I am designing a roof structure which is about to be supported by a mezzanine platform. The whole platform is supported on a anchor rod at different locations It will be like, there are anchor rods at several locations on the mezzanine beam, which is hanging on the support of the anchor rod. How do I assign this support in STAAD ?
The support choice is engineer's decision. From your description it looks like the platform is in hanging position with the help of anchor rod. Then depending upon the connection you make, you need to create support. There will be support in vertical direction for sure. For other directions & moment restraints you need to check with connections. Generally anchor rods are not designed for any bending moment. So you need to release moments at support. For shear in horizontal direction practical connection condition will decide the support type.
How about providing a master slave command at the top node of the anchor rod and making the bottom node as slave node. By doing this and releasing the moments at the top node provides a connection that transfers only the shear and axial loads.
Whether this could work?
Yes. It should work.