Cyclic Movements of Offshore Structures on Clay

A finite element procedure was developed to calculate small cyclic deformations of offshore structures founded on clayey soils and subjected to storm wave loading. The procedure requires data from cyclic triaxial or simple shear tests. The time history of deformations and the reduction in soil stiffness are given at any time or location. Although the procedure uses plane strain elements, it is also applicable to circular footings by conversion of the applied loads. The analytical solution was compared with two sets of experimental test results. The predicted deformations are in good agreement qualitatively with the experimental results. Quantitatively, it agrees well with one of the test results, while the other test indicates larger strains than are predicted by the analytical procedure.