Maximum and Minimum Amounts of Longitudinal Reinforcement for Beams

If we assume that the mean modulus of rupture is 8 ′fc (which is certainly plausible given the data in Figure 5.6) and the effective depth d is 0.7 × the height of the section,

Cracking moment = ⋅ ⋅ = ⋅  ⋅16 1 6 0 7

b h f b d

r .