Slab stiffness properties

RE: Slab stiffness properties

Seth Guthrie — Tue, 25 Jul 2023 20:32:21 GMT

I tend to think of untopped roof decks as flexible. I like the pseudo-flexible diaphragm option.

For some guidance on the stiffness of semi-rigid diaphragms check: Example for Calculating Effective Elastic Modulus for Semirigid Diaphragms

The reduction factors are mostly useful when the calculated stiffness in orthogonal directions vary significantly.

RE: Slab stiffness properties

Nik — Tue, 25 Jul 2023 20:26:18 GMT

For an un-topped non-composite 1 way metal roof deck, how will these parameters affect the diaphragm in RAM frame? What modification factors will need to be applied?

RE: Slab stiffness properties

Seth Guthrie — Fri, 18 Jan 2019 19:58:58 GMT

From the RamModeler.pdf help file:

Stiffness modifiers can be used to modify the stiffness in different directions and actions (in-plane and out-of plane).
These can be used to assign different properties for corrugated decks such that load is only transferred along the deck direction. Similarly, they can be used to account for cracked properties of concrete decks (in place of crack factors). For noncomposite floor and concrete slab systems, you may also specify the angle from the global X-axis at which the stiffness modifiers act. To modify stiffness properties of diaphragms, the program allows you to define 3 stiffness modifiers for in-plane action (i.e., f11, f22, and f12) and 3 stiffness modifiers for out-on-plane action (i.e., m11, m22, and m12). Further information can be found in RAM Frame Manual, Section 6.24.