A little more information is required to definitively answer this question.. The form of the structure is important - is it acting more as a tension member, a compression member, a beam, an arch, or some combination? If we are talking beam structure, simply do what is done for externally prestressed concrete. Any number of standard texts will give you the solution.
I talk about (cable-strut structures) which are composed of only cables and struts. There are many possible configurations, here's one of them. The first figure represents the semi-open state, and the second one represents the fully-open state. The upper inclined cables are used as active cables that control the deployment process until the structure reaches the fully-open state. What i want to know is how to determine the amount of prestress required in these cables to stabilize the structure at the fully-open state?