Bentley/RAM's website recommends using the deck gage thickness as the deck's effective shear thickness. However, the deck's attachment design, lapping, etc have a large effect on the deck's effective shear thickness and can dramatically change the building's behavior. Can you please clarify this recommendation? Was this meant as a simplification, and that detailed calculations on the deck's diaphragm stiffness are preferred? Thanks.
Our deck elements don't have a specific shear thickness, just an overall effective thickness. The thickness impacts out-of-plane flexure mostly (but also out of planes shear stiffness). Out-of-plane stiffness of semi-rigid decks is a topic discussed here: communities.bentley.com/.../ram-frame---criteria---diaphragms
Where it is to be considered, I prefer to make the deck thicker than the gage, so that out of plane behavior is more realistic and deflections are kept under control.