Glass with point supports 1

[dcceecy]

we are working a bus shelter. the roof of the shetler is glass hung from steel joists. the glass panel is about 4.33'x6.67'. The panel has four point support from the joist.
Now have to design the galss and the connection. I never do such design before.

any suggestions

 

[MiketheEngineer]

Various glass mfgs have tech manuals. I beleive there are a couple of tables in the IBC also.

Google might be your best friend here.

 

[msquared48]

I would hope that it was Plexiglass or Lexan, but, then agaqin, you mentioned that an Architect was involved....

Oh well...

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[MiketheEngineer]

And bullet proof

 

[Ron]

Don't hang glass over people...not a good idea.

 

[Lion06]

When I do glass design I use ASTM E-1300. There are a lot of tables in there that you can use if you're using one of there specific cases and you're loading and spans are within the range of the tables.

They also give values to use for other conditions. For point supported glass panels I typically do a FEM of a plate element to get the maximum bending stress and compare that to the values out of E-1300. I haven't used it in a little while, but I think the tempered glass value is like 10.2 ksi in bending.

Annealed has the lowest values, heat strengthened is next up the list and tempered has the best values. I would never hang anything overhead that was anything but tempered.

Finally, if you use laminated glass take note of the low percentage of composite action for loads longer than 3 seconds. E-1300 is geared toward generic interlayers (which is the thin film between laminations in laminated glass) which has poor creep characteristics. DuPont has an interlayer (called Sentry Glass Plus) which has better creep characteristics and gets higher composite action in laminated glass.

 

[dcceecy]

I find a
Glass Informational Bulletin GANA LD 03-0505
for Point Supported Glass

It says
"One of the more complex concepts for structural engineers to grasp when designing structural glass is that glass, as opposed to steel or another metal, does not always fracture at the point of maximum stress"
It also suggests to use tested systems
so now I am looking for some glass manufacture who made such systems

 

[RacingAZ]

Ron, I'll second that. Bad design from the architect though I'm sure it will look cool.

This is a lawsuit waiting to happen. Public structures like a bus shelter sees more act of vandalism than others. What's stopping a bunch of teenagers from hanging from that glass?