Analysis of Footings Subjected to Biaxial Bending

Foundations of tall chimneys and towers, bridge piers and columns of multistory buildings are subjected to vertical loads eccentric about both axes of symmetry. The case of large eccentricities, where compressive stresses on the soil develop only over a portion of the area of the footing, was studied in the paper. A numerical procedure using successive approximations and based on Newton-Raphson's Method was developed to determine the maximum stress on the soil. The method is general and can be applied to any soil for which a realistic stress-strain relationship can be found. An illustrative example of a practical design problem was discussed. Three stress-strain relationships, namely linear parabolic and uniform, were used in the solution of the problem. It was shown that the maximum stress depends on the stress-strain relationship assumed for the behavior of the soil. The method may be applied also to study combined axial load and biaxial bending of columns made of masonry and other materials of negligible tensile strength.