Rigid Spread Footings Resting on Soil Subjected to Axial Load and Biaxial Bending. I: Simplified Analytical Method

A simplified analytical method that determines the axial load and biaxial moment capacities of a rigid spread footing of regular or arbitrary shape resting on soil is presented. Three different types of pressure distribution at the soil-footing interface are considered: uniform, linear, and parabolic. The proposed algorithm can be used to determine (1) the maximum soil-bearing stress under rigid spread footings subjected to vertical load and biaxial bending moments; (2) the vulnerability of exceeding the maximum soil-bearing stress by comparing the biaxial moment-axial load interaction diagrams of the footing with those of the attached wall or column; and (3) the development of nomograms for the analysis and design of spread rigid footings of different shapes. Three comprehensive examples are included that show the first two applications. The third application is shown in a companion paper that deals with development of design aids for the analysis and design of rectangular and trapezoidal spread footings. (C) 2013 American Society of Civil Engineers.