Wedge Anchor Question

[floodrod]

So I need to install some guy wires into a concrete block with wedge anchors.. They are rated at 10,000+ pounds tension. Obviously I want the best attachment.

Would it be better to install them in the side of the concrete block instead of the top surface? See pic..



I know they are designed to be mounted a "B" shows. But would mounting them on the side as "A" shows be beneficial?

My initial hunch is side mounting "A" might cause cracks in the crete easier. But if it doesn't, it may provide greater attachment point.

Any feedback?

 

[Raspy]

If you are worried about the strength of the bolts, go to a larger size. I'd say the side mount might take a sustained load better if you are near the limit. Also you can, after blowing out the holes, put in some construction epoxy and then drive in the bolts and tighten them. Make your attachment plate such that it doesn't try to bend the bolt under load. Remember, when used to hold down wall plates, or bolt down machinery, the bolts are mostly under a shear load and not tension.

 

[oosik]

Actually, what you end up with will depend upon the strength of the concrete, the strength of the bolt and method of attachment. As Raspy indicates - if you go with "A" - I would go one bolt size larger. This would help prevent the bolt from bending.

 

[JimRB]

The only time I used wedge anchors for a tower I mounted an anchor plate to the concrete and the guy wires were attached to the anchor plate. The concrete was substantial, not a concrete block. Attaching something to the end of threaded shank of a wedge anchor is probably outside of design specs of a wedge anchor. Are these concrete blocks actually concrete pads X feet thick, X feet square weighing X tons? How tall is the tower the guy wires are going to? That tower we installed was done after an engineer designed the attachments and tower pad.

 

[s219]

I don't think case "B" is consistent with the design of wedge anchors. As others have noted, they are meant to handle side loads and only have much lower resistance to pullout (this is true of one-way fasteners in general -- if pullout loads are the priority, bolts with nuts and backing washers should be used, or in the context of anchors, something with a solid grabbing point below, like a J hook or plate).

So I'd choose approach "A" hands down, as long as the concrete was properly reinforced and had some re-bar to handle any tension loads.

Have you tried googling for any specs on the pullout resistance of the wedge anchors that would be used for "B" ? You could probably do a simple calculation to see how that number compares to the tension loading that you'd apply to the concrete in approach "A". If the pullout resistance from "B" exceeds the cracking potential from "A", you'd have your answer right there....

 

[RedNeckRacin]

The problem I see is that your anchors might not be rated for side loads. I know Crosby fasteners has very specific angles that certain bolts are rated for. A bolt in arrangement b is almost a pure tension load which a thin member takes well, arrangement a is a different loading type. Usually bolts or eyelets for this situation have a shoulder to support the shank. What type of load and fastener are you using.

 

[EddieWalker]

Since you are asking about anchor bolts, is it safe to assume that the concrete is already there? How thick is the concrete and how close to the surface are you planning to mount the anchor bolt? How tall is the structure?

If the concrete isn't thick enough, or deep enough, I would strongly suggest digging a new hole and setting a eye bolt in it while the concrete is wet. I like to add washers to the threaded end of the bolt and use two nuts to hold them in place for something like this. On my zip line I used a length of flat steel with a bunch of holes in it that I bent at the ends and used two nuts to hole it to the eye bolt. For me, this would be the only way I could be positive that it wont fail.

Eddie

 

[SPIKER]

Like others suggest, the A method would be better for a tension load. I would like to say that there are methods of anchoring without concrete that are far superior if you have not put in the pads yet. There are auger systems and (forget the proper name) where a crossed up auger/anchors are nearly impossible to remove by pulling in their designed angular direction..

Mark

 

[CDN Farm Boy]

Without factoring in the strength of the concrete, any decent concrete anchor will be rated for both shear and tension load. Assuming a non-thru anchor, shear ratings are always higher for post-pour anchor installation.

Having used hundreds of both wedge and epoxy anchors, it's pointless to try to epoxy a wedge anchor in unless you drilled too big. The epoxy will set before you can tighten the anchor and might as well be threaded rod at that point.

If you do use epoxy, don't forget to blow the dust out of the hole first

 

[greenboot]

You say it is rated at 10,000 lbs. Is that the cable or the anchor? That is a tremendous load for any wedge anchor, especially in pullout as shown in B. For that much force, I think you need to cast the anchor in place or use a fitting with multiple wedge anchors.
Tom