Cyclic Axial Response of Single File

A number of solutions have been obtained for a typical offshore pile, to determine the influence of a number of the input parameters on the computered cyclic response. More significant parameters include the critical shear strain at which significant degradation of skin friction occurs, the rate of loading on the pile, and the distributions of static skin friction and soil modulus along the pile. The analysis predicts a gradual decrease in cyclic stiffness of the pile with increasing numbers of cycles and increasing cyclic load level, but a very sudden decrease in ultimate load capacity once the (half-peak-to-peak) cyclic load level exceeds 50% to 60% of the ultimate static load capacity. These theoretical findings are broadly confirmed by the results of small-scale laboratory model tests.