Point supported glass

[blmce]

I need to design a glass guard rail and hand rail for a stair case. The glass will be tempered and will be attached to the side of the steel stair stringer with fasteners. These fasteners are to have washers embedded in the glass. The fasteners will be flat head with the flat head countersunk in the washer. That way the fastener does not extend out past the face of glass.

This connection looks a lot like the connections used on all glass walls where each glass lite is supported only at the four corners. I'm trying to find design data for this type of connection and I'm having trouble finding an answer.

Here are my questions:
1. What would be the maximum thickness allowable for the washer? I'm thinking this would depend on the thickness of glass required but I'm looking for a formula based on glass thickness or some type of general rule.
2. What would be the maximum bearing stress allowable on the glass at the washer? Or bearing force would be good to use too.

Thanks!

 

[SMF1964]

Wow. just some random thoughts:

The maximum washer thickness would be a function of the depth of the compression zone on the surface of the glass, wouldn't it? (Does it have to be glass and not some form of lucite or PMMA?) Is the washer going to be the loading point of contact between the fastener and the glass? If so, then you're probably going to need the actual stresses at this connection (bolt pre-load and applied load from someone hanging on the rail). If that exceeds the residual compressive stresses in your glass, then it falls down into many little pieces.