RCDC Beam design - effective depth Calculation

Bentley Team,

How is the effective depth for beam being calculated for a beam with two or more numbers of layers in RCDC software?

Please provide the basis and validation for the same.

I could find some formula related to effective depth in FAQ in the link below, but that is not giving correct value for the design I have.

https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/41953/rcdc-beam