Here are a couple of pointers
From the start up screen of STAAD.Pro, click on Configuration and ensure that the check boxes, highlighted below, are NOT checked.
Image may be NSFW.
Clik here to view.
Go to the STAAD.Pro input editor and replace all the SELF Y -1.0 commands with just one SELF Y -1.0 command. There should be no LIST at the end of this command which would ensure that the selfweight is assigned to ALL entities in the model.
Finally I would also like you to refer to the following post
