Columns: the minimum diameters of transverse reinforcement
Eurocode 2 part 2: Design of concrete bridge structures 9.5.3 (101)
The diameter of the transverse reinforcement (links, loops or helical spiral reinforcement) should not be less than Φmin or one quarter of the maximum diameter of the longitudinal bars, whichever is the greater. The diameter of the wires of welded mesh fabric for transverse reinforcement should not be less than Φmin,mesh.
The recommended values for the minumum diameters of transverse reinforcement are Φmin = 6 mm and Φmin,mesh = 5 mm.