Overview
- Primary topic
- Laminated glass
- Engineering basis
- Equivalent thickness
- Review status
- Project-specific verification required
What VitraLab Uses
For laminated glass, VitraLab uses the EN 16612 Annex D equivalent thickness method. A laminated pane is not simply treated as the sum of its glass plies unless the selected shear transfer basis supports that behaviour.
Equivalent Thickness for Deflection
For stiffness, plate response, and deflection review, VitraLab uses the equivalent thickness value commonly written as heq;w. This value represents the laminated pane stiffness for the selected build-up and action basis.
Equivalent Thickness
Equivalent Thickness for Stress
For stress review, VitraLab uses the equivalent thickness value for the relevant glass ply, commonly written as heq;σ;j. This is why stress and deflection checks for the same laminated pane do not always use one identical thickness value.
Omega and Shear Transfer
The symbol ω, pronounced omega, represents interlayer shear transfer between glass plies. In VitraLab it is selected from the EN 16612 load-condition and interlayer-family basis: lower values mean less composite action, while higher values mean greater composite action.
kmod and Load Duration
kmod is separate from ω. ω affects laminated glass equivalent thickness. kmod is used for load-duration effects in the glass strength check, so wind, barrier, maintenance, snow, live, and permanent actions can have different strength-duration treatment.
Linear Response
In linear mode, VitraLab uses small-deflection plate response. For laminated panes, the relevant EN 16612 equivalent thickness values are used for stiffness, deflection, and stress review.
Nonlinear Response
In nonlinear mode, VitraLab uses the large-deflection response route where membrane behaviour becomes relevant. The laminated pane is still represented using the EN 16612 equivalent thickness basis, while the plate response is assessed through the nonlinear route.
Auto Mode
Auto mode starts with the linear response and moves to the nonlinear route when the deflection level indicates that large-deflection behaviour should be considered. This keeps ordinary cases simple while still flagging panes that need nonlinear treatment.
Applicability
EC10 and Enhanced Effective Thickness
The separate EC10 calculator is based on the reviewed 2024 drafts of prEN 19100-1 and prEN 19100-2. Where applicable, its Enhanced Effective Thickness (EET) method uses an action-specific interlayer shear modulus to calculate coupling, stiffness, equivalent thickness and ply stress. Calculated or Partial results can be compared with Full Shear and No Shear bounds. The source documents remain drafts and may change before final publication, so engineers must confirm the applicable edition, product data, assumptions and project requirements.
Engineering Review
The output should be reviewed with the project specification, support condition, load category, glass build-up, governing action, ULS stress, SLS deflection, and engineering judgement. This page explains the EN 16612 basis so engineers can understand which inputs drive the laminated glass stress and deflection checks.
Frequently Asked Questions
Does VitraLab use EN 16612 equivalent thickness?
Yes. For laminated glass checks, VitraLab uses the EN 16612 Annex D equivalent thickness approach.
Is EN 16612 equivalent thickness the same as EC10 EET?
No. The EN 16612 calculator uses the Annex D omega-based method. The draft-based EC10 calculator uses EET with an action-specific interlayer shear modulus and the selected coupling basis.
What is the difference between omega and kmod?
Omega is used for laminated glass shear transfer and equivalent thickness. kmod is used for load-duration effects in the glass strength check.
Where does omega come from?
In EN 16612 Annex D, omega is linked to the load condition and interlayer stiffness family. VitraLab uses that basis when calculating laminated glass equivalent thickness.
Can the user choose the load category?
Yes. The tool gives the user control over the relevant action inputs and duration assumptions, which should be selected to match the project basis.
Engineering content is prepared and maintained by VitraLab Engineering. Worked examples show how the current calculator treats a defined case; they do not replace project-specific verification.