3/4" thick glass balaster design

[Berniedog]

When we design cantilevered fully temperated, glass railing (3'-6" high), the baluster is typically 4'-0" wide. Applying a 200# point load at one corner, we assume a 30 degree angle for load distribution. This allows a 2'-0" width of glass at the bottom to resist the horizontal 200# load.

What do other Engineers do?

Our client does not want to use 3/4" thick glass but our calculations indicate that the 1/2" thick glass will not work.

We are using a FS of 4 and Fy=24 ksi.

 

[BAretired]

I don't know what other engineers do, but I would be reluctant to make that assumption. Localized stress at the bottom corner of the panel are likely to be higher than average stress with the possibility of initiating a crack.

The properties of tempered glass are variable depending on the tempering process. 24 ksi is not a yield stress...it is an ultimate stress according to several references.

I would not use an all glass baluster without doing a lot more research. Maybe steel or aluminum frame with glass suspended between.

BA

 

[Berniedog]

The 24 ksi is the modulus of Rupture not Fy. Glass railing is commonly used.

 

[csd72]

Do you not have a steel tube across the top?

If so then this would spread the load between 2 edges.

 

[BAretired]

That does not make it right. The strength of the material is not known or, if it is, is not being clearly presented in the literature. The following links indicate doubt about the strength of tempered glass. In the second link, it is stated that tempered glass is 40% weaker when oriented vertically than horizontally...not an intuitive result.

http://www.glassfiles.com/discussions/message.php?id=1159

http://www.icf11.com/proceeding/EXTENDED/4453.pdf

BA