please give me guide line of designing of curved elements or plates in Staad Pro...
There are some limitations on the use of Curved beams, you can find the same in the following linkhttp://communities.bentley.com/products/structural/structural_analysis___design/w/structural_analysis_and_design__wiki/8353.limitations-of-the-curved-beams-in-staad-pro-tn
So, You could draw the profile of a curved beam by joining the series of small straight line segments. Staad cannot calculate the section forces at intermediate section locations of a curved beam and hence if you generate the profile by joining the straight line segments then Staad would be able to compute the forces not only at the end nodes but also at the intermediate locations of those segments. So, the design could be performed at all the end and intermediate locations of every line line segments. To draw the curved line profile you may use the radial grid system.
Hope this helps you.
RAJAT