Why does some structural engineers disapprove Mindlin's Plate theory for the analysis of Laminated Glass 1

[ryan_struct]

I was going through this forum and learned that there are many structural engineers here saying that Mindlin's Plate theory is outdated, not accurate for the analysis of laminated glass. I've seen that SJ Mepla uses this theory to predict the behavior. I was wondering what are the issues or problems when using Mindlins Theory.

Also I have one more question, If I model a laminated glass In Strand7 with the stress strain curves inputted for each material including the laminate and do a non linear analysis , can I get an accurate result for the behavior of the glass?

What is the best method so far to accurately predict the laminated glass behavior under loads.

 

[JoshPlumSE]

I'm not sure that structural engineers are the most knowledgeable about analyzing glass. We want our structures to be ductile. Glass is very brittle.

Some possibilities about what people are talking about:
a) Midlin-Reissner plate theory is usually used for THICK plates because (as I understand) it handles the shear behavior better for thick plates.
b) Glass is usually a pretty thin plate. Maybe a return to the simper Kirchoff plate theory might be justified. Personally, I don't see Midlin Reisner as being any worse for relatively thin plates. But, there may be aspects that I'm not familiar with.
c) Particularly, I'm thinking about any geometrically non-linear aspects of a plate. Like larger deflections that get you into higher order effects.... Like a trampoline where the tension in the trampoline affects the out of plane stiffness.
d) Lastly, I wonder about places that the "laminated" glass may require a multi-layered plate element of some kind.

 

[3DDave]

Having looked at glass and glass failures, though not from stress analysis, glass is a nearly perfectly elastic material until it isn't.

What causes this change is that it is extremely sensitive to crack propagation. It's estimated that a freshly pulled fiber out of the glass furnace, and then cooled, has a tensile strength on the order of 1 Million PSI. But from the abrasion that a human finger touching it produces, that is reduced to around 5 KSI.

I would suggest that any laminated glass have outer layers that are tempered to prevent external abrasion from starting cracks in those layers, that the edges be protected by elastomeric isolation from being able to start cracks on the edges, and to keep the loads and resulting deflections very low.

It is also valuable to control the impurities in the glass. In particular a case a while back in which tempered glass tops for patio furniture would spontaneously explode because migration of iron atoms would eventually nucleate a large enough defect in the tensile pre-load section of the tempered glass thickness and act as an internal crack. This was thought to be accelerated by exposure to sunshine.