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Re: Cantera Stone Attachment to Steel Frame Arch

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Hi Denise,
 
Please see below for my response.
 
> I need to know if anyone has successfullly attached 250# pieces of pinon cantera stone to a tube steel
> moment frame in the shape of an arch. 
 
I don't have any experience with this particular stone, but have on many occasions hung varying kinds of Granite and Marble stone.
 
> The fabricator has suggested using expansion anchors and steel L-angles welded to the tube steel. 
 
You "really!" do not want to fasten the stone directly to structural steel.  The preferred method is to anchor the stone to a light weight tube steel frame and fasten the tube steel frame to the structural steel.
 
> I think the expansion anchors will blow out the stone if placed too close to the edge. 
 
You "really!" do not want to use expansion anchors, period.  Contact the manufacturer of the stone and tell them you need dovetails cut in back of the stone.  They will also be able to hook you up with some dovetail anchors that you can attach to the tube steel frame.  Someone needs to be paid to coordinate all this.  Is this in your scope of services?

> Does anyone have any info on the strength of cantera stone or an acceptable
> edge distance?
 
Again you need to contact the manufacturer and ask if they can provide you with a test report "C880-96",  ASTM C880 Standard Test Method for Flexural Strength of Dimensional Stone.  You need this report to efficiently design the anchor pattern.  The flexural strength of stones I have worked with vary between 1,000 psi and 1,500 psi.
 
> The stone looks porous and  has pockets of volcanic rock and
> minerals.  For this reason, I think epoxy adhesive would be more reliable.
 
You can certainly use epoxy, but I think it would be prudent to backup the epoxy design with values derived from actual tests of a full scale connection assembly.  Precast fabricators do this kind of work all the time.  They have taken the time and trouble to complete "all" the steps above to assure themselves their designs will perform.
 
The thought of a 250# piece of granite falling to ground carries with it substantial liability.  Is your laibility insurance paid up?
 
Go visit a precaster and see if they will share with you any design concepts.  Many have developed proprietary methods for attaching stone.
 
Good Luck,
 
Keith De Lapp