Table of Laminated Glass Thickness & Computation 1

[ralphi]

For say a frame that is sized 47 inches horizontal (about 1.2 meter) and 27 inches vertical (about 0.7 meter). What is the minimum thickness of laminated glass that can be used? Is there any table or how do you compute it? Can a 9mm laminated glass (composed of 2 pcs 4.5mm sandwiched with pvc) be strong enough?
Remember a laminated glass is composed of two glasses sandwiched with pvc (plastic) in middle so in case of breakages, the glass would still be held in place just like the front windshield of a car.
For flexure and shear. I think a laminated glass is effective for each side only.. but what happens when it is laminated with pvc (plastic) glued in the middle layer?

Thanks a lot!

 

[JAE]

"...be strong enough? "

Is this a window in an exterior wall? Interior wall? Does it serve some security purpose?

Things like that would help define the amount of pressure or force that the glass would need to resist.

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[ralphi]

It is fixed window for exterior wall in second floor. Pressure or force would typical wind and typical hurricane. I'd like to know some tables for minimum thickness for certain sizes of frames or glasses both for laminated and tempered glasses.

 

[KootK]

For wind loaded rectangular glass panels, ASTM E1300 has some charts that can be used for design. You'll need to consider a number of things:

- Is this an insulated glass unit with two panels separated by an air/gas gap such that load can shared between the panels across the gap? That is normally the case.

- For individual panels constructed of laminated glass sheets, horizontal shear transfer is imperfect. As such, you'll need to calculate effective panel thicknesses for strength and deflection. ASTM 1300 makes recommendations as does IStructE. Vertical, laminated glass in wind applications is usually treated as composite with neither glass layer considered sacrificial.

- If the window is located such that it is being used as a guard rail element, that will need to be considered. And it will likely impact decisions regarding tempering and load sharing.

- Based on the environment, thermal stresses may require some consideration.

- Glass design these days is a probabilistic affair governed by the presence and development of local flaws. As such, your design will include a factor accounting for the size of the glass panel will larger panels being effectively weaker.



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[ralphi]

I was referring to laminated glass with pvc plastic sandwiched in between (see file attached). Air or gas space would be more fragile.

I concluded the 9mm (23/64") is sufficient for 1.2mtr horizontal and 0.65mtr vertical frame, why? A car windshield has same size and it uses typical 6mm. And you can race your car to 100 mile per hour without the windshield breaking apart. Hence I think it is sufficient.

But then, is a Katrina hurricane stronger than a car moving at 100 mile per hour, anyone has computed it? Whatever, 9mm (23/64") would be sufficient. Who uses this size in windows?

 

[Compositepro]

Your glass is laminated with PVB not PVC.

"Polyvinyl butyral is a resin mostly used for applications that require strong binding, optical clarity, adhesion to many surfaces, toughness and flexibility."

 

[IRstuff]

How often does this window experience hurricanes, and is it expected to survive them all?

One major issue with hurricanes that does not occur with race cars is debris. Even a tiny pebble traveling at 150 mph would be expected to do noticeable damage. Additionally, race car windshields are heavily angled to the wind, while a typical window is not.

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[ralphi]

If you put a normal car with normal windshield (about 1/4" thick or 6mm) in the path of Hurricane Katrina or the strongest hurricane in existence. I wonder if the windshield would survive supposed it's not hit with a debris but just the wind. Well? Has anyone seen a car windshield that is damaged by just the force of wind/hurricane?

 

[KootK]

Consider the ways in which a windshield may be different from a building window:

1) aerodynamically sloped, as mentioned.

2) tempered.

3) curved in a way that augments strength via in plane membrane action, as mentioned.

4) possibly high grade interlayer giving improved stiffness for shear transfer.

5) Quite different quality control leading to differing statistical distribution of surface flaws.

Does your comparison have some rational merit? Absolutely, in my opinion. Should your comparison be considered an adequate basis for a final design? Absolutely not in my opinion.

But no, I have not encountered a windshield that was broken as a result of wind pressure alone.







I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[IRstuff]

Why do you think it won't survive?

Consider that race car windshields are exposed to more than the wind speed of a category 5 hurricane with no deleterious effects.

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[klaus.]

