what is the minimum number of reinforcement bars in a circular tie rod?

Question

I know that the minimum number of reinforcement bars in circular concrete section of columns are 6, is it the same for circular tie rod section?

Answer 1

if you mean a square section with circular or spiral ties, even though it is very uncommon for such a section to be built, I would put 6 bars.

Answer 2

The longitudinal reinforcement in a concrete column serves two functions - 1) to provide the required strength to resist the applied forces, and 2) acting as support for the transverse reinforcement (hoops/ties). The reason for the minimum reinforcement requirement is based on the latter, because, in general, a column is a compression member, for which the shear stress and buckling are the main concerns, which can be minimized/eliminated by providing the minimum amount of stress confining reinforcement - longitudinal bars and hoops (for circular columns).

If a column is mainly provided to resist tension, as tension ties/piles, the former reasons for requiring the minimum reinforcement are no longer exist, instead, you shall provide reinforcing with minimizing the potential cracks in mind, for which, there is no guidance exists, but to exercise by the engineering judgment at a case by case base - a single steel rod encased in the concrete protective layer is acceptable in the non-corrosive environment, but more bars are needed otherwise.