Beams: the ratio of links in shear reinforcement β3
Eurocode 2 part 1-1: Design of concrete structures 9.2.2 (4)
The shear reinforcement may consist of a combination of: links enclosing the longitudinal tension reinforcement and the compression zone; bent-up bars; cages, ladders, etc. which are cast in without enclosing the longitudinal reinforcement but are properly anchored in the compression and tension zones.
At least β3 of the necessary shear reinforcement should be in the form of links.
The recommended value for β3 is 0,5.