Why Laminated Glass Needs a Coupling Model
A laminated pane contains glass plies separated by one or more polymer interlayers. Its bending stiffness and ply stress depend on how effectively shear is transferred between the plies. Treating the build-up as either fully composite or completely uncoupled can miss the intermediate response represented by the selected interlayer properties.
Equivalent Thickness in the Current EC10 Workflow
The implemented equivalent-thickness method converts the laminated build-up into response quantities suitable for the reviewed plate-calculation routes. The stiffness equivalent thickness is used for plate response and deflection, while ply-specific stress quantities retain the effect of the real laminated build-up.
Action-Specific Interlayer Shear Modulus
Interlayer shear modulus depends on the product, load duration and design temperature. VitraLab therefore requests Gint values for the active action categories rather than applying one value to every load. Permanent, wind, snow, live, maintenance, barrier and accidental actions can require different project or product data.
Calculated or Partial Shear Coupling
The Calculated or Partial Shear result uses the selected action-specific interlayer input to evaluate the intermediate coupled response. The reported coupling parameter, equivalent thickness and ply stresses belong to that action basis and should not be transferred automatically to another duration or temperature.
Full Shear and No Shear Comparisons
VitraLab also reports Full Shear and No Shear comparison scenarios. Full Shear represents the fully coupled bound, while No Shear represents uncoupled plies. These comparisons help engineers understand sensitivity to the selected interlayer assumption but do not replace verified product data.
Double and Triple Laminated Panes
The current implementation supports double and triple laminated panes. Triple laminated glass includes three glass plies and two interlayers, so the interface and ply response must be reviewed across the complete build-up rather than reduced to one governing surface without context.
Action Routes and Table A.1
Where the reviewed prEN 19100-2 Table A.1 route applies, VitraLab uses the implemented coefficient mapping. Reviewed fallback response routes are identified separately in the result so engineers can see how the structural response was obtained. A fallback route is not presented as direct Table A.1 coverage.
Ply Stress and Governing Resistance
The calculation retains signed stress for every laminated glass ply. The report identifies the governing ply used for resistance verification while still presenting the other calculated ply stresses. This helps distinguish the governing resistance check from the complete through-thickness response.
Engineering Review and Draft Status
The 2024 prEN 19100 documents are drafts submitted for enquiry and may change before publication. Engineers must verify the interlayer product data, temperature, duration, glass treatment, supports, loads, consequence class, response route and all reported review notes against the project requirements.
Frequently Asked Questions
What is EET for laminated glass?
EET is an equivalent-thickness method used to represent the stiffness and ply-stress response of a laminated glass build-up while accounting for the selected degree of interlayer shear coupling.
Why does VitraLab request different Gint values by action?
Interlayer shear modulus depends on load duration, temperature and product data. Different actions can therefore require different values rather than one modulus for every calculation.
What do Full Shear and No Shear mean?
Full Shear is the fully coupled comparison bound. No Shear is the uncoupled-ply comparison bound. The Calculated or Partial result represents the selected intermediate coupling basis.
Does the current implementation support triple laminated glass?
Yes. The current EC10 implementation supports double and triple laminated panes and retains the calculated stress for every glass ply.
Is the EC10 laminated-glass calculation based on a final standard?
No. It is based on the reviewed 2024 drafts of prEN 19100-1 and prEN 19100-2. The calculation and its inputs require engineering review and must not be treated as certification to a final adopted Eurocode.
Can a generic interlayer modulus be used for every project?
No. Engineers should use verified product data appropriate to the action duration and design temperature, and review any conservative fallback assumption explicitly.