Sponsored by the Structural Engineering Institute where f cm, A k, μ, A sm, and σ n in Eq. refer to their respective counterparts in Eq. . It can be seen that Rombach’s formula is similar to the AASHTO one, but it does not take into consideration the internal friction of a keyed joint. It has been found that the application of Eqs. and leads to very different values for the ultimate shear