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Re: Structual Design of Glass

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I can understand the site line issue about not wanting to interrupt the view with a top balustrade, but the UBC is fairly clear (I believe you have the same restrictions in the IBC), you have to have the continuous rail across the top of the glass balustrade (must engage at least 3 glass panels).  For the 1/2" thick glass to work as a balustrade, it typically takes about a 48" wide width of glass to resist the bending forces.  So if you end up with glass pieces less than 48" in width you will likely need a vertical stanchion member with a top rail between the stanchions, and the glass becomes an in-fill panel.
I am sure you will see plenty of places in various buildings around the country where they have not used the top continuous rail on the glass balustrade. The simple answer, It doesn't comply with the building code.  It got overlooked by the building department during plan check or they didn't understand the glass design requirements. The football stadium in Cleveland a few years back had a real problem with the same glass balustrade issue, and after installation (with no continuous top rail), there were glass failures and a lot of finger pointing. 
I have seen people use the hand rail as the continuous rail (using the hand rail brackets to secure the glass in place..often at the joint between the two pieces of glass... that will never work if actually loaded) below the top of the glass.
Most architects don't understand there are code restrictions, and the glass railing installers just do what they are told (after all they have been doing it this way for years). Some of the glass hardware providers understand the issues, and will warn the client of issues..but ultimately its left up to the designer and the building department. 
If you are doing this as a retrofit to an existing building, the continuous glass shoe base anchorage is typically based upon cast in place anchors in concrete and not expansion anchors, so that can be a problem with anchoring the shoe down for overturning/prying forces on the expansion anchors.  Some of the hardware manufacturers have done some testing, so you need to find out what data they have for base anchorages as a retrofit.  You will notice for new construction the steel embed plate is larger in width than the width of the glass shoe to help with overturning connection of the embed plate to concrete (shoe anchored to embed plate by machine screws in drilled and tapped holes).
Good Luck.
Michael Cochran SE SECB.
In a message dated 7/5/2006 1:21:59 P.M. Pacific Standard Time, ghodgson(--nospam--at) writes:

I'm having a little problem with a glass guard rail for a church
balcony.  They don't want a handrail as that would obstruct the line of

Does anybody have any experience designing glass or have any references
they can point me to?


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