Punching shear calculation: the approximate values of β
Eurocode 2 part 1-1: Design of concrete structures 6.4.3 (6)
For structures where the lateral stability does not depend on frame action between the slabs and the columns, and where the adjacent spans do not differ in length by more than 25%, approximate values for β may be used (cf. § 6.4.3 for the definition of β).
The recommended values for β in the punching shear calculation are given in Figure 6.21N.