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Deflection limit for un-insulated butt glazed glass

Deflection limit for un-insulated butt glazed glass

(OP)
I have not been able to find any limit for the deflection of butt glazing in the US codes for uninsulated glass. It is frequently specified as L/100 which is a code limit in Europe. The Australian Standard specifies L/60.

Has anyone used L/60 or even less in the US?

RE: Deflection limit for un-insulated butt glazed glass

glass99:

a little late to the party here but saw you in another thread, interesting to see another guy on here in the glass biz.

Rule of thumb i've used has been l/60, sometimes less - from the canadian code, NBCC, i kind of cross interpretted what they said about floor deflection: it should be no less than l/180,270,360, or a reasonable value to address occupant comfort.

On some big spans with glass you can get over 2" of deflection and still be in the safe range for stress - pretty sure the folks in the building would be spooked though! I get to play much more of this cross-interpretation game in Canada as our codes for glass encompasses almost nothing. reference alot of US code too.

RE: Deflection limit for un-insulated butt glazed glass

(OP)
Thanks NorthCivil - Now knowing you are a glass guy it explains why your recent comments in the business forum were on point.

Do the Canadian codes actually give specific guidance on this, or is a matter of judgement? Judgement is such a wildly variable thing on this topic. Reviewing engineers get nutty conservative about this, and it drives me crazy.
- Cable walls are typically designed for L/30 to L/50, which on a 100 ft span is ~3ft of deflection. We just finished the World Trade Center cable walls with deflection at that scale. The Kimmell Center cable wall in Philly which we did at my old firm moves by >1m. The famous Kempinski hotel in Munich moves by a similar amount.
- Regular butt glazed storefronts which are not engineered are super common in NYC being 1/2" FT with spans of ~12 ft, and move when you push them with your pinky finger, and they survive hurricanes.

And no, occupants don't notice crazy movement for either of these. If only someone would write down a number! I have been chatting with the president of the ASTM committee for structural glass. I want to set the limit at L/30.


RE: Deflection limit for un-insulated butt glazed glass

glass99

again, late... Been much too busy to check the site lately.

The Canadian code really has almost nothing - for the matter of deflection, it does defer the matter to judgement. Our entire code for use of glass in structures is about 20 pages, including figures, as well as covering content in both English and French, written in the 80's before FEA was a thing. I hardly pick it up; it has a couple nice tidbits about tolerance ranges for fabrication sizes (I'll analyze a 6mm sheet at a size of 5.56mm).

If I need to look at holes, I reference American; glass fin walls, i reference Australian, etc. I could forward you some of the Canadian stuff if you would like. L/30 is pretty reasonable in a lot of situations. Usually I'll shoot for less than 1" as my own rule. Handrails are usually where deflection can be a pain.

I'm not sure if there is a PM feature in this site but I wouldn't mind getting in touch via email to discuss technical topics more in depth without loss of anonymity. let me know... take a look at my last post in the finite element forum, I'm having some troubles these days.

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