Abstract
No matter what external force is exerted to a stable truss structure, it can be stabilized without causing large displacements. This is the reason why it is called a stable structure. In the case of an unstable truss structure, however, it is not certain to support such forces in the initial configuration. It would probably change its configuration far from its initial state. The purpose of this study is to establish a simple numerical method to seek such an equilibrium stateof the unstable structure which is subject to arbitrary given forces. It will be also shown that each of member forces can be easily derived at the same time if the equilibrium state is obtained.
