Guy Anchor Detail

[sekwahrovert]

I have designed a guy anchor (reinforced concrete block) and some questions have been raised about the detail I provided. Please see attached and provide any feedback if anything jumps out at you. Thanks in advance.

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1490112234/tips/Guy_Anchor_Detail_dqidqi.pdf[/url]

 

[Nor Cal SE]

Thanks for sharing, Sekwahrovert. Without knowing the load demand on the guy anchor, here are a few thoughts:

1) I would be really specific about the specifications on the guy wire, preferably with an ASTM callout, plus the diameter, and it should have some short of head or j-bolt type of configuration at the low end to provide pullout resistance. I would also specify the minimum concrete embedment. I realize some of this you might have already specified in written specs or elsewhere.
2) You will need to check the anchorage capacity per ACI 318, if you haven't already done so.
3) Based on my own experience, I know the contractor might have a very difficult time getting that cube of reinforcing put together, due to all the intermediate layers. I would recommend putting the mats of each-way reinforcing only on the outer faces of the footing (therefore, 6 total mats of each-way reinforcing, 1 on each face). You can upsize the bars as needed to meet the ACI 318 min-reinforcing requirements. With this large block I'm guessing you don't need the reinforcing to act as any tension resistance. Your contractor will definitely thank you.

 

[MotorCity]

Most contractors and rod busters probably won't know what you mean by "line of force". I would provide hard dimensions (or relative dimensions) of exactly where you expect the guy anchor to be located within the block. I think it will also be a challenge to thread the guy anchor through several layers of rebar and hold it precisely at the angle you have shown (actually, where is the angle shown?) with the end floating in the middle of the block, holding it taught, while the concrete is poured and cures. You may want to consider a detail of what the end of the guy anchor looks like and some mechanism to hold it in place, maybe wrap it around a rebar?

 

[cvg]

typically you would have a j-bar or steel plate embedded in the deadman. You would have a connection point on the end of that to connect a cable or rod and turnbuckle system in order to tension the guy properly.

 

[Lomarandil]

You can also embed a length of PS strand in the deadman concrete to act as your guy anchor point (then add shackles/turnbuckles as needed). For most deadman sizes, you can get plenty of embedment for development length.

Agreed about placing the anchorage aligning with the "line of force" -- difficult to construct. Do you really need that for the deadman to calc out globally? As a contractor, I'd probably rather pull out a 5x5 deadman out of my yard then worry about making this special 4x4. Or if a 4x4 with an anchor at the top center would work, so much the better.

I've never thought about it, but I also agree that the layers of internal reinforcing seem unlikely (to be required, constructed properly, etc).

----
The name is a long story -- just call me Lo.

 

[chicopee]

As you seem to be concerned with the line of force in line with the block center which is fine, wouldn't it be more advantageous to have a slot within the block so that an anchor rod with a pivoting end is attached to a pin positioned at the center of the block. When all connections are made and tightened between the dead man and the guyed structure, the guyed system is aligned and then the slot can be grouted for weather protection.