Anchor Capacity in Clay Tile Wall

[Mike Mike]

I would like to anchor a steel plate to face of hollow clay tile unit with toggle bolts, collapsible screw sockets, self-clinching nails, epoxy screens, umbrella inserts, etc. as shown in the following images. One important check is face shell flexural tensile stress. Does anyone have a method of estimating the modulus of rupture? TMS 402-13 table 8.2.4.2 lists the wall assembly at around 20 psi, but these values are typically controlled by the interface between mortar and unit, so I would expect unit capacities to be higher than assembly capacities. ASTM C67 "Standard Test Methods for Sampling and Testing Brick and Structural Clay Tile" does specify test methods for modulus of rupture, but I have an ASTM C67 test report from National Brick Research Center on Elgin Butler clay tile, and only compressive strength is listed in the report.

In a related post, thread507-275569 Ron said "About the only way to get any capacity in structural clay tile is to use toggle bolts. That's slow, expensive and a pain in the a$$. The tiles are often brittle or extremely soft and friable...not predictable. When you get roofers or others trying to drill through them to fasten anything, the result is not pretty."

Another option would be to remove 1 course of existing tile from top of wall and fasten channels to underside of slab like a typical non-bearing wall brace, but the team would like to avoid this if possible.

 

[masonrygeek]

I would check with retrofit anchor manufacturers such as Cintec or Helifix. They might have some anchors that can work with structural clay tile especially the sock-type anchors.

 

[NorthCivil]

I've been down the road of checking this, including site specific testing with the engineering team from hilti on a particular project.

long story short, unless those hollow blocks are fully grout filled, i wouldnt hang anything more than a picture off of those tiles.

pullout capacities are near nil with low reliability. shear strength, you may have some reliable strength in the realm of double digit newtons

 

[Mike Mike]

Thanks masonry geek, I don't see any values on Cintec's website. Do you have any contacts there?

 

[Mike Mike]

NorthCivil, was it in relation to Hilti HIT-SC screens? Do you recall what the dominant failure mechanisms were? I would only need around 30 pounds per anchor for this application, is that too far from nil?

Mason geek, Helifix Cementie is also a pretty bad ass product. I'm happy to know about these products even if they don't lead to me quantifying masonry units. You must be in Europe? I hear clay tile is more common in England. Here's a cool umbrella product in US: