RAM Structural System - Load Bearing Walls supported on Concrete One-way Deck

RE: RAM Structural System - Load Bearing Walls supported on Concrete One-way Deck

Seth Guthrie — Fri, 16 Oct 2020 18:51:37 GMT

That's consistent with what you want, and probably fine for gravity walls above. If the walls above that transfer are modeled as lateral walls, then the diaphragm out-of-plane stiffness for lateral loads ought to be considered too. See this: https://communities.bentley.com/products/structural/structural_analysis___design/w/structural_analysis_and_design__wiki/18616.ram-frame-criteria-diaphragms#two-way

RE: RAM Structural System - Load Bearing Walls supported on Concrete One-way Deck

Alejandro Alvergue — Fri, 16 Oct 2020 18:25:18 GMT

Thanks Seth. I have changed those transfer slabs to "two-way" and now the reactions at the column I was checking, match pretty close to my calculations.

Regarding out of plane stiffness for a two-way slab. Note #3 under the one-way and two-way deck table (first link you provided) says

"The diaphragm will always be meshed, and out-of-plane stiffness will always be assumed under gravity loads."

This is fine for the gravity load cases, but when running lateral analysis (wind) in RAM Frame, and keeping all diaphragms as rigid, I would not want to include out of plate stiffness.

Your second link, mentions:

"For any transfer slab the out-of-plane stiffness should be considered when analyzing lateral load cases."

Though in RAM Frame, under Criteria>Diaphragm, I have purposely left the last box unchecked under "Include Out-of-Plane Stifness" so I would hope this stays true when the lateral analysis is run. Could you verify this?

RE: RAM Structural System - Load Bearing Walls supported on Concrete One-way Deck

Seth Guthrie — Fri, 16 Oct 2020 15:35:17 GMT

If the supporting deck is 2-way, then it gets meshed with and will support the walls above. If the deck is one way then there needs to be a beam (or wall) below the walls above to work. See also: https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/3262/ramss-two-way-decks-tn and https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/10202/modeling-podium-slabs