What is the span of a pane if the pane is not rectangluar?

[sebmaster]

Hi,

Given a maximum span for a pane of glass calculated from BS5516, I am wondering what happens when the pane is not rectangluar (e.g. it adjoins a gable) and the longest edge is larger than the max span?

For example,

Say you calculated the span to be 1m (two edge supported) and the top edge had a length of 1.2m while the bottom edge was 0.7m.

How would you determine if that pane was satisfactory?
I.e. Take the longest edge? The average of the two? Calculate the span halfway up the pane?

 

[theoldun]

Are you by chance trying to work out thickness of glass required.
oldun

 

[sebmaster]

Hi theoldun,

Yes I am , or more specifically, I have determined that 6mm thick glass can span 1.1m with my loading. This is OK for almost all of the panels, but a couple that adjoin the gable exceed this at the top.

I just wanted to check if there was a standard way to calculate the 'equivalent span' for an odd shaped pane, but if not i'll just go for 8mm which exceeds my requirements.

 

[Ossy]

Well, is it really just one-way spanning or is it supported on four edges? I know nothing about glass but using concrete or steel there would be ways of analysing it to allow for 'odd' shapes, using yield lines for example. Not sure how you would model glass though as it wouldn't behave elastically or plastically (I assume but may be wrong)! Not familiar with the code you mention, but is there not a section (or appendix) that mentions something like this?

I suspect going for thicker glass would be the easy route. You might be able to prove it for 6mm but is the cost difference worth the hassle?

 

[sebmaster]

Hi Ossy,

Its supported at two edges; the glass does behave somewhat more plastically than I would have thought (the limiting factor in my span is the deflection! )

I will do a search of the standard but I agree; I posted just as a quick check and the lack of an absolute answer is the answer itself, i'll go for 8mm. I haven't checked the cost yet but that is always going to come second to it not collapsing in on my head when it snows!