A plasticity model for the behaviour of footings on sand under combined loading

A complete theoretical model is described for the behaviour of rigid circular footings on sand, when subjected to combined vertical, horizontal and moment loading. The model, which is expressed in terms of work-hardening plasticity theory, is based on a series of tests specifically designed to allow evaluation of the various components of the theory. The model makes use of the force resultants and the corresponding displacements of the footing, and allows predictions of response to be made for any load or displacement combination. It is verified by comparison with the database of tests. The use of the model is then illustrated by some demonstration calculations for the response of a jack-up unit on sand. This example illustrates the principal purpose of the development, which is to allow a realistic modelling of foundation behaviour to be included as an integral part of a structural analysis.