In staad pro why the self weight factor is always -1 in Y direction ?
" Factor = -1 & Direction = Y "
These are default value and direction. Command SELFWEIGHT Y -1.0 instructs STAAD.Pro to consider 100% of the DEAD Weight (weight of the structure) that is acting vertically downward. However, user has the option to change SELEFWEIGHT factor and it's direction of application.
So -0.8 means 80% of the Dead Weight ?
Correct.