Well now a day you don#t need to guess
There is enough software on the market to do Glass design in all variations
Dont forget climatic load if you have insulated glass




best regards
Klaus

 

[ralphi]

For individual panels constructed of laminated glass sheets, horizontal shear transfer is imperfect. As such, you'll need to calculate effective panel thicknesses for strength and deflection. ASTM 1300 makes recommendations as does IStructE. Vertical, laminated glass in wind applications is usually treated as composite with neither glass layer considered sacrificial.

Kook. You only mentioned wind applications where the composite action of the laminated can work. What applications it won't work as composite? Most glass suppliers I talked to never use laminated glass in windows because it's more expensive and they all use tempered glass. But just for theoretical considerations. Let's say you have 6mm of tempered glass (6mm is standard for typical window size) vs 9mm of laminated glass (with two 4.5mm normal (not tempered) glass sandwiched together). If you hit it with stone.. what would be more resistant and which breaks easily? What kind of applications where the 9mm laminated only doesn't use composite action and only the 4.5mm is engaged.. versus the tempered 6mm?

For emergency fire entry of fireman in windows during fire.. the laminated glass not so advisable, isn't it?

 

[KootK]

What applications it won't work as composite?

Usually safety applications and/or conditions of high temperature and long load duration. Glazed floor applications are an example. There, even with the layers laminated, it is common to assume that some of the layers will break and therefore will not participate in resisting load in the ultimate limit state.

Most glass suppliers I talked to never use laminated glass in windows because it's more expensive and they all use tempered glass.

That's mostly been my experience as well. I've done some very tall, two sided support windows at the top of highrise buildings where tempering alone was insufficient at any reasonable, single lite thickness. While tempering helps with strength a great deal, it doesn't do anything much for stiffness.

If you hit it with stone.. what would be more resistant and which breaks easily

Let's compare 9 mm tempered versus 2x4.5 annealed and laminated. I would expect the 9 mm tempered to be able to withstand a much greater load prior to first shatter. However, post-breakage, I would expect the laminated glass to perform much better from a safety perspective as it would tend to hold together well. It depends on what manner of resistance one is seeking in a particular application. First shatter isn't everything.

What kind of applications where the 9mm laminated only doesn't use composite action and only the 4.5mm is engaged.

Under the right temperature and load duration conditions, the laminated glass can be relied upon to behave compositely. That is, until, one or the other layer is shattered by impact. It's only when one layer must be assumed to be shattered in this way that non-composite behavior comes into play.

For emergency fire entry of fireman in windows during fire.. the laminated glass not so advisable, isn't it?

I've not encountered that as a design criterion myself but I can see the logic in it. I've witnessed testing on glass laminated with SGP. Even with all laminations shattered, it holds together remarkably well. The only realistic way through would be to knock the glass out of it's support framing entirely. Lesser interlayers are probably a bit more amenable to through traffi.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[ralphi]

Usually safety applications and/or conditions of high temperature and long load duration. Glazed floor applications are an example. There, even with the layers laminated, it is common to assume that some of the layers will break and therefore will not participate in resisting load in the ultimate limit state.
..
Vertical, laminated glass in wind applications is usually treated as composite with neither glass layer considered sacrificial.

Why do you say that composite action is weak in long load duration, and composite action in short load duration like wind application can work? Any theoretical explanations, maybe the bond to the pvb in middle can encounter short duration flexure or shear?

 

[KootK]

Why do you say that composite action is weak in long load duration, and composite action in short load duration like wind application can work? Any theoretical explanations, maybe the bond to the pvb in middle can encounter short duration flexure or shear?

1) That's what the design standards imply.

2) That's what the available research tells us.

The fundamental "why" of it is beyond me I'm afraid. For reasons that material scientists understand and I do not, the inter-layer softens with temperature and creeps with time.



I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[ralphi]

1) That's what the design standards imply.

2) That's what the available research tells us.

The fundamental "why" of it is beyond me I'm afraid. For reasons that material scientists understand and I do not, the inter-layer softens with temperature and creeps with time.

For fire barrier, any idea how many degrees before the normal glass, tempered glass and laminated glass break? Have you come across say pyrex glasses (or other fire rated glasses) used in windows that are resistant to fire (where they use such glasses in labs in beakers, test tubes or flask)?

 

[KootK]

I haven't yet been involved in any mission critical fire glass design. I'd have to look all that stuff up.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[KootK]

Stumbled upon this and thought of you ralphi: Link

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.