I'm not a STAAD guy at all (I work for one of their competitors). But, since no one else is responding....
You'll have to model this using a mesh of plate elements. Though that may be more basic / obvious than what you were looking for. You can then use the plate force contours and such as the basis for your reinforcement calculations.... which I'm guessing you will have to do by hand.
Josh is right, thanks.
For step-by-step details go to Help – Application Examples - American Examples - Example Problems – 9. Modeling slabs and shear walls using finite elements. It should be noted, that STAAD.pro has an alternative method where the slab can be modeled as a surface and then automatically meshed (which is excellent for complex geometry) but if you are new to working with plates, I recommend the former.
@ Josh & Seth, I thank you for your reply. Right now I'm am more familiar with etabs now cause I spent some time studying the video tutorial online. But my results is some what doubtful because when I run the analysis my upper column requires more steel compare to the lower column. It is very frustrating. I really dont know where do I made my mistake. Again thank you in advance.
