Laminated Glass Equivalent Thickness in EN 16612

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 h_eq;w. This value represents the laminated pane stiffness for the selected build-up and action basis.

Equivalent Thickness for Stress

For stress review, VitraLab uses the equivalent thickness value for the relevant glass ply, commonly written as h_eq;σ;j. This is why stress and deflection checks for the same laminated pane do not always use one identical thickness value.

ω (omega) and Shear Transfer

The symbol ω represents interlayer shear transfer between glass plies. In VitraLab it is selected from the EN 16612 load-condition and interlayer-family basis: lower ω means less composite action, while higher ω means greater composite action.

k_mod and Load Duration

k_mod is separate from ω. ω affects laminated glass equivalent thickness. k_mod 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.

EET and Future Upgrades

Enhanced Effective Thickness (EET), associated with newer Eurocode 10 / EN 19100 developments, is planned as a future upgrade area. VitraLab will not claim EET implementation until the relevant provisions, user feedback, and validation examples have been reviewed.

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