Anchor Bolts on Granite Wall

[mgt89]

Hi all,

I'm designing a steel deck for a floor, with a group of simple supported beams, that will be connected at each end to a masonry wall made of granite (figure below). I´m trying to determine the number of anchor bolts that it will be required on the connection to the wall, but I'm having some trouble figuring out the design resistance of the anchor when fixed to granite.

I´m using Hilti' product HIT HY270 + HIT V(5.8) M12, but on their technical tables, they do not show design resistance for granite. The force that I will need to transmit is around 15 kN.

Thank you for the help.

 

[hokie66]

No photo attached.

 

[mgt89]

Added to first post

 

[chicopee]

See if you can get information from stone cutting operators involved in cutting granite into slabs as they may be able to guide you in the right direction.

 

[mgt89]

Hi,

There´s no cutting granite operator. This is a rehabilitation and they will just anchor the beams to the wall, and execute the floor with standard materials (osb, thermal insulation etc)

 

[thaidavid40]

Try contacting the Elberton Granite Association for some advice and guidance. They can be found on the internet here: Link
Dave

Thaidavid

 

[bridgebuster]

Two years ago on a project we used Hilti KWIK-HUS (screw anchor) to attach supports for temporary stair towers attached to granite bridge piers. We pull tested them to ensure they would work, and they did. You can call Hilti to see if they have info or if a field rep could perform some pullout tests.

On a recent project, we're using dowels grouted somewhat horizontally into rocked, mostly gneiss, to provide stability for concrete walls. The rep from Powers came out and did some pull tests for us. I think Powers has some info for stone; I'll have to check on Monday when I get back to the salt mine.

 

[JoelTXCive]

I think all the above suggestions are good and worth pursuing.

Am i understanding correctly that you will have a beam mounting to the granite wall with some sort of plate anchored to the stone. Load will be transferred via shear in the bolts?

How thick is the granite wall? I'm thinking you are going to have to do some surface prep involving grinding and cutting just to get a good flat working surface to mount what ever you are going to mount. If so, could a little shelf or pocket be cut in so that you are transferring load via bearing and the shear in the bolts? No easy way to do the math on that but it would build some redundancy in the connection since you might not have perfect information on the anchor's capacity in the stone.

Also, if you have the space available; maybe your mounting plate can be enlarged so that you can get additional anchors in the stone?

 

[mgt89]

HI all,

Thank you for the answers. Below is a sketch of the solution that I´m currently pursuing, with cold rolled beams C250x70x2.5 spaced of 625mm.

@JoelTXCive the wall is 400mm thick. I don't think it will be possible to create a "shelf" where the beam would be supported. The shear must be transferred only through anchor bolts, unfortunately.

 

[XR250]

It would likely be really conservative to use numbers for masonry. Granite is pretty tough stuff.

 

[MacGruber22]

Not sure where you are located, but Cathedral Stone Products (

http://www.cathedralstone.com/)

are experts at everything masonry, stone, clay, new and old. They can make grouts customized for the chemical composition of the existing substrate. This not only allows an optimized bond but also allows the grout to be thermally compatible with the old stuff. Otherwise, Powers or Hilti readily provide load testing in place[color. We have them do it regularly for exposed aggregate panels on old parking garages. They capacities are always surprisingly better than an idealized calculation with interestingly shallow embedments.

Masonry solutions are also experts similar to Cathedral.

http://www.masonrysolutions.com/

-Mac

 

[OldBldgGuy]

As XR250 says, masonry numbers are going to be very conservative for granite when looking at the capacities of individual fasteners, as long as you regard edge distances on individual stones. I must say I wouldn't want to drive self-tapping type fasteners into granite, and adhesive anchors are for sure going to be limited by the anchor capacity if the edge distances are observed. Even if you have the odd anchor hitting a mortar joint, that's a pretty good looking wall & I wouldn't be losing a lot of sleep over it.