When a STAAD.Pro CE model (.std file) is analyzed, many files are generated. This is explained in-
(+) STAAD.Pro File Extensions - RAM | STAAD | ADINA Wiki - RAM | STAAD | ADINA - Bentley Communities
The attached .bat file can be downloaded and kept in a folder where you have the .std file. On running the .bat file (by double clicking it), the generated files can be deleted.
https://communities.bentley.com/cfs-file/__key/communityserver-wikis-components-files/00-00-00-00-54/CLEAN1.bat