How to know the value of selfweight of the structure in staad

You can create a load case and have the self-weight load assigned to the structure and subsequently you can look at the static check results for that load case which will give you the total weight of the structure.

You can create a load case and have the self-weight load assigned to the structure and subsequently you can look at the static check results for that load case which will give you the total weight of the structure.