Simplified Structural Analysis of Retaining Walls on Stepped Footings

Abstract

Stepped footings are often required for earth retaining structures to suit grade changes in the site. The behavior of walls supported on stepped footings is not well understood due to the presence of reentrant corners and double curvature. In this study, a large number of reinforced concrete retaining walls with different geometry are analyzed using the finite element method. The bending moments throughout the wall and shear forces at the support are determined and presented in a tabular format that is easy to use by practicing structural engineers. The results of the analysis showed that positive and negative bending moments can possibly exist in a retaining wall supported on stepped footing; hence both faces of the wall should be reinforced for flexure. Further, very high stresses due to shear and bending moment occur at the reentrant corner of the stepped footing. These forces, however, cannot realistically exist in thin reinforced concrete structures due to postcracking deformations. Therefore, structural design at such a location should be based on values of shear force and bending moment just off the reentrant corner, provided that proper detailing with diagonal steel reinforcement is utilized at the tip of the step.