External pressure stiffening ring

Yes, there is a strengthening ring on the GB150.3, the built-in and external circumstances, as long as the reinforcement of the moment of inertia can meet the calculation, that is

In principle, both built-in and external, but the specific depends on whether the built-in impact on the process. The tower has an inner support ring. The support ring, such as the whole ring, can be, if not the whole circle, I don't think it should be used as a stiffening ring