anchor bolts

[broncosfan]

Is it better to provide anchor bolts with a hook or a tack welded nut for anchorage. Literature seems to recommend a nut. Contractor's seem to like the nut better as well.

 

[bjb]

The nut method is recommended if you have a calculated tension force in the anchor bolt. I have seen video of a test where a hooked bolt straightened and then pulled right out of the concrete. We never use hooked bolts for any of our anchor bolts, even if there is no tension force in the bolt.

 

[JStephen]

Per the current ACI-318, the allowable load for heavy nuts (or bolt heads or welded washer plates) is a lot higher than for hooks. If a bolt is oversized for the application, a bend may be acceptable.

 

[Dinosaur]

I did some recent work on anchor bolts for my organization and found that according to Modern Steel Construction magazine anchor rods should be specified as ASTM F1554 material. Reading this ASTM, I learned that they think hooked anchor rods should not be used in application inducing tension on the rod. It could be for the reason cited by bjb that hooks may try to straighten out. Good luck.

 

[EngineerofSteel]

Broncos fan,

Check with the contractor, or with local suppliers. In this area, contractors like to use pre-welded anchor bolt assemblies. Two anchors (e.g. (2) 5/8ths bolts) will be joined by a horizontal bar.

The horizontal bar increases the pull-out cone.

For the contractor, it holds the anchors rigidly in place during concrete pouring.

You will be limited somewhat on anchor bolt spacing in your design. These typically come 12" cc, 18" cc, etc.

-DD

 

[XBLEE]

We use anchor bolts with a washer and nut on the embedded end. Instead of tack welding we mar the threads so the nuts wont back off. Hope that helps.