Bearing stress for tempered glass at bolt

[StrucutreDr]

Hi,
I want to know the allowable bearing stress for glass at location of bolt.
The location is the splice location for the glass fin which has bolted connection arrangement.
ASTM E1300 specified edge stresses for different types of glass in (TABLE X9.1 Allowable Edge Stress).
Can these values (73MPa for tempered glass) be used to check glass bearing stress at bolt location.
Is load duration factor of table X6.1 required to be multiplied to values in table X9.1.
Thanks,

 

[klaus.]

up to now there is no such thing as bearing stress for glass at holes
you need to do a 3-D FE Model and/or do testings on real size samples




best regards
Klaus

 

[klaus.]

The allowable glass stress is depending on the load duration time
short time ( wind ) ==> higher allowable stress
long time ( dead load) ==> much lower allowable stress

the 73 MPa are for short duration only ( 3 second load)
for long term load the value is about 50 Mpa

this is true for vertical glass ( facade)
if the glass is horizontal ( like roof) then the values are lower


best regards
Klaus

 

[dhengr]

StructureDr:
I don’t have the ASTM Std. in hand, but I don’t think you should ever have a glass edge bearing directly on a bolt, or directly on any steel frame either. There should always be some rubber bearing blocks or rubber grommets in the picture or you will very likely cause glass cracking. We can’t see your details or exactly what you are looking at from here, but concentrated edge loads and any kind of glass just don’t go well together.

 

[NorthCivil]

This topic hasn't been refined as a science quite yet, much less been put into code. lots of good research papers coming out of the university of Lund about the topic - have a google.

That's all you'll have to go by, together with a bit of engineering judgement.

 

[klaus.]

Yes of course there should be no direct contact between glass and steel(bolt) but still there is bearing stress of course
between Bolt an glass is usually aluminium and/or grounding ore something similar
The new German glass code gives advice on point supported glass... and lots of research papers somewhere in the internet



best regards
Klaus

 

[StrucutreDr]

Yes there has to be a bush between glass and the bolt.
But still what should be the allowable stress for the glass considering the bush size?

 

[klaus.]

to my knowledge this is still under academic investigation or research

if you do stress calculation ( using FEM ) you need to use the reduced allowable stress because the hole is considered the same as edge
and edge stress is less than surface stress

If you have a bigger project it might be better to do testing on real size samples



best regards
Klaus