Anchor Bolts To Granite 1

[EngineeringEric]

So I have a unique project attaching to a Block of Granite. I do not really need to resist any substantial tension or shear loads as the objects are all self stable in terms of gravity and overturning, however they do need to be anchored. Exposure is exterior but not corrosive or sea.

I am looking at stainless steel anchors with a diameter of 3/4"-5/8". Do any of you know of a good product for Granite or similar stones? I know there are wedge anchors for stone but part of me wants to stay away from things that may pop or induce forces which may break a natural crack.

Maybe epoxy sleeves, taper bolts(?), Mechanical screws (titen HD).

Edit:
So the write up may not be 100% Clear... This is a small steel installation that will be supported by an imported granite stone 'boulder'. So no concrete backup or slab on top.

 

[MotorCity]

You can use anchors that are used for cast in place concrete or post installed anchors and they will have SOME capacity. The question is how do you quantify that capacity since anchors are geared for concrete or cmu. Seems to me that stone would be as brittle or more brittle than concrete, so the tendency for the granite to pop or crack would still exist regardless of the anchor type. To go one step further, how would you calculate the various limit states for the granite? I am sure its not the first time anchors have been installed in granite, but I may start by looking at the fascade engineering industry.

 

[atrizzy]

Usually a geotechnical engineer will be able to provide you with some basic withdrawal resistance values for rebar drilled and grouted into bedrock. Use the withdrawal resistance values to calculate interface shear resistance and that should be all you need, if I understand your writeup correctly.

This is assuming that you're planning to pour concrete on top of the granite.

 

[bridgebuster]

The attached may be of some help. As MotorCity said you can use the same anchors as you would for concrete. I've done a few fancy retaining wall projects recently, which had stone coping. In designing the anchor we assume unreinforced concrete. Also, two years ago I did a project for a contract. One element was a 90' tall temporary stair anchored to a stone bridge pier. They used Hilti KWIK-HUS bolts to secure the lateral bracing. They pull tested a few and the numbers came up good.

 

[EngineeringEric]

Thank you all. And this just in" we have 3" edge distances!

 

[JLNJ]

You might try the people at Williams Form. They normally deal with BIG rock anchors, but they might have some insight.

3" edge distance doesn't seem like enough.

 

[dik]

Can you use threaded rod/anchors with Hilti Hit-Hy 70?

Dik

 

[cvg]

Williams has a Polyester Resin Rock Anchor for a 3/4 inch diameter bar

http://www.williamsform.com/Ground_Anchors/Polyester_Resin_Rock_Anchors/polyester_resin_anchors.html

 

[OldBldgGuy]

Sika Anchorfix (look at their website for the specific one) and SS threaded rod. I use it for sculpture installations frequently in exactly the scenario you are describing.

 

[JedClampett]

Why don't you put one in an inconspicuous spot and test it?

 

[thaidavid40]

I feel you pain, as regards some practical design advice. I recently had to work on a project where the architect wanted a composite granite slab mantle to "float" above an outdoor fire pit. We ended up with a concealed steel frame supporting an underhung mantle. I inquired of the granite supply folks - who have done a lot of non-standard projects over the years - what advice they might give me on the attachment of the hidden support studs that would secure the slab under the framing. They had very little advice that they could offer me beyond the most basic of generalities. I finally came up with a system that I could theoretically trust, and gave it to them as a freebie. For now, the system is working properly. I just hope that lasts!
Dave

Thaidavid

 

[dik]

Hilti also has a 'hole roughener' if the cores are drilled. This provides a surface that is less smooth. I also like to use Hit-Z anchors due to the 'wedge' shape of the bonded part. Any movement causes a compression on the epoxy against the hole.

Dik