Bearing Pressures for Rectangular Footings with Biaxial Uplift

Footings that are subject to axial load and bending can have a portion of their footing area that does not act in bearing. To design for such a loading condition, the engineer must compute the maximum bearing pressure, the bearing pressure at the remaining corners, the location of the line of zero pressure, and the percentage of the spread footing area acting in bearing. For footings subject to bending about both principal axes, the solution of this problem can be quite cumbersome and little design information is available to assist the engineer in solving this complex problem. This paper presents a solution to this complex problem, including the general principles and assumptions upon which the solution is based, the derivation of the equations used to solve this problem for any number of nonbearing corners, a design example using the derived equations, and a practical applications section, showing a sample computer application of the equations. This paper emphasizes practical design information for the practicing bridge engineer.