ABSTRACT
The Ac approximately equals to V/qn,where qn is nominal bearing resistance of the soil. Because settlement generally controls the size of shallow bridge foundations on competent soils, the ratio of Ac to A is typically much less than 1. So the rocking moment capacity approximately equal to V*Lf /2 and is insensitive to the ratio Ac/A. Figure 1 illustrates the concept of critical contact length, Lc, which equals Ac divided by footing width.
