A numerical model for the simulation of pile capacity degradation under cyclic axial loading

It is known from a number of field and model tests that piles under cyclic axial loading can exhibit a significant reduction of capacity compared to the static loading case. The main reason for this phenomenon is the compaction of the soil beneath the pile due to cyclic shearing. From the limited number of tests available, interaction diagrams have been developed, which give the number of load cycles leading to failure dependent on the mean load and the amplitude of the cyclic load portion, both related to the static capacity. However, such diagrams cannot account for soil conditions or pile geometry and pile stiffness. A generally valid calculation approach for the problem is not yet available. A numerical simulation scheme is presented, which allows the calculation of pile capacity reduction due to cyclic loading for a certain pile-soil system. The method is described in detail in the paper, and calculation results for piles embedded in sand are presented. Herewith, the quality of the method is assessed. Finally, recommendations regarding necessary further investigations and improvements of the method are given.