Rogue Rings

[Drashner1]

Strictly speaking neither tensile strength nor compressive strength in excessive amounts would be necessary for the structure to exist in a meta-stable state.  

You could have such a ring made entirely of liquid, and it would be stable until something made a splash or a wave, and started the whole chaotic cascade that would end up, in following decades and centuries, in the whole thing coalescing into separate bodies ranging from planet-sized to black hole, many of them on collision courses with many of the others, and more than a few about to be ejected in random directions from the site.

You need active management of some kind to stop that from happening; a network of maglev tracks running around the thing might keep masses actively moving to maintain balance, concentrate mass where needed for gravitational adjustments, and, via momentum, lend some local rigidity to the structure.   This is one of those things that requires minimal energy if done to absolute perfection, but would be extraordinarily hard to do to absolute perfection.

With some magmatter supporting the track, or providing local rigidity to prevent certain kinds of collapse or imbalance, it would get easier.  As a practical matter, some magmatter would be used.  But it's hard to say exactly how much, because we're talking 'safety margin' here - if active management is done to perfection, it's not needed at all.  The question is how close to perfection can it be done?

Given that we explicitly describe Niven Clouds in the setting - as well as a topopolis filled with/made from water - it seems likely that Terragens are already experienced at stabilizing large ring shaped structures against their tendency to self-gravitate into a mess. On the flip side, given that we explicitly describe Banks Orbitals, World Rings, and Ringworlds as existing in the setting (and name a number of the former) we can also presume that magmatter as a source of tensile strength for large spinning structures is also routine. In the case of this structure it is the sheer size that is unusual, not the basic methods (assuming that scaling up this large doesn't take you into some new regime of instability challenges or the like (which it might but which we can't really say much about either as a practical matter).

I would expect that there would be some combination of active stabilization and magmatter supports in use (possibly along with other design elements), each most likely capable of holding things together on their own for some time simply as a matter of redundancy/safety.

Todd