A stable structure is the one which remains stable for any imaginable system of loads.
Therefore, we do not consider the type of loads, their numbers and their point of applications to decide whether the structure is stable or not. Normally internal and external stability of the structure is checked. If it meets the criteria of stability then the structure is checked for the total degree of indeterminancy.
Stability of structures
Before we check the determinancy of structures, it is necessary that it should be stable first. The question whether it is determinate or indeterminate comes next.