what is this "hair pin" thing attached to anchor bolts?
what is this "hair pin" thing attached to anchor bolts?
(OP)
I have come across friends suggesting someone use hairpins in conjuction with anchor bolts in anchoring steel frames to foundations.
I have no single idea what this technique and its rationale are
I wont mind a little ancyclopaedic hint.
Thanks,IJR
I have no single idea what this technique and its rationale are
I wont mind a little ancyclopaedic hint.
Thanks,IJR






RE: what is this "hair pin" thing attached to anchor bolts?
In this case their goal would to raise the shear that may be transmitted from the bolt to the concrete and finally to make the bolt shorter.
However it isn't a practice familiar to me: the diameter of the bolt does not allow for good inspectable welds and the anchor must be of weldable material (this is normally the case).
prex
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RE: what is this "hair pin" thing attached to anchor bolts?
RE: what is this "hair pin" thing attached to anchor bolts?
Regards
Andy Machon
RE: what is this "hair pin" thing attached to anchor bolts?
RE: what is this "hair pin" thing attached to anchor bolts?
RE: what is this "hair pin" thing attached to anchor bolts?
However, many times the foundation pedestals and footings cannot be designed economically to resist this lateral force. If the footing is sunk deep for frost, or the base of the column is raised above the surrounding grade the high eccentricity would cause the footing to grow substantially. In these situations, engineers use the hairpin bars to transfer the lateral force back into the interior floor slab, which in this case should be reinforced.
Two problems with doing this: 1. The slab may be altered, cut, or slotted for drains in the future which could compromise the integrity of the system. 2. The slab-on-grade could settle, causing cracking and spalling around the interface between the foundation and the slab. You could wrap the rebar, in the slab adjacent to the foundation, with a foam insulation for about 12 inches of length. This would allow flex in the rebar if movement did occur.
RE: what is this "hair pin" thing attached to anchor bolts?
The reinforcing steel industry refers to supplemental cross ties as 'hairpins' which I think you are now familiar with based on the foregoing discussion.
There is another form of 'hairpin' used in my industry (guyed and self-supporting tower construction). The term commonly refers to a solid steel bar bent in the shape of a U-bolt and threaded just like a U-bolt. These tensioning devices are generally used for anchoring very large diameter guy wires. It is used for applying pre-stress to guy wires and forms part of the guy wire assembly. It attaches to the anchor steel by means of a shear pin. A good description of this type of 'hairpin' is available in the USSteel Wire Rope Catalog.
RE: what is this "hair pin" thing attached to anchor bolts?
RE: what is this "hair pin" thing attached to anchor bolts?
Your question interests me too. But new visitors to this thread may miss your question and may end up answering the question at the top. You understand THE TIME THING
Lets wait. If we dont get response, lets start a new thread so that everyone can see your question
Good luck
RE: what is this "hair pin" thing attached to anchor bolts?
I had the same question a little while back. I got hairpin design information from Butler Manufacturing Co. (Butler Buildings) while we were planning on specifying their product for our project. I'm not sure if I'm at liberty to copy this information and give to you, so I will give you the reference that the information came from: "Foundation Design & Construction Manual", Butler Manufacturing Co., Computerized Structural Design, Inc. Hope this helps.
RE: what is this "hair pin" thing attached to anchor bolts?
Is Butler at http://www.butlermfg.com?
RE: what is this "hair pin" thing attached to anchor bolts?
RE: what is this "hair pin" thing attached to anchor bolts?
I hope this is not too late. The "Hairpins" are used to transfer the lateral forces into the slab to prevent the lateral thrust. The hairpins are nothing but the reinforcing bars that are bent at 30 degree with specified lengths and size to resist the horizontal loads. It is not always necessary to use hairpins sometimes the force can be taken care of by adding reinforing bars from one column base to another column base directly across from it.
Gita (Structural)
RE: what is this "hair pin" thing attached to anchor bolts?
Rod
RE: what is this "hair pin" thing attached to anchor bolts?
Then, you have to make sure the reinforcing within the slab is enough to carry the tension force to the opposite set of hairpins.
Personally, I don't use hairpins. I use bars hooked into the pier, embedded in a concrete strip below the slab, with ties at splices. To me, this is easier to rationalize and anyone digging in the future will notice they've encountered something worth thinking about (hopefully).
JPRiley
RE: what is this "hair pin" thing attached to anchor bolts?
RE: what is this "hair pin" thing attached to anchor bolts?
1-Your minimum depth is the frost line.
2-Your design depth is whatever comes from your analysis of mat foundation
3-If frost line governs then you can do some economy by keeping your slab thickness minimum and provide a thickened slab along the perimeter only.
4-You can do more economy by thickening the slab only under columns as required by analysis and cut down depth between columns. This is not difficult in practice and we would usually cast concrete twice, first for the thickened column areas and then in between columns.
My five cents worth boss
respects
ijr
RE: what is this "hair pin" thing attached to anchor bolts?