Adhesive anchors and torque

[Bammer25]

I had a question come up that I am embarrassed to be confused on. We are using hilti hy200 anchor system which asks for a pre torque of 100 ft lbs. I know this is a clamping force to clamp down the attachment.

The question I am struggling to answer is “how can you say that applied torque and resulting tension in the bolt and therefore adhesive/epoxy is not going into the concrete?”

I know the load is resisted by the bond between the epoxy and the concrete, but is this value already taken into account in the load tables? I know that it just be. Just struggling with how to answer this

 

[phamENG]

It's how they tested it. The anchors used in testing to produce the load tables are installed using the installation procedures they publish and we require contractors to follow in the field. So, within a reasonable margin, the anchor in your structure will have the same initial conditions prior to loading that the ones did that went through the test rig. If those could handle 5kips of uplift with that installation torque applied, yours will, too.

 

[Bammer25]

Thanks. So the quick answer is that those loads are real. (On the concrete and the steel) and already accounted for in the allowable load tables

 

[phamENG]

Let's back up a second. Are you specing the Hilti HIT-Z rods to go with it? Otherwise, there is no minimum installation torque for adhesive anchors. The HIT-Z rod has a special shape that allows it to act as a torque controlled anchor in a similar fashion to mechanical anchors. It means the contractor doesn't have to clean the holes.

 

[r13]

I think this is a test load to ensure the full contact of the epoxy to the concrete, since cleaning of the hole is not required.

 

[STrctPono]

Bammer, piggybacking off of what phamENG said, look at first table for HIT-Z anchors. You will notice that there is a "t inst" which is the installation torque recommended.

The second table shows a HIT-HAS threaded rod. You will notice that this calls for a "t max" which is the maximum allowed torque. These are different from each other as the first one is the recommended installation torque and the second one is the maximum allowed tightening torque at installation.

Yes, HILTI accounts for these torques and corresponding tension loads when they provide their design values. For some of HILTI's systems you can also reduce your edge distance if you reduce the installation torque. This is all summarized in the Manufacturer's Printed Installation Instructions (MPII).