Stone cladding kerf support

[cw1info]

We have a problem with stone cracking the front leg of the kerf.
It has a bottom continous kerf support angle with an upturned leg in the front and anchored at the ends.

My boss has a theory that clearance within the kerf is too small. As the dead load of the stone is applied, the center of the angle will twist in relation to the fastened ends. When the twisting occurs, the upturned leg will stress the outer leg of the kerf.

It sounds good, but the calcs say otherwise.

Is it valid to run a deflection analysis disregarding the primary upturned leg of the angle since the cantilevered point is that intersection?

Thanks

 

[youngstructural]

Just to be clear, you're saying that thee shelf angle is cracking? As in one of the two angle legs has developed a crack? I think you mean that the stone supported by the kerf is cracking, but I'm really not sure from your post...

If the stone is cracking, this is often due to environmental influences lowering the allowable stress of the stone. So in effect the environment is erroding your material strength. This is an all too common problem now. I would not be suprised that your numbers don't match what you are observing if this is the problem.

Please post more detail, perhaps someone can shed more light on the problem...

Cheers,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[apsix]

For kerf I found this definition; KERF: A slot into the edge of stone with saw blade for insertion of anchors.

I assume in your case you have a continuous slot in the bottom edge in which the vertical leg of the angle is inserted.

As you probably know the angle will twist if not loaded on the shear centre (which is at the intersection of the 2 legs) so your boss's theory sounds plausible.

"Is it valid to run a deflection analysis disregarding the primary upturned leg of the angle since the cantilevered point is that intersection?";
Probably not, as explained above, but I don't understand the second half of the question.

 

[DaveAtkins]

Was silicone used in the kerf, as is proper? Silicone would allow for that vertical leg at the toe of the angle to flex without stressing the stone. If mortar was used, it would not allow this.

Could there be water in the kerf? Water expands when it freezes, and would crack the stone.

DaveAtkins

 

[cw1info]

To clarify, the stone is cracking near the kerf cut or continuous slot at the bottom of the stone. The support piece is an u-shaped piece with unequal legs. The shorter leg is in the continuous slot.

Our theory is the stone deadload may not be in the correct position along the length of the support piece.

Thanks for the help.
Cw1pmmi