Ram SS Floor Vibrations

I would like to check floor vibrations using the AISC DG11 method in Ram SS. I have wide-flange girders, bar joists @ 24" o.c. and a 3" slab on 9/16" form deck. The program refuses to run and says that I don't have composite deck properties defined.  Form deck is non-composite.  Does Ram SS require composite deck instead of form deck?

Do I need to figure out a work-around for this?

Also, do I need to redefine my bar joists as simple spans?  I have 30" joist extensions (cantilevers).  Should I just have steel beam stub cantilevers 30" long every 24" O.C. or perhaps have a 30" deck edge offset?


Help please!

  • I can reproduce that warning in a model that has no composite decks. There is a simple work-around, however. Just add a composite deck property in Modeler - Property Table - Decking... You don't have to utilize the composite deck anywhere, just add it to the property set. Or you can always use that deck type on the floor and keep the beams (joists) non-composite.

    When you export to FloorVibe from a level with non-composite deck, you will have to specify average deck thickness, weight, and f'c, however. Vibration on a non-composite deck without any topping concrete is beyond the scope of Design Guide 11 (and probably just not an issue).

    Here's a note from the FloorVibe help:

    Total Depth is the height of the deck plus the concrete above the deck in inches.  The minimum thickness above the deck is generally 1 inch.  For composite construction, the AISC Specifications (ASD Section I5.1.5 and LRFD Section I3.5a) require a minimum of 2 inches of concrete above the deck.



  • It seems silly that all I needed to do was define a composite deck in the properties table to get the program to

    run and evaluate bays.

    How about the joist extensions? Should I delete the 30" joist extensions and use a 30" deck edge offset?

  • Joist cantilevers are going to cause you to get no design out of RAM SS and also will trigger an invalid bay warning preempting Vibration Analysis per DG11. They are important and ultimately have an impact on the frequency of vibration in that bay, but there is no way to use FloorVibe to check them.