is recently codified in ACI 318-11 for ductile anchor design. I got a reply from the author of anchor bolt design software from http://www.civilbay.com and they say the "stretch length" will be updated in the ACI 318-11 version of anchor bolt design spreadsheet to reflect the anchor bolt ductility design for anchor bolt seismic application.
RE: Anchor Bolt Sleeves
I wouldn't use electrical tape in that zone due to concerns about corrosion. It seems to me the smooth tape would allow a path for moisture accumulation. The cementitious grout provides much better corrosion protection in the absence of the tape. Below the sleeve, I can see the tape being used.
RE: Anchor Bolt Sleeves
I got your point.
For anchorages which require pre-tension there normally exist cyclic tensile load or dynamic impact load pattern. The cyclic load pattern causes the loading/unloading of tensile force on anchor bolt even after the grouting of sleeve. For this reason the debond is still required after grouting.
With regard to corrosion, it's always an issue for outdoor structures regardless of using tape or not. The anchor bolt design software from http://www.civilbay.com provide users an option of using 1/8" anchor rod diameter reduction, as corrosion allowance, with reduced Ase value in both tensile and shear resistance calculation. That's the normal practice to go.
RE: Anchor Bolt Sleeves
RE: Anchor Bolt Sleeves
No complaints so far.
Mike Halloran
Pembroke Pines, FL, USA
RE: Anchor Bolt Sleeves
RE: Anchor Bolt Sleeves
That Deco bolt is interesting, I started out working on the design of oil refineries: for some stacks and big towers, we had some anchors fabricated where the nut was near the bottom of the tube and a long bolt screwed in place after the equipment was set and leveled on shims. The grout was dry-packed as we didn't have non-shrink back then, some got into the tubes but they didn't fill completely.
Michael.
Timing has a lot to do with the outcome of a rain dance